Guys, I'm hoping someone has the answer for me. I'm in middle of nowhere Montana and have an issue with engine feeling like its running out of fuel... no power and acts like stalling when trying to accelerate or go up a hill.
Issue started around Chicago. Been fighting it since and it's worse... almost can't drive at all.
What I've done (before trip):
1. Dropped tanks and cleaned them.
2. All new rubber lines and clamps. Fittings cleaned.
3. New filters between tanks and selector valve.
4. New selector valve.
5. All new return and vent canister lines.
Started hesistating in Chicago. Had hard time making it through Wisconsin to Minnesota border where my family is. Changed the fuel filter in the carb and along the frame rail.
Ran fine for first 60 or so miles then started acting up. Very slow and hard drive to Rapid City SD.
Changed mechanical fuel pump with new one from Napa.
Today ran fine for 60 or 70 miles then started same thing again.
Stopped at top of a pass and cooled off. Bypassed selector valve with a piece of fuel line I had. No improvement.
Stopped at next chainup area and removed doghouse, breather cover and filter. Started engine and pressed the gas a few times then shut off.
Could hear gurgling in the carb.
Ran with cover off and doghouse off and seemed to run fine for about 5 or 6 miles. Tried putting cover on and problems came back. Tried running with doghouse on and cover off. Problems still there.
I am thinking because of the gurgling noise it might be vapor lock. Not sure the easiest way to fix that but need to figure this out ASAP before we head much further towards Alaska.
I will be much obliged to any help any of you can offer.
It may be your in-tank electric fuel pump. There's a way to jumper the relay that sends power to the pump, so you can run it without the vehicle running. Or you can do what I did which was to start the engine, then loosen the hose clamp on the pump side of the fuel filter which is on the frame. Without actually removing the fuel line, you will see that it will start squirting gas. If it does, push it back on and clamp it b/c the pump is working. If you end up pulling the line off, the engine is still running, and no fuel is coming from the tank then your pump isn't running. The engine has to be running for that pump to work btw, unless you do the jumper thing. You should also put someone on the key to shut off the engine if you happen to not be able to get the fuel line back on and it's spraying gas all over, unlikely though b/c it's low pressure on these old ones.
If the pump's not running, it doesn't mean the pump is bad. It could be the fuse, the relay, or the oil pressure switch. I believe the fuse and the oil pressure switch are in the area of the drivers side of the engine, and the relay is near the drivers feet. Mine was on the firewall behind the left headlight. It was nicely labeled in fact by HRC.
Good luck
You could be pulling air into the line from a loose connection somewhere if you do not have the electric pump in the tank. If you do have the electric pump and it is working then any loose fittings would be leaking and not causing this problem. Do both tanks have electric pumps? Does the problem exist and to the same degree on both tanks? If it does and the rear tank has an electric pump see if it is working and if it is then the problem is either a clogged filter or it is not fuel related. It could be ignition related, it could possibly be a bad ignition coil. I do not see many bad HEI coils but you are describing the symptoms of a bad coil. Could very easily be a bad ignition module also. The gas bubbling in the carb when shut off does not really mean anything, the engine is hot so it is going to bubble. Vapor lock occurs in the lines, not in the carb. If that is the original ignition module I would try that or at least get one to carry with you. Be sure you get the special compound for between the module and the distributor.
Any possibility of mixing up the fuel supply and return lines? Stranger things have happened...
They should be different sizes. If your generator has it's own line then the return line ends above the gas level so if they were reversed it would stall pretty quickly and not start again. The ones with the generator line tee'd into the return line are a different story as they go down to the 3/4 point in the tank but still are a different size than the supply line. The supply line should be 3/8" I believe and the return is probably 1/4".
Yeah, now that I think on it, you're right.
I really think it is fuel. Running with the air cleaner off and dog house off made a difference.
I bought some 2000 degree reflective thermoshield yesterday in Billings. Going to put that on in the morning before we pull out of Glacier. We'll see if that helps.
When it stalls on the steep grades, I have to crank it a couple of times before the accelerator pumps squirt fuel in. So pretty sure float bowl is empty.
My setup is:
70 gallon main tank with in-tank pump.
30 gallon aux tank with no pump
Main tank has new Holley regulator.
New selector valve.
It's all plumbed correctly.
Genny T's off the 1/4 return line above the differential. Valve at generator is closed.
It won't run off the aux tank for more than 20 miles, but then runs fine if I switch to main tank. This until the engine gets hot. Yet another indication (switching tanks) that it is fuel related. Also, stopping for 5 minutes to fill up results in it running a little better for about 10 miles (cold fuel load?) My brother says that the return fuel heats the tank and could be a contributing factor.
There's no parts store between here and Canada, so if it acts up I'll have to try to nurse it to Calgary.
It sounds to me like your mechanical fuel pump is bad. I know you said you replaced it but I have seen more bad ones our of the box than off of the engine in the last few years, Chinese specials. Without checking fuel pressure everything you do from here on out is speculation and you are just throwing parts at it hoping for the best. That is not a good plan or diagnostic procedure. You need to pin down the problem using tools, not guesswork before you get to a point where you need to be towed hundreds of miles! It does sound fuel related but you need to know what part of the system to change and unfortunately you cannot go buy the old fashioned ways of 'Well I already replaced the pump so it can't be that", Well, it can be. With the gas boiling in the carburetor one of the things I would look at and as a matter of fact I would be sure it is disconnect and wide open is the heat riser valve on the exhaust manifold. On most it is on the drivers side at the exit of the manifold and will have a vacuum tube coming up to the the engine ending next to the carburetor. Disconnect and plug that vacuum line and make sure you are getting equal exhaust flow out of both exhaust pipes. When that valve is closed it routes exhaust gas from the left side up through the intake manifold and over to the right side and then out. This is controlled by the TVS on the thermostat housing. As the water temp comes up it is supposed to open that valve but I have seen many stuck valves. It is not needed on a motor home since it is unlikely you are going to just start and run on a very cold day anyway. The engine will still warm up pretty quickly.
