Brief context: 1989 Itasca Suncruiser, 454, P30.Recently installed alternator - seems to work great. Recently installed carb - see the problem below:
Disclaimer: I am not a mechanic; but usually can figure stuff out by sorting through hours on Youtube, in forums, reading, etc.
The Problem: Installed rebuilt Quadrajet carb and new associated vacuum lines. Now starts and immediately stalls, accompanied by intake backfire/popping.
Diagnosis?: From my naive perspective seems to be a fuel starvation/extreme lean mixture issue. So I am trying to diagnose/check potential causes of such.
More background: Engine was running "OK" prior to new carb. I.e., would get me down the road; but could not resolve extremely high idle so figured replacing old/grubby carb/choke prior to heading out for NH-CA journey a good idea. Looked easy enough, and for most part went as expected.
One issue/caveat - had to cut fuel intake to remove old carb. Now finding it difficult to find something to make the U-turn into the fuel intake filter without kinking. Currently using about a foot of flexible 3/8 spectra fuel line; but not super pleased with set up.
-I have capped vacuum ports to try to isolate possible cause lean mixture.
-New idle mixture screws seem set in midrange (3-4 turns out).
-Have tweaked new choke adjustment to start at point just begins to open.
-Have confirmed accelerator pump pushing strong stream of fuel into both primaries with engine off.
Again, my best naive guess is something is causing fuel starvation right after startup. This was not an issue prior to new carb, so not sure what think. Am looking for list of what to investigate. Any logical suggestions appreciated. Thank you.
Did you clean the gasket mounting surface on the intake manifold clean and use a new carburetor mounting gasket? Same with base of carb, cleaned of all old gasket? Sounds like a vacuum leak. 4 turns out is probably pretty rich but that will not make it stall instantly. Did you reset the float level? Did you put the fuel filter in the carb inlet in the right direction? It can be installed backwards.
The only thing I can think of is the seal between the intake manifold and the base of the new carb..If there is gap or a bad seal between..that would let in plenty of air..causing the problems you are having
Rick..you type fast!! You beat me!!
Quote from: Rickf1985 on October 03, 2019, 11:01 AM
Did you clean the gasket mounting surface on the intake manifold clean and use a new carburetor mounting gasket? Same with base of carb, cleaned of all old gasket? Sounds like a vacuum leak. 4 turns out is probably pretty rich but that will not make it stall instantly. Did you reset the float level? Did you put the fuel filter in the carb inlet in the right direction? It can be installed backwards.
Thank you for your quick reply.
I did clean mounting surface and used new gasket. I did not reset float level. Presumed it was set properly by carb rebuilder (I purchased rebuilt quadrajet). I have not yet confirmed fuel filter is in correct direction; but it was on my list of today's todo's.
I also am suspicious of vacuum leak. Given that I have blocked off ports, I will probably unmount carb and double check gasket/surface. I thought I was careful mounting.
Was tempted to attempt to id vacuum leak via carb cleaner spray outside; BUT, the backfire through intake makes me nervous as I would not want vaporized spray outside intake/carb to explode :-(.
Quote from: RockwoodMike on October 03, 2019, 11:03 AM
The only thing I can think of is the seal between the intake manifold and the base of the new carb..If there is gap or a bad seal between..that would let in plenty of air..causing the problems you are having
Rick..you type fast!! You beat me!!
Thank you. Seems it is worth a double check. Is it possible to tighten on gasket too much? I thought I was careful; I did not ream on it; but something clearly not right.
It is VERY possible to over tighten it! Especially on a quadrajet where the two bolts got through the entire carb. You say you blocked off vacuum ports, let me ask you this, do you still have all of the emissions equipment on this engine? There are several vacuum sources going on here.
You say you bought this as a rebuilt carb? So you did not rebuild your old carb? I would not get into the carb but I would take it back. There could be major issues and you could void any warranty by taking it apart and then you are stuck with it and I am guessing you had to turn in your old carb as a core so that would leave you with nothing.
Quote from: Rickf1985 on October 03, 2019, 11:28 AM
It is VERY possible to over tighten it! Especially on a quadrajet where the two bolts got through the entire carb. You say you blocked off vacuum ports, let me ask you this, do you still have all of the emissions equipment on this engine? There are several vacuum sources going on here.