Thanks for the suggestions Rick. I am now positive it's not the ignition coil. Got one of those and installed at Calgary. Ran the same pulling out of there.
I am in Edmonton waiting for places to open. Fortunately the Walmart here has free WiFi.
It is definitely temperature related. We ran into a cold air mass and rain from Calgary north and it ran a lot better. I was able to keep up with traffic. But got worse again later when we drove out of that.
I had checked the exhaust valve (was able to operate it by sucking on the tube) when I had everything apart. But your point is valid I supose. I do know there is exhaust coming out of both tubes.
I've really been trying to avoid replacing carb. But if I have to, is there something that is bolt-on and easily available?
Any other tips welcome....
The only thing you are going to find that is a bolt on direct carb is another quadrajet. You may find one in one of the parts stores but they are going to want yours as a core and you have no idea of the condition of the rebuild you are going to get. You are probably going to pay upwards of 3 hundred for it when you could get hold of Sean Murphy in Ca. and get one of his custom rebuilds for the same price. At least then you know you have a quality carb. Or if you can find a Summit dealer in your travels you could pick up a Edelbrock 750 CFM Performer carb but you will need an adapter which may make your air cleaner to high under the dogbox. The Edelbrock carburetor number is a 1411.
There will always be exhaust coming out of both pipes but it should be equal, the valve blocks off about half of it. If you know the valve opens and closes then it is probably open. Pull the vacuum line of and plug it to be sure, you do not need it. Timing is done from underneath on the drivers side with the timing light hooked to #5 plug. Original spec is 4 degrees BTDC, I was running 10 BTDC and full manifold vacuum on the vacuum advance and I was getting just a tiny bit of pinging at 60 MPH. I would suggest to you to set the base timing with the vacuum advance off at at least 6-8 BTDC. You can try running the vacuum advance on manifold vacuum but since you are on the road I would say just leave it as is for now and play with it later when you get to where you are going. If your timing is 4 BTDC or less that will cause it to run hot at idle if the vacuum advance is set to ported vacuum. We are sort of crossing into a different set of posts here but this is still related to your heat issue. If you want to further discuss the timing issue lets do that by pm for now, otherwise we can continue with the other stuff as we were.
Changing the carb won't stop the boiling of the fuel in it. Have you tried insulating the fuel line from the pump to the carb? You need be make sure you have the correct fuel pressure to keep the fuel bowl full. What pressure did you set your regulator to? Does the tank pump work? I wouldn't use the original carb for a trade in if you decide to replace it.
By the way running the engine lean is causing more heat making things worse. You could be on the verge of burning pistons, destroying the engine.
I did try insulating the fuel line (mentioned in prior post) but it did not help.
I found a classic car shop here that is going to look at it. Hope to be on the road again by tomorrow.
They should have the smarts to rebuild your carb if needed and also know the timing tricks.
If it were me, I would start with simple. by-pass the selector valve and hook up the Aux tank only. Make sure it has at least 1/2 tank of gas. If your fuel pump is good then you should be getting fuel to the carb. Just to make sure, you said you put on a new fuel pump, the pump rod did not fall out and it is missing?
Is the carb filling with fuel and maintaining fuel. You said you change the carb fuel filter. Make sure it was the same size and installed in the correct direction?
If all ok here. then the engine should be running and maintaining fuel in the carb. You could check by disconnecting fuel line from carb and place line into a container, crank the motor and make sure the the pump is flowing fuel.
You said that it ran better with dog house open or when the weather was cooler. Are there any obstructions in the front , clogged radiator , cooling fans working?
JMO on my thinking and how i would go about it. Get it working this way and then tackle the rear tank.
I would be checking the ignition, especially the coil, and plug wires.
I have had the same weird intermittent issues with failing coils, and plug wires.
Coil heats up, begins to act silly, cools down, runs fine, then it does not.
Plugs wires exposed to heat around the exhaust sometimes act weird when they have been exposed to heat too much, and short out.
Had a Fiero that I had to change the plug wires every year, due to the heat under the hood. The Car ran flawless, other than that.
Coils, and plugs when failing can seem like fuel issues
Replaced coil, reply #8
Running better now. Electric pump in tank not.working. New electric on frame rail. Choke was sticking too and high idle and dieseling fixed.
We'll see. Ran much better yesterday.
All the ignition was new before I left except the coil and bite that's new as well.
P30 454 chassis rigs HAVE to have an electric fuel pump these days to prevent vapor lock due to the fuel that "they" sell us today.....
Quote from: legomybago on July 06, 2016, 12:59 PM
P30 454 chassis rigs HAVE to have an electric fuel pump these days to prevent vapor lock due to the fuel that "they" sell us today.....
After a year and 18k miles or so I have had no real problems on mine with just the mechanical pump on the engine, but at only 23ft long. It doesn't have all too far to go.
Your 87' should have an electric pump? Maybe it slipped through the cracks at the factory i??
I've discussed it before on another thread. Being an 87 yes it should, but our theory was they just left it out of the short one because it wasn't really necessary. I mean, my wheelbase is shorter than most pickup trucks. Did the 87 2500 w/ a 454 have an in tank pump, or was the pickup already on TBI at that point?
The Sub and pickup 454's were TBI then so I read.
Our 86' P30 ran good without the electric pump option 5 years ago when we first purchased it, then we started having vapor lock issues about 3 or so years ago. Went through the entire fuel system to verify correct, then installed an electric Holley pump. Runs like a dream climbing hills in 100* weather now. I sometimes will run it just on the mechanical pump, and it will do pretty good for a bit, but when you stop and fill the gas tank, then fire it up to head out, you are almost guaranteed vapor lock after heat soak.
As long as you do not have the monstrous 1/2" fuel line then a engine mounted pump will work fine on the shorter vehicles. On the really long ones if you have 3/8" line you may get by and 5/16 you will have no issues pulling fuel but getting enough fuel through that size line would be an issue. Once they went to the electric pump in the tank they went to 1/2" line and there is no way in hell you can pull from the tank with the engine mounted pump with that, too much air to absorb the vacuum before you can lift the fuel. Once the line is completely full of fuel with no air in it then you could do it but one big bubble hitting the pump and you are done.
Our 1985 chassis has the 1/2" supply line with mechanical fuel pump only from the factory. So at one time this system was good/ok other than the time it still took to prime the carb on cold start after setting. Who knows..... i??
This still isn't solved... Ugh.
Had trouble from Whitehorse to Dawson City. Was able to make it up the Top of the World and into Tok.
However getting to Fairbanks it was progressively worse.
In Fairbanks, tried moving the electric pump installed at Edmonton from along the front frame rail to back right above the fuel selector valve. No good. Couldn't get up the hill heading out of Fairbanks.
I took the car and went back to town and got a new electric pump (an SP8012, 5-9 psi) and put that on. Worked great - for about 20 miles, then it quit. Side of the road. Made to a spot I could pull off the highway fully. No pulsing on the pump. Voltage 12V when unhooked, 9 volts when hooked to pump. Took it off and back to Fairbanks in the car. No one had another SP8012 punp, so had to buy the only SP8016 (2.5 - 5 psi) pump. Back to the RV to install. Ran great for 30 miles then started behaving same again.
My setup is 2 tanks, through filters, through selector valve, to electric pump mounted right between the tanks. Then up the 1/2" line to the mechanical pump then to the engine.
It iw wired through a relay and 30A fuse, control for relay is the electric choke wire which is controlled by a oil pressure switch.
Not sure how I can be burning through pumps or if something else to causing this. This last time I was running on aux tank, so not pulling through broken electric pump in main tank.
Ideas? I'm at Denali and told there is a Carquest nearby, but not sure what they have in terms of parts yet...
If you have 12 volts with no load and 9 volts when turned on then it is not a pump problem it is an electrical supply problem. You have a major voltage drop somewhere in that line. What size wire are you using? Should be no smaller than 14 gauge at bare minimum. Could be a bad connection at the source of the wire also or it could be an overload since it is also powering the choke coil. You have the very same pattern no matter what you have tried with fuel pumps and it all sounds like the tank is going into vacuum. Have you put a NEW VENTED gas cap on there? I know you said you loosened the cap and it ran great for quite a while and then did the same thing. It is possible the cap ran itself in enough to seal as you drove. Try a vented cap. they are only ten or fifteen bucks. Or would have been down here anyway.
On edit, If the choke coil is only triggering th relay then that will not cause a voltage drop, check the power from the hot wire at the source through the relay to the pump.
OK, you are trying to fight or find the issue that you have. Start simple. Does you MH run on the AUX tank correctly? Like I stated before, start simple and then you can work on one thing at a time. You are stating that you have an in-tank pump. Is it still in the tank? Does it work? You say you put on a new fuel regulator. Is it adjust correctly? You said you have a new selector valve, but you stated you by-passed it. Is it hooked backed up correctly and is it operating correctly?
I ask this because you are now stating that you have another fuel pump in the system. You are adding more into the mix making it little harder for you to trouble shoot. You need to find out if you are getting flow from the rear tank. Set the selector valve for the rear tank. unhook the fuel line from the block fuel pump and see if you are getting the correct flow into a container. If you are trying to draw fuel through the in-tank pump, even though it should, it might not. There might be a chance that the fuel line in the tank on the pump may be bad.
I realize that a lot of this is disjointed and hard to follow, but if you read through all the replies, the info really is there.
1. Behaves the same when running on either tank. I know for fact that the valve is switching correctly and is not a contributor to this problem. Verified by running on each tank separate occasions and looking at which tank needed fuel to top off.
2. In tank pump in main tank is still there, not operational, so has to pull through it. No pump in aux tank. This is not an issue due to observations related to #1 above.
3. Bypassing the selector valve was 2 weeks ago when trying to diagnose the issue. It's been hooked up normally since Edmonton about 2 weeks ago.
4. The mechanical pump on the engine is working as the engine ran when the electric pump died, just couldn't keep up.
5. The external electric pump was added in Edmonton to try to solve the problem.
6. I have moved that pump to the back of the coach, mounted right above the selector valve. Inlet connected to the output of the selector valve, outlet connected to the 1/2" line that runs up front.
7. I just rewired it with 12 gauge wire to a relay at the front firewall. With the engine running (to establish oil pressure and engage the relay) the pump I have on there is pulsing.
8. I made a statement about the voltage at the pump only being 9 volts. With a good pump, running, it was really about 13.6 volts at the pump, 14.0 volts at the relay. So I think that 9 volt reading was due to a fried pump pulling excessive current. It's not the normal case and I doubt had anything to do with the pump failing.
So, where am I on this issue? I rewired the pump with 12 AWG wire. I replaced both as caps with new vented ones. I made it about 14 miles down the road and the alternator seized up. So I don't know for sure yet. Hope to be back on the road tomorrow when the new alternator arrives (that's a whole separate topic really).
Attached is a diagram of my current setup.