Good question.The original emissions equip appears still in place. (I also recently replaced all four belts, fun times...) The vacuum lines do make up a bit of a spider web :-(. I capped the ports on the carb, presuming that would be most effective way of making sure no leaks.
Quote from: Rickf1985 on October 03, 2019, 11:32 AM
You say you bought this as a rebuilt carb? So you did not rebuild your old carb? I would not get into the carb but I would take it back. There could be major issues and you could void any warranty by taking it apart and then you are stuck with it and I am guessing you had to turn in your old carb as a core so that would leave you with nothing.
Yes, I bought rebuild online from seemingly reputable shop. At time, I just thought more likely to get it right, and with quick shipping it was time efficient (so I thought).
I was supposed to depart for NH to CA this week (I am spending winter in Death Valley, volunteering for national park service. Did same gig in this rig two years ago.). I am supposed to be in CA in a week. Not likely now. Which means I will not arrive for my winter gig on time. Big bummer.
I still have the old carb. They give me a couple weeks to return core... Also have thought about re-installing it to see if having same issue...
Reinstall old carb, Solving a high idle is much easier than diagnosing a quick stall/ fuel issue on an unknown carb. You probably only need a new choke pot on the old carb. Where are you located?
One thing you can try is to plug all of the open vacuum lines also and try to start it.
Quote from: Rickf1985 on October 03, 2019, 11:52 AM
Reinstall old carb, Solving a high idle is much easier than diagnosing a quick stall/ fuel issue on an unknown carb. You probably only need a new choke pot on the old carb. Where are you located?
Ironically, I originally presumed it was choke (still think it was); but I thought I was being extra proactive by replacing entire carb, including new choke.
My concern now is that I have accidentally changed something. OR, maybe my jury-rigged fuel intake line is creating supply issue. It "looks" ok; but I wish I had been more persistent at getting line separated from old carb without cutting it. I eventually got the fuel line stub apart from the fuel filter housing once off the engine, but it was very difficult.
But yes, I am having some remorse about trying to be extra proactive, when I might have been able to just resolve high idle more simply. I will spend afternoon re-installing and hoping it returns to that problem... but something in my gut says it might not... :-(
I am currently sitting about 20 miles from Keene, NH, at my folks.
Quote from: Rickf1985 on October 03, 2019, 11:53 AM
One thing you can try is to plug all of the open vacuum lines also and try to start it.
Never thought of that... can open lines, not ports, impact what is happening inside carb? Certainly willing to try anything that simple at this point. thx.
While cutting the line was not optimal it is not a disaster. Use high quality fuel injection line that will slide tightly over the original line and clamp it with quality clamps. That will not cause an issue.You can use some Permatex #3 gasket sealer on the base gasket since it is going to be reused and that will make sure it seals. Do not use too much, a thin layer is good. Keep this stuff around as it is a good all around sealer. I use it in all paper type gaskets in addition to all radiator and heater hoses. It not only seals the hoses but it prevents the inevitable corrosion on the water neck of the thermostat housing. It also makes it a LOT easier to remove the hoses when the time comes.
Any vacuum leak on the engine will impact the mixture coming into the intake manifold
I was just thinking of something, is the choke closing on the new carb? Is it staying shut when you start it and is it stalling with it shut? That is an indication of not enough gas in the float chamber. Either bad fuel pump, clogged filter, bad float setting, etc. Since you had none of these issues with the old carb I am going to say it is the carb that is the issue as long as the choke is closing when you get the stalling.
Quote from: Rickf1985 on October 03, 2019, 12:11 PM
I was just thinking of something, is the choke closing on the new carb? Is it staying shut when you start it and is it stalling with it shut? That is an indication of not enough gas in the float chamber. Either bad fuel pump, clogged filter, bad float setting, etc. Since you had none of these issues with the old carb I am going to say it is the carb that is the issue as long as the choke is closing when you get the stalling.
All of your comments are helping me think through things. Thank you. I ordered a new gasket; but cannot pick it up until tomorrow. Will pick up some of the sealer you advise.
choke looks closed. in fact I can only open it part way via manually operating choke, so was wondering if after I resolve lean start issue, if I am going to have a problem when it is supposed to be wide open...