So, I looked over your posts, how long have you had your RV and have you driven it before you started having all the issues with the fuel. Sorry, I didn't know that your AUX tank is all the way in the back of your unit. In my 85 Elandan 34', my main tank is in the rear and the AUX tank is just in front of the rear tires. Still, the RV has 113k miles on it and I have all the paperwork and driving journal. It list every thing and mileage of when the PO had anything done. It doesn't have a electric fuel pump, just the mechanical pump on the block. The most that was done was they had replaced the clutch fan 5 times. So we know that for the most part the the unit run without an electric fuel pump, also by way that your unit doesn't have one in your AUX tank and it is further back. I would still say to start there, get your unit running on the AUX tank with no issues and then I would replace the in-tank pump. get your unit set back up to factory and you should be set. Looking at the way that the electric pumps are set up, is your oil pressure high enough to keep the pumps running or is the pressure switch working correctly.
Got the alternator replaced today and headed south towards Anchorage.
Fuel issue is not resolved, though it is cold and raining so that helps. I don't know if the colder air is helping fuel economy and that's why it's not so bad as when the air temp is warmer.
It was mostly just on a couple of uphill slopes. I did stop at top of one where the problem was and got underneath... the pump was chugging away.
At this point I wonder if it's just the size of fittings restricting flow. It's an SP8016 pump (http://ecat.spectrapremium.com/prod/SP8016 (http://ecat.spectrapremium.com/prod/SP8016)) with 1/8 NPT threaded connections. I have nipples in each going to 3/8 (inlet) and 1/2 (outlet) hose barbs into the rubber lines.
I will be in Anchorage in the morning so at least the choices for parts stores and parts availability will be better.
I can tell you one of the problems could be the location of the electric pump, it will not want too pull through filters and valves but since it also has the mechanical pump pulling with it that should not be an issue as long as the mechanical pump is working correctly.
Looking at the specs on the pump it shows 21 GPH, that is going to be pushing it on a hard pull up a mountain. 21 GPH is 1/3 of a gallon per minute. That is 43 2/3 Oz.s per minute. At WOT you are going to easily use more than that. I am using the lower end of the GPH scale since you are pulling through a filter and a valve which is going to put a hurting on a pump that is designed to be in the tank. Still, I think that with TWO pumps you should be able to pull it off, the fitting size may be a problem but there is not much you can do about it since the smallest fittings are the ones on the pump. You need a bare minimum of 3/8 opening all the way from tank to front pump and at least 5/16 to the carb if not 3/8.
My question for you would be when that shop looked at it did they check the carburetor. Mine did something similar to yours as you stated in original post and I found a carburetor guy to look at it. He found out by looking down the throat of the carb with it running that it wasn't getting as he put it enough squirt. So he took it apart ,new accelerator pump also metering rods fell out of air horn which he says is common on older carbs. He rebuild it to get us back home and it ran great after that. This was after new fuel filters new fuel pump new wires ,new cap and rotor. All these items may have helped but it was the carb the whole time getting progressively worse.
Ike,
Reasonable question. The mechanic did tune it up some - fixed the choke, adjusted the high and low idle.
I do know that it does run out of gas in the carb and I've had to either use starting fluid or dump gas into the float vent to get it going again. That is still suggesting a delivery issue.
Rick,
I think that may be my next option - bypass the filters and see if that helps. If it does, I'll put the one back in just ahead of the mech pump on the side of the frame. I still have spare filters (both frame rail one and carb one).
If not, I'll look and see if I can find a pump with bigger fittings.
I do still have to get back to NY in a couple weeks.
Also just for info when my carb was apart it had a bunch of charcoal in it, a new canister was put on along with a fuel filter on the vacuum hose going to the carb.
Brian, another path that you could go would to get a high pressure pump and install in between the main tank and the pressure regulator. It would be more back to factory spec other than having to pull through the in-tank pump.
Cook,
All that fuel line is inside the frame rail by the tank. Would hae to drop the tank to get to that. Not happening until I get back home.
So, I did as Rick suggested and bypassed the filter on the aux tank between the tank and valve with a piece of 3/8 fuel line I had on Sat morning. Ran fine on aux all way to Anchorage. I filled up there and drove out to Kenai River. There was a 4 mile long 5% or so uphill grade that it made pretty much just fine.
Going to find a piece of 1/2" line to bypass main tank filter before we leave Homer And see how it behaves on main tank.
Cautiously optimistic but not ready to declare victory just yet.
Cool, glad to see that you are running better. Like I stated back in post 13 and 28, would be best to start with simple and then work out through the bugs. What you have went through will only help improve things for the rest of us. As for me, when i drop my main tank, I will be putting in an access point to by-pass it should the same issue come my way. I am more looking to installing an external pump instead of the in-tank pump. I know that I could mark my floor and cut in an access port to get to the top of the tank like some have but I think that my water tank is mounted over top of where it would fall. You have a safe rest of your trip and I have enjoyed your link for the placed you have been. Thanks.
As you said you are going to make up the one to bypass the filter, I agree with that idea as long as there is one filter between the pump and the carb. I don't know what filters you have in there now but since you are "supposed" to have a filter before a gear drive electric pump I would use nothing more than a common inline clear plastic filter. They filter quite well, they are not restrictive and they are cheap. Run for a while as you are to verify the filters you had were the problem then put one of these in and see if the issue comes back, it should not. Here is a suggestion, Make this up ahead of time so if you have a problem you have it on hand ready to go.Make up a hose at least 3/8" t0o be able to bypass the electric fuel pump and all of the restrictive fittings associated with it. If you have problems again and determine it is not the filter then try that, the mechanical pump is more than capable of pulling the fuel from the tanks so that will not be an issue and this is not a vapor lock problem you are having so this will not change anything there. I think you may be starving the front pump due to those very small pump inlet/outlet fittings. The setup I would like to see is the engine pump and an inline filter between that and the carburetor. That is the ideal setup. If you are using an electric on the line then a prefilter is usually required to protect the pump warranty, I do not agree with pre filters since they restrict an already low suction pressure.
BrainB I see you made it back to NY. How did the rest of your trip go? Did you resolve your running out gas issue? I am making the same trip next year in our 89 chieftain and have been following your post. Any advice?
Im fighting almost identicle issues with my 79 P30 cruz air. Ive actually got a elec in line pump mounted near both tanks ran off relays that switch them on and off with the fuel selector valve, plus a HD elec in line pump after the fuel selector valve, plus a second new mechanicle pump. rerouted the fuel line out thru the wheel well area and tp the carb for less heat and removed all but one in line filter and it still starves for fuell to the point of quiting when its hot out. When it wits i can remove air cleaner and see fuel boiling in carb. Exhaust flapper is open but that stupic cross over heat in the intake i think is killing me. When its cold out its not nearly as much a problem as when its above 90 out. Much worse if i have to slow down or god forbid stop at a light as that causes it to boil again. All new hoses. tanks cleaned. Im thinking the fuel lines running down the frame rails near the exhaust pipe might be causing the gas to heat to the point of near vapor lock. We fought it all 3 weeks we were out this summer. My plan now is to replace the intake and carb with after market ones without the heat cross over port. Have to try and figure out what manifold to go with for Rv use, and am thining edelbrock carb, and while it apart might as well put in a better cam since 79 was emissioned to death and before they had a clue what they were doing. Anyone here have suggestions on intakes and cams?
Really would like to hear how the return trip went tho on this thread and what solved the problem finally.
Edelbrock Performer Plus package. You get the cam, intake and carb. Plus all the extras like cam lube and valve springs if they are needed. I don't think they are for that cam. The great thing about this kit is that it is a tested and proven setup that is designed to work together. You will get a better bottom end grunt and better midrange. Make sure you order a kit for no EGR to eliminate the crossover.
With the setup you have now are you using an isolator gasket under the carb or just a thin fiber gasket? You should have a insulator gasket that is about a 3/8" thick with spacers in the holes.
So far my initial searches for the performer plus package to fit a 79 P30 RV hasnt yielded much. Any leads on where to find them at Rick?
Quote from: crd on August 21, 2016, 12:49 PM
BrainB I see you made it back to NY. How did the rest of your trip go? Did you resolve your running out gas issue? I am making the same trip next year in our 89 chieftain and have been following your post. Any advice?
I never did resolve it fully. It comes down to the problem of using what was available off-the-shelf from the parts stores. The SP8016 fuel pumps readily available at Autozone etc can't pump enough fuel for the 454.
Now that I am home, I plan to drop the main tank. I am going to eliminate the in-tank pump and the external fuel pressure regulator. Then I am going to install a high-flowing external pump in the same position as the little one I have (right at the fuel selector valve between the two tanks.
I am confident that will solve all my fuel issues once and for all.
Brian, Just go to Summit.com and look for the big block Chevy stuff. It does not have to be for a P30.
Quote from: Rickf1985 on August 26, 2016, 12:20 PM
Brian, Just go to Summit.com and look for the big block Chevy stuff. It does not have to be for a P30.
Oh yeah... I know. That's the plan. JEGS has them also.
Just wasn't possible when we were on the road and in a different place every day.
Sorry Brian, that answer was actually in response to Kansascat.
Quote from: BrianB on August 26, 2016, 10:45 AM
I never did resolve it fully. It comes down to the problem of using what was available off-the-shelf from the parts stores. The SP8016 fuel pumps readily available at Autozone etc can't pump enough fuel for the 454.
Now that I am home, I plan to drop the main tank. I am going to eliminate the in-tank pump and the external fuel pressure regulator. Then I am going to install a high-flowing external pump in the same position as the little one I have (right at the fuel selector valve between the two tanks.
I am confident that will solve all my fuel issues once and for all.
Brian, i hope for your sake it does solve your problems, but you issues sound so close to what ive been fighting with mine for most of a year and three long road trips, with no success yet that i have my doubts it will. I now have 3 pumps pumping fuel no matter which tank im running on. A elec right next to the tank, a big high flow HD pump just after the selector valve, and the second new mechanical pump on the engine, and its still doing like yours is. Im down to just one in line filter between the big elec pump and the mechanical one. Ive tried eliminating the mechanical pump, then the big elec pump, no change. Ive bypassed the selector valve with no luck. rerouted the fuel line away from engine heat with no luck. Im down to replacing the exhaust system to move it away from the side the fuel lines run down, and replacing the intake to get away from the exhaust heat ports that run under the carb. Been the most frustrating problem ive encountered in many years of mechanics.
Kansascat - I had the "opportunity" to measure the fuel flow rate on the aftermarket "off-the-shelf" electric pump that I had to put on it. Only 1 gallon every 5 minutes. That's just 12 gallons per hour. Not anywhere near enough to feed the carb when the rig is only getting 7 mpg.
I am fairly confident that a better pump will solve my issue.
Your next move is to check the amt of fuel being delivered at the carb . If it is sufficient the problem is in the carb, Plugged fuel filter(inside carb ) Floats set way to low , Metering system inop ! Frank
Quote from: BrianB on August 28, 2016, 08:57 AM
Kansascat - I had the "opportunity" to measure the fuel flow rate on the aftermarket "off-the-shelf" electric pump that I had to put on it. Only 1 gallon every 5 minutes. That's just 12 gallons per hour. Not anywhere near enough to feed the carb when the rig is only getting 7 mpg.