My issue with the fuel line is getting something to flex around the necessary U-turn heading into the fuel filter housing. Everything wants to kink. I tried bending some copper line; but both tries failed. The current spectra is my second hose attempt; Going to see what results from re-installing old carb... If I have this new issue then I created it...
after I first try starting with lines capped...
The rubber line should not kink if you give it enough room, you will have to cut the metal line back further . I am assuming you cut it close to the carb so go back about 6 inches or so and cut that much more off towards the fuel pump and then bridge that with the rubber line. If you find a junkyard in your travels just scrounge a new line off of any big block with a carb and a fuel pump. If you are trying to make your own line you need a tubing bender to prevent the kinking.
-I have capped vacuum ports to try to isolate possible cause lean mixture.
-New idle mixture screws seem set in midrange (3-4 turns out).
If your mixture screws are that far out, your running a rich condition! The screws should be unscrewed between 1-1/2 to 2 turn from fully seated for ideal fuel mixture.
yea, I kinked it even using a tubing bender... :-[ ... I like the junkyard option, eventually... good suggesting to cut the l back more on the fuel pump end. That should give hose some more room. Of course, getting to it deeper in will be fun... more goodies to remove/reinstall :-).
Quote from: BamBam on October 03, 2019, 12:30 PM-I have capped vacuum ports to try to isolate possible cause lean mixture.
-New idle mixture screws seem set in midrange (3-4 turns out).
If your mixture screws are that far out, your running a rich condition! The screws should be unscrewed between 1-1/2 to 2 turn from fully seated for ideal fuel mixture.
Yes; I do not disagree. But my symptoms seems to be too lean, so guessing not the idle screws...
The fuel injection line should be a bear to slide over the metal line but try to get at least a few inches of it on there. Use that sealer as a lubricant if you have to and I suggest using double clamps even though there is only 5 psi of pressure mainly because it is a gas line and the ends are not bulged out to hold it on. This is massive overkill but better that having it slide off.
By the way, A tip, wear mechanics gloves or nitrile or latex gloves when using that sealer because for some reason no matter how careful you are it WILL get on you and your tools. I don't care if the tools are across the room, it is magic, the sealer will find them! :)rotflmao Once on your skin there are only a couple ways to get it off. Carburetor cleaner, which is rough on the skin or it will wear off in a month or so. :D That stuff is one step above pine sap when it comes to sticking to skin! :)
Do not cut off more than you think you will need because contrary to popular belief metal line will not vapor lock as fast as rubber line. The black soft surface absorbs engine heat so try to keep it to a minimum.
Quote from: Rickf1985 on October 03, 2019, 12:37 PM
The fuel injection line should be a bear to slide over the metal line but try to get at least a few inches of it on there. Use that sealer as a lubricant if you have to and I suggest using double clamps even though there is only 5 psi of pressure mainly because it is a gas line and the ends are not bulged out to hold it on. This is massive overkill but better that having it slide off.
By the way, A tip, wear mechanics gloves or nitrile or latex gloves when using that sealer because for some reason no matter how careful you are it WILL get on you and your tools. I don't care if the tools are across the room, it is magic, the sealer will find them! :)rotflmao Once on your skin there are only a couple ways to get it off. Carburetor cleaner, which is rough on the skin or it will wear off in a month or so. :D That stuff is one step above pine sap when it comes to sticking to skin! :)
LOL... yea, my first attempt at a hose over metal line ended up gushing fuel. second attempt of slightly flaring end of tube, then double clamping worked better. Also, the rubber tube inside the spectra line (current setup) was MUCH tighter, and the clamps held - no leak. I am paranoid about fuel leaking, so I will get it... Orielly's had a bunch of Permatex choices, but no #3... I picked up some fuel resistant, but will see if I can find #3 elsewhere... oh, I still have some blue oil-based enamel under my fingernails from paint job a month ago... so I have also learned my lesson about gloves. :-)... good suggestion!... I had read about risk of rubber line vapor locking, so was another reason I was hoping to resolve using as little rubber as possible. Again, thank you for heads up.
Well, busy afternoon ahead. Hoping I make some diagnostic progress to my "I'll just drop a new carb in and hit the road" project... ha...
:-[ potential dumb question... is there a top/bottom orientation to the mounting gasket? Obviously there is a front/rear; but I did not carefully inspect/think about potential differences in gasket surfaces and mating to carb?...
Removed my new carb and compared new gasket to old and I do not see obvious differences in alignment, depth of grooves created, etc. But I also am not 100% what I am looking for.
I have a new gasket to pick up in morning; but re-installing old carb w old gasket tonight to see if I can get engine actually running again instead of immediate fuel starvation upon start up. (UPDATE: decided to wait for new gasket in morning)
On the bright side, removing/dropping in new carb process getting familiar. Too bad doing so seems to make me immobile :-(...
Quote from: Rickf1985 on October 03, 2019, 12:37 PM
...
By the way, A tip, wear mechanics gloves or nitrile or latex gloves when using that sealer because for some reason no matter how careful you are it WILL get on you and your tools. I don't care if the tools are across the room, it is magic, the sealer will find them! :)rotflmao Once on your skin there are only a couple ways to get it off. Carburetor cleaner, which is rough on the skin or it will wear off in a month or so. :D That stuff is one step above pine sap when it comes to sticking to skin! :)
Rick, is the Permatex type-3 you are referring to the stuff that is labeled aviation gasket maker?
Kind of a late answer but no, top and bottom are the same. You should see some imprint of how it was mounted on there. If you cannot see any imprint then you may not have had it bolted down tight enough and that may have been your problem. Using a 3/8 drive ratchet you should work in a cross pattern and bring it down to a fair tightness. Not really pulling hard on the wrench but a decent pull. There is a torque spec in the Chevrolet manual that I could look up or you could google it if you have a 3/8" drive or 1/4" drive torque wrench. Going to bed now. Will check in in the morning. Yes on the gasket sealer.
Quote from: Rickf1985 on October 03, 2019, 09:27 PM
Kind of a late answer but no, top and bottom are the same. You should see some imprint of how it was mounted on there. If you cannot see any imprint then you may not have had it bolted down tight enough and that may have been your problem. Using a 3/8 drive ratchet you should work in a cross pattern and bring it down to a fair tightness. Not really pulling hard on the wrench but a decent pull. There is a torque spec in the Chevrolet manual that I could look up or you could google it if you have a 3/8" drive or 1/4" drive torque wrench. Going to bed now. Will check in in the morning. Yes on the gasket sealer.
Thx... yes, imprint very similar to old gasket... your description of how I mounted is basically what I did. Also, I could not find torque spec in GM chassis manual; but yes, I did find some specs via google. Not identical, but very close... gradually (via cross pattern) work from about 3ft-lbs each to somewhere between 12-15. Makes good sense. I did finally find my torque wrench this evening. One more benefit of this fiasco :-)... I pick up another new gasket tomorrow... hope to at least get it back to prior condition... then re-start the process... that is my hope anyway...
thx again for help... I (we) will get this.
morning update:
picked up new mounting gasket... aim to re-install old carb to get engine running... while off I took a can of carb cleaner to it, and looked more closely at linkages, specifically choke (original suspicion of the high idle phenom that prompted me to decide entire new carb-choke install an good peace of mind idea :-( )
Well, the choke on old carb is very stiff, difficult to open, and just not right. Almost certainly the cause of the constant high idle before switching out carb.
Would like to address before re-installing (save yet another $10gasket, time, hassle). Really cannot work on choke while carb on engine. Just no room to manipulate.
My concern is, installing new choke on carb, getting linkage correct, etc., kind of looks more challenging than dropping in entire new carb (part of my original decision to replace dirty old carb setup). Plus, not sure I can find choke locally, so yet another mail order delay...)
Had I gone this route 10 days ago I'd likely be half way to California by now... oh well.
It is an electric choke right? Is it held on by screws or rivets? You should be able to get a replacement choke housing at any local parts store. There is very little to get "stiff" in the choke linkage. Can you tell if it is the linkage or in the choke pot? I always drill the rivets and replace them with screws after tapping the holes but you might not have the stuff needed for that. Once that is done the choke is adjustable. I don't like the engine screaming for long periods. I want the choke closed to get it started and run at high idle for a minute or two and then I kick it down and just let it idle for 10-15 minutes at idle to warm up. It is an RV, who is in a hurry?