I am fairly confident that a better pump will solve my issue.
According to my math, it actually ismore than enough fuel delivery. At 7 mpg, even if you were running 70 mph that would still only require 10 gallons per hour. Slower speeds would be fewer miles in a hour and even less fuel per hour. Just saying.
That 7 MPG is an average of light cruise where it is probably 12-15 MPG and acceleration where it is 2-3 MPG. I can assure you that at WOT it is in the negative figures at probably closer to 1/2 gallon per mile. Now think a half gallon jug of water and you are pouring it into a glass. Yup, about that fast!
Quote from: kansascat on August 29, 2016, 01:35 AM
According to my math, it actually ismore than enough fuel delivery. At 7 mpg, even if you were running 70 mph that would still only require 10 gallons per hour. Slower speeds would be fewer miles in a hour and even less fuel per hour. Just saying.
And how far up a 5% grade would you get before the float bowl is empty?
A fuel pressure gauge at the carb would be helpful.
Quote from: Froggy1936 on August 28, 2016, 01:24 PM
Your next move is to check the amt of fuel being delivered at the carb . If it is sufficient the problem is in the carb, Plugged fuel filter(inside carb ) Floats set way to low , Metering system inop ! Frank
Quote from: BrianB on August 29, 2016, 11:19 AM
And how far up a 5% grade would you get before the float bowl is empty?
Perhaps our issues are a bit different then, because mine starves out of gas while cruising on flat and level once its hot and starts doing its thing, yes, pulling a grade will make it also happen, but not only on a hard pull. I just installed a second carb base gasket, the thick ones, so have two of them under it. I doubt it will help really, but for $4 its worth a try. Ill prob find out this weekend. If it shows any signs of helping ill invest the 40 bucks for a thermal barrier one. I also unhooked the vacume line that operates the heat riser valve on the RH manifold which if i understand correctly will insure it stays in the open position...and its not stuck, i checked that. This thing is putting so much heat thru the passage in the intake its all burnt and crusty next to the carb on both sides. Anyone know just where to look and what to do as far as a egr valve. Not sure if its got one or not as i dont see anything that looks like what i used to seeing on others that have one.
kansascat, Like I told Brian, You need to remove all of the pumps that don't belong you are just adding to a mix that might not be balanced to run correctly. set it back up the way it should be, It ran before like it should, so if it does not now, need to think what you did before this started. Tune up done with correct parts. Was the timing changed and is it correct. Any bad vacuum lines. Plenty of air flow through the radiator. Clutch fan working correctly. All the fuel filter are fresh. Oil and Transmission temps are OK. All fuel lines are good and not cracked also in tank tubing. I would get the block off plates that you can install to shut off the cross over port in the manifold, they make a complete closure plate or a plate that has a small restriction and then see if you are still having a boiling issue before going out and getting a new cam/manifold/carb. JMO.
Just "T" into the fuel line near the carb and actually see what's happening with the fuel pressure as you drive. $27 at Hazard Fraught, probably a lot cheaper on sale.
http://www.harborfreight.com/fuel-pump-and-vacuum-tester-62637.html (http://www.harborfreight.com/fuel-pump-and-vacuum-tester-62637.html)
Not for permanent use!! Don't hook it up and leave it though, you don't want to plumb a pressurized fuel line into the cabin, just to troubleshoot.
Quote from: kansascat on August 31, 2016, 12:34 AM
Perhaps our issues are a bit different then, because mine starves out of gas while cruising on flat and level once its hot and starts doing its thing, yes, pulling a grade will make it also happen, but not only on a hard pull.
This is exactly what I am fighting right now on my FMC. A completely different animal than your rig, but same fuel starving issue.
I would do the same as cook elandan mentioned about only running one electric pump, and make sure all your rubber fuel lines are new, or at least inspected. We cured our vapor lock problem on our P30 this way. The fuel we get to run these days boils to easy.
I think ive pretty much covered the suggestions so far. Ill run thru it again for clarification. Fuel tanks have been removed...twice, and inspected for clean. EVERY rubber hose on the entire fuel system has been replaced with new, and good screw type clamps installed on every connection to insure air tight seal. Every filter was new, and now ive removed all of them ...including the one in the carb inlet, except one in line filter just ahead of the engines mechanicle fuel pump. One at a time ive tried only the mechanicle pump, and then only the big HD elec pump thats ahead of the mech pump, including bypassing the mech pump with the line. Ive replaced the fuel selector valve, and then bypassed it all together to see if it helped. It has fewer issues when running off the smaller aux tank which is just behind where the driver sits than it does on the factory mkain tank back behind the axle. It does better on the main tank since i put a in line elec pump back just ahead of it to push fuel forward, but still does it when hot. The exhaust system is in need of replacing as its got a few thin spots that leak as does the right side muffler. and the rear tanks fuel line runs inside the right frame rail which places it fairly close to the exhaust all the way forward. Its issues do seem to get worse the hotter the outside air temp gets, and its def worse in city traffic than on the open road. My current theory is the exhaust is heating the fuel coming from the rear tank as it travels thru the line so that when it reaches the carb its already pretty warm, and the rest of the problem, the majority of it, is the intake heat is over heating the gas once in the carb bowl. This is why i think its better on the aux tank as it reaches the carb a bit cooler than when on the main tank.
Everything on the engine was replaced when i first started restoring it from its 18 year slumber. All hoses, belts, thermostat, plugs wires cap rotor vacume lines filters and fluids. I removed the ac unit including the condensor so its getting great air flow thru the rad and usually runs below the center of the factory temp gauge and even on hard long pulls it rarely gets above mid point. Im running dual HD tranny coolers mounted just behind the grill and one of them i even added a elec fan on it so tranny seems to be running cool and happy. Ive made sure the heat riser valve is working freely, and now have it unhooked from vvacume even tho ive not seem it ever go to the closed position which is my understanding requires the vacume pod to pull it shut and that it defaults to open under its spring pressure with no vacume. When it has stopped running on me i have on a couple occasions coasted to a stop of wheezed to a pull off and shut it down and removed the air cleaner and witnessed the fuel boiling in the carb bowl by looking down the vent openings with a light, and noted at least on some occasions when i pumped the throttle it did not spray gas from the accelerator nozzles till a few pumps were made. Let it sit and cool a bit and it will retsart and run fine for a ways till things get heated up again.
Im running out of hair to pull out on this one. This weekend we plan to head out with it, and the only thing ive changed is to double up on the thick carb base spacer / gasket, and remove the vacume line from the heat riser, and adjust the timing a bit now that we are back to lower altitude. Sitting in the driveway its running great. It will actually spin the tires when power braked in my gravel drive. I think next will be a new exhaust since it needs it anyway. My only decision first is to install headers or not since it appears they will be needed to go along with the cam manifold and carb upgrade that will be coming. Any recomendations on a header model that fits and works well on these older P30's?
kansascat,
here is a quick trick that you might try, use this on my street racer. Make a coil of fuel line that you can get some good air flow around and attach it just before the mech fuel pump. so you are just making a gas cooler in a sense. some times at the track they are made where they fit in a large coffee can and you fill it full of ice just before your race. may be a way to cool your fuel down if that is an issue.
Well i kinda did to some degree, i removed the steel fuel line that GM runs up the front of the engine and across the intake to the carb, and ran a rubber fuel line from the mech pump out thru the fender well and up above the engine over the side right to the carb inlet. This way the line is in a cooler area not being in the engine compartment. I also bent the aircleaner intake hose as much as i could so its drawing most of its air in from that same wheelwell area rather then right next to but still behind the radiator so its getting cooler air. Im going to get some flex hose the right size and run the air intake in from up just behind the grill so it will get cold air completely. Good input tho. Thanks.
Time to stop throwing parts and find the problem. You have. no idea if your problem is fuel or electric. Put a pressure gage and find out if your getting fuel or not. If as I suspect (based on everything you have already done) you are getting plenty of fuel. Then you have to determine if the problem is in the carb or in the ignition.
So you're not trying to pull fuel through dead in-tank fuel pump? Thought I read that somewhere.
Could it be a heat induced ignition problem?
So I tried to read through all this to see if this was covered, but did you check the fuel filter in the quadrajet? When in first got my mh some one had put that fitter in backwards. The only way it ran was when there was enough fuel pressure to push the whole filter forward against the spring. It's also possible that it's just plugged...
He removed it already
Thanks. I must have missed that.
I still say put everything back to factory. It worked that way in the past. so now there is a problem that is in the engine area. Kansascat stated that he has leaky exhaust. I would put a heat shield down the frame rail to protect the fuel line. So for the most part with all that has been done to his RV the engine is good so the middle man is the carb. have it rebuilt.
Just had a quick thought, Kansascat could you exhaust be plugged up causing your engine to over heat more. That could put more heat near the fuel line and more heat internal through the crossover in the manifold. JMO.
I rebuilt the carb in order to get it running in order to bring it home when i got it. It shows no signs of having a plugged exhaust, in fact its got enough holes in it that id say its overly free flowing. LOL
I went ahead and ordered a set of hedman headers for it yesturday. Will install them and then it goes to the muffler shop to get a new Y pipe made for the headers where it will run down the left side to a muffler and then turn out ahead of the rear wheels. This way it wont even be close to the fuel line or main tank.
To address your question regarding it being electrical. I guess the main reason im thinking its fuel and not electrical is when it quits running, and i look in the carb bowl vent i see it boiling,AND it dont spray fuel when i pump the throttle like it should. Pump it several times and it will eventually start spraying fuel as it should.
Well, might as well drop in my 2p..
My 87 Chieftain 26RH had a very similar issue, felt a bit like a VW bus when she warmed up or was going uphill. As there aren't that many RV shops over this side of the pond, this little community helped a lot. Reading through many posts, I discovered that I had a couple of problems.
1st the 'auto retarders' .... not the ignition, but the exhaust valves, do stick closed (probably the cause of so many header issues) ... surprising how different she is, once that green idea was wired back at first, then removed when an exhaust specialist made me some custom connectors.. now that helped with the flow, but made the starvation a bigger issue.
The answer was to replace the fuel pump relay (NOT MANUFACTURED OR AVAILIABLE ANYMORE!!) so I had no choice but to disassemble it in its entirety.. This little beast from the 80's is a safety relay! very interesting! When you turn on the ignition it has a 10 second priming ON action then it turns off the pump. Then it waits for the oil pressure to rise whilst the engine is running, then turns on the pump again. The relay shuts off the pump if the oil pressure drops (i.e you have an accident). all of this is done using discrete components! so after fitting the reconditioned electronic relay I can hear a very quiet motor at the back when I turn on the ignition. Not only does she start a lot better when cold, she now pulls like a train..... but only when I can afford it over this side of the pond(almost $10 US gallon)!!!...... next project is to connect a 12" red lamp to the top of the dash flashing and sounding the alarm on the opening of the 2nd throttle!
Sounds like another case where a gauge would have been handy to troubleshoot the problem.
T in the gauge, verify that it has no pressure at the carb. Maybe it's the fuel relay? --> Jumper the relay to force the pump 'on' --> Pressure at carb? Y? ---> Bad relay.