Yes, the choke on old carb is held by rivets. New one is adjustable. I looked for parts locally and nobody seem to have the housing/thermostat, unless I did not ask for right part. But you are right inline with what I was hoping I could do... however :-).
When I got old carb back on, it did start up, without the lean symptoms, but it coughed and gagged and then stalled after a little bit, sounded like flooded... would not restart (flooded symptoms).
Took old carb back off and there was a pool of fuel puddled in the intake... I must have cranked it too long trying to get it to kick over... my bad.
Was disappointed it would not return to the original condition at least (high idle)... Am letting it dry out at moment. Going to try carefully re-installing new carb and see if I get any different results from my first attempt, in case I did not get good air seal. Not sure I am optimistic, but at this point I do not seem to have a running engine with either carb, although symptoms slightly different with each.
Oh, I ordered choke pull-off. The old one seems to be crapped out... Still, even by hand the choke plate over the primary is extremely stiff, almost stuck, on old carb. Very loose on new carb.
Maybe I just did not do a good job with my first attempt at installing new unit. Nothing obvious is apparent, but I hope it was me and my next attempt is more successful and it is not the rebuilt carb itself...
A guy has to have hope :-).
Oh, and soon, I will have a new party trick... the ability to uninstall, re-install a quadrajet blindfolded... :-)... well, except for that damn mini cotterpin over on the accelerator linkage... what a pain in the butt!
re-installed new carb second time... immediately started, stalled, backfire through intake with a flame that would make Gene Simmons proud...
called the supplier, shipping it back...
gotta figure out a plan B, with time of the essence...
Good thing Death Valley isn't going anywhere I guess...
Before re-installing old carb AGAIN, I studied the choke linkages, comparing the old to the new units. After about 10 minutes of poking around, I discovered the linkage on the old carb was not correct. A lever from pull off was in front, instead of behind choke lever. It was keeping idle plate nearly closed and "sticky." Figured out how to flip it.
Re-installed old carb... carefully... said an atheist prayer :angel: ... sprayed a little carb cleaner in to prime her, and...... she started up, coughed, and started idling!!!!!!!!!!!
I ran across the field with my arms raised like I just won Olympic Gold!!!!
now I better go double check everything... :-)
And there you go, you are now a bonafide, certifiable RV mechanic! :D If it was keeping the choke plate partially closed I would say your gas mileage should get a lot better, At least up to 7 MPG!
I've been following this throughout and have to say congratulations! Kudos for your persistence.
Ridingrambling, you are one who is not afraid to ask for help, accept it, try it and report back. Not to mention trying your own ideas as well.
Rick, as we all ? know is superior with almost any mechanical issue and many others as well.
Great reading and following of this topic.
Thank you both.
Did you take a video of your victory run?
Couple of thoughts, I know that bend you are speaking of well. I recently tried to replicate that hard tubing from the qjet down to the pump on my GMC. I failed miserably and just put the old one back on even though it has a decent kink in the line from a previous owner attempting to change the carb filter. If I wanted to redo it, I think I'd use a 90 degree flare elbow and a short piece of steel tubing to get in there close behind the carb instead of bending the tubing.
In order to disconnect that fuel line, for instance if I need to change the inlet filter, I found that it is necessary to take the four manifold bolts out and slide the carb backward an inch or so. First crack loose the fuel line with a wrench on the line and a wrench on the filter housing. Then crack the filter housing. Then pull the four bolts.
How is your in-carb fuel filter? If that plugs up you would have a fuel starvation problem. They are cheap, try changing it. Maybe you have contaminated fuel.
Also, don't rule out an Edelbrock 1411 with the necessary adapter plate #2696 iirc. Should be less than $500 total if you decide to give up on the qjet.
Good luck on your trip!
I have no problems getting my fuel lines off once the fitting is loose. I think his problem was that he could not get the fitting loose. The line only needs to move back 1/2" to clear the fitting. If you do not have line wrenches this can be an issue.
Quote from: Rickf1985 on October 04, 2019, 07:29 PM
And there you go, you are now a bonafide, certifiable RV mechanic! :D If it was keeping the choke plate partially closed I would say your gas mileage should get a lot better, At least up to 7 MPG!