But without seeing the pressure at the carb you're just shooting blind.
It may not be the pressure but the flow. They all say that the unit runs fine for awhile then the issue happens. There is a loss of fuel some where. Maybe there is a clog in the hard fuel line. Are you able to clean it out. With kansascat he has three pumps in the system, they may be working against each other. Didn't see where he say anything about a fuel regulator. Brian was trying to pull through a dead pump and regulator.
but I agree with tmsnyder along with put the unit back to factory and test the flow and pressure and that will take all of that out of the issue. I had said that on my 85 elandan, only had the mech pump with two tanks main behind rear wheels and aux mid driver side. no electric pump. PO kept good logs and never saw any comments about fuel issues. unit has 113k miles with dual exhaust headders and is 34' long. Air flow under the RV should be enough to keep heat away from fuel lines in the rail.
Quote from: kansascat on September 01, 2016, 10:57 PM
To address your question regarding it being electrical. I guess the main reason im thinking its fuel and not electrical is when it quits running, and i look in the carb bowl vent i see it boiling,AND it dont spray fuel when i pump the throttle like it should. Pump it several times and it will eventually start spraying fuel as it should.
Are you sure you have the correct size needle and seat in the carb? They do have different sizes. Is the float adjusted correctly? You need to run that bowl as full as you can because the Qjet has a rather small bowl to begin with. You also need 6 to 6.5 lbs of fuel pressure at the carb. You really should take the time to pull the top back off the carb to be sure the bowl has the correct amount of fuel in it.
I have already added my 30 cents but 6-6.5 lb.s of pressure is pushing the upper limits. It is doable but could possibly cause flooding under some circumstances.
A pressure gauge will indicate whether the flow is sufficient at all times and at all loads. And as Rick said, 6 psi is too much, carbs only want like 3psi.
Quote from: cook elandan on September 02, 2016, 03:07 PM
It may not be the pressure but the flow. They all say that the unit runs fine for awhile then the issue happens. There is a loss of fuel some where. Maybe there is a clog in the hard fuel line. Are you able to clean it out. With kansascat he has three pumps in the system, they may be working against each other. Didn't see where he say anything about a fuel regulator. Brian was trying to pull through a dead pump and regulator.
but I agree with tmsnyder along with put the unit back to factory and test the flow and pressure and that will take all of that out of the issue. I had said that on my 85 elandan, only had the mech pump with two tanks main behind rear wheels and aux mid driver side. no electric pump. PO kept good logs and never saw any comments about fuel issues. unit has 113k miles with dual exhaust headders and is 34' long. Air flow under the RV should be enough to keep heat away from fuel lines in the rail.
Quote from: Rickf1985 on September 05, 2016, 08:43 PM
I have already added my 30 cents but 6-6.5 lb.s of pressure is pushing the upper limits. It is doable but could possibly cause flooding under some circumstances.
Depends on what size the needle and seat are. If they are the stock .110 they will handle 6 psi. If they are the .125 he can get by with 5 psi. A big block should have a .125 needle and seat, but I don't know what comes in the kit now a days. Needles and seats used to be available up to about .150, not sure they're available any more. The float setting is very critical on the Qjet.
tmsnyder 3 psi is too low on fuel pressure for a Qjet, cant fill the bowel fast enough for a BB engine.
It is not pressure that fills the bowl but volume. Three lbs. is too little though. the specs. are 3.5 to 5. And that is all assuming you have good volume at the specified pressure.
Thought id share a update on my rig. We went on a 500 mile round trip over the holiday weekend and was pulling the car trailer with both my jeep and my sons bronco II on it down to southern oklahome to go off roading. Anyway the outside temps got up to about 90 and there are a few decent hills we had to climb. It ran real well the entire trip as long as i was on the aux tank, located behind drivers seat on frame, but would only run for a half hour or so on the rear main tank before vapor locking and trying to die. I feel this pretty much rules out it being a ignition issue as that wouldnt care which fuel tank it was using. The carb boiling and trying to die on either tank seemed to be fixed tho now. All i did to it before this trip was i added a second thick carb base gasket to help insulate the carb from the intakes heat, and i removed the vacuum lines that control the heat riser pod on the manifold and the air intake flapper in the air cleaner, and advanced the timing some since back to home elevation.
Im still pretty convinced my rear fuel tank issues are related to the exhaust being run so close to it for such a long distance, and aggravated by it having a few leaks from thin spots. The fuel line is quiet hot to the touch after having been run for a distance. Perhaps the alcohol fuels make it even worse, i dunno. Either way its going to get a new exhaust that runs down the left rail only so its not near the fuel line any more, and im upgrading it at the same time as the first step in my quest to find more ponies in the 454 for when we are in the mountains. My new set of headman headers arrived tuesday. I plan to have them buid a Y pipe to bring the two sides together just ahead of a new muffler, or get a 2 inlet muffler to bring both banks into with like a 3" outlet turned out the left side ahead of the rear axle. While im not a huge fan of headers due to the increased heat around the engine, especially the starter and plug wires, ill just have to make sure everything is well shielded and wires held up away as best i can. Next will be a cam intake and carb set from edelbrock. Once i have the new exhaust on it, i will try bypassing the mid point elec fuel pump, but i think ill keep the in line pump back by the rear tank to help push fuel to the main pump on the engine.
That is a hell of a load to be pulling behind you. All things considered I think you have the problem pretty much narrowed down. With the headers you will have less back pressure so there will be less flow back through the intake as a bonus, the problem is that the heads were designed for exhaust to get to the EGR valve so there will always be some there until you go to a Non-EGR manifold. I never paid attention to what size yours is but if you have a frame extension you better be sure it is very well reinforced at the extension joints. These were always a weak point.