7mpg would be a nice win :-)
Quote from: Rickf1985 on October 05, 2019, 08:49 AM
I have no problems getting my fuel lines off once the fitting is loose. I think his problem was that he could not get the fitting loose. The line only needs to move back 1/2" to clear the fitting. If you do not have line wrenches this can be an issue.
Yes; could not get the old fitting loose while carb installed. I eventually did get it off with the carb on bench... but it was very difficult. replaced with new flare fitting.
Quote from: tmsnyder on October 05, 2019, 07:13 AM
Couple of thoughts, I know that bend you are speaking of well. ... If I wanted to redo it, I think I'd use a 90 degree flare elbow and a short piece of steel tubing to get in there close behind the carb instead of bending the tubing.
How is your in-carb fuel filter? If that plugs up you would have a fuel starvation problem. They are cheap, try changing it. Maybe you have contaminated fuel.
Also, don't rule out an Edelbrock 1411 with the necessary adapter plate #2696 iirc. Should be less than $500 total if you decide to give up on the qjet.
Good luck on your trip!
My thinking was similar to yours, but I tried every automotive place within 30 miles and could not find a flare elbow or anything close :-(... I ended up using some flexible stainless covered hose ("Spectra" I think). Was a bear to get onto the steel line on fuel pump side because of everything in the way, but I seem to have it secure. Recreated the "S" turn and it is working without any kinks.
I did check filter on new carb. It was installed correctly.
I have considered converting to a different carb; but time and $$ both factors at moment. I know mine is still not working ideal; but I think it will get me there. When warm, I often get some dieseling, especially if I don't run 93octane. With local price difference between 87 and 93 about 70cents/gal, I just could not get myself to fill a 3/4 empty tank with 93. I have a 3000+ mile trek ahead. Plan is to run 93 when I get to mountains. If I need to I will get by with shutting down in gear. I'd MUCH rather get all the quirks worked out; but I also really need to get on the road. Unfortunately, my old carb does not have adjustable idle mixture screws OR adjustable choke. Those were two reasons I had decided to put new carb on. So my carb projects not done; but not now...
Quote from: TerryH on October 05, 2019, 12:23 AM
I've been following this throughout and have to say congratulations! Kudos for your persistence.
Ridingrambling, you are one who is not afraid to ask for help, accept it, try it and report back. Not to mention trying your own ideas as well.
Rick, as we all ? know is superior with almost any mechanical issue and many others as well.
Great reading and following of this topic.
Thank you both.
Did you take a video of your victory run?
Thank you.
This is a cool community. I had been lurking for a while; but had never posted prior to my frustration with this issue. I am super appreciative that Rick and others chimed in so quickly and helpfully. It helped me think through things, and also confirmed I was not crazy.
I will admit, for well over 1/2 century, I have felt completely clueless/inept regarding anything to do with engines. I have gradually been getting my hands dirty over past couple years on as needed basis. I still know very little; but each project gives me a little more insight, lessens the mystery, and gives me a smidgen more confidence I will get it figured out. It often takes a LONG TIME; but it still is satisfying. "Nice" thing about living in 30-year old Winnie is that there is never a shortage of projects to learn on :-)...
You should be able to run regular gas in that with no issues. If it is dieseling, (which is running on after shutting it off) then it is idling way to fast which is very hard on the transmission going into gear. If your definition of dieseling is actually pinging going down the road then the timing is off, advanced too far. Should be around 6 degrees with the vacuum advance line off and plugged and the idle set at around 650 RPM. You do NOT want to keep running it with it pinging since you are risking at least a blown head gasket or worse, burnt valves and holed pistons. There will be a diagram on the air cleaner that shows where all of the vacuum lines should be running. You might want to make sure they are all in the right spots.
It is dieseling sometimes... idle still a little too high, but not as bad as before choke linkage fix, and not every time. I still think choke needs repair. I will double check the vacuum lines. thank you.
Did you change spark plugs in this? Get OEM style plugs in it if not. If you did, make sure they are not plugs designed to run at higher temperature. They used to have plugs that would run hotter to keep them from fouling, maybe that's what's causing your dieseling.