Getting our 1989 Winnebago Warrior 22EC ready for the road...

[legomybago]

work....

Have a safe trip.

[engineer bill]

375 miles home. Ran great when vacuum was above 12.


Massive back-fires on any kind of slight hill unless I slowed way down to keep the vacuum up. A really long trip, limping home.

[Rickf1985]

Bill, Is this backfiring under load or coasting? And through the exhaust or carburetor?

[engineer bill]

Rick,


The back-firing is only under load. It appears to be through the carb - my coffee cup sitting on the doghouse jumps about an inch when it happens.


Bill

[Rickf1985]

OK, I was under the impression before that it was while you were coasting down a hill. This is more serious. It can be caused by a couple common things or a couple less common problems. Backfiring through the carb is usually caused by timing to far advanced or too lean of a mixture. It can also be caused by a burnt valve. Let's go with the first two right now since a burnt valve will usually give a miss and a steady pop-pop-pop at the intake. Have you had the timing changed recently? How is the idle? is it nice a smooth and at a fairly low RPM? It is possible that the advance weights in the distributor moved forward during high speed use and then got stuck there. That will give you advanced timing without ever having moved the distributor. The excessively lean condition is usually a vacuum leak under the carb or the intake manifold. Or a broken PCV hose . It could also be a clogged carb secondary circuit. What have you done to the engine right before this started? lets try to get this narrowed down to a sub-system.

BTW, Check your firing order 18436572, there is one crossed pair that will run fairly well but give the symptoms you have.

[engineer bill]

Rick, thanks for your interest and your last post on the back-firing problem. Here are my answers to your questions and a couple of comments and questions of my own.


Rick:  ... a burnt valve will usually give a miss and a steady pop-pop-pop at the intake ...
Bill: It is not missing. The noise at the driver's seat from the area of the dog house is blame-blam-blam. Its very loud. It continues until the vacuum comes back above 10.


Rick: Have you changed the timing recently?
Bill: No. But, I plan to have my shop inspect the timing, centrifugal and vacuum advance today.


Rick: How is the idle? Is it nice and smooth and at a fairly low RPM?
Bill: The idle is reasonably smooth. I had a lot of mechanical work done at reputable shop about 2000 miles/1 year ago. They set the idle at about 800 (per my dash tach). I always thought that was kind of high but let it slide.
Until now, it did seem to pull very strong up hill, even towing the Samurai.
The exhaust has always been really stinky - so bad that if I leave it running in the street, people complain. Other than all that, the idle is smooth and steady.


After pulling up at the house from this last trip, the idle was lower - about 600. It was back up to 800 when I re-started and warmed up the motor yesterday.


Rick: Backfiring through the carb is usually caused by timing too far advanced or too lean of a mixture ... It is possible that the advance weights in the distributor moved forward during high speed use and then got stuck there ... The excessively lean condition is usually a vacuum leak under the carb or the intake manifold. Or a broken PVC hose. It could also be a clogged carb secondary circuit ...
Bill: It's going into Danny's shop is a couple of hours. I'll ask them to look into this ... timing, vacuum leaks, hoses etc. I'll ask them to check the firing order too.


Some other folks have suggested burnt or damaged plug wires, cap/rotor damage, EGR valve, AIR Pump system problems -- in addition to vacuum leaks and ignition timing issues.


My own feeling has been that this is related to some failure in the emmissions control system.


Should I expect damage to the engine or carb from all this back-firing?

[engineer bill]

Rick: It could also be a clogged carb secondary circuit.
Bill: This could be it. Some folks have suggested this and also clogged fuel filter and fuel pressure issues...

I'll ask my mechanic to focus on vacuum leaks and ignition timing issues today.

[engineer bill]

Turns out the problem was melted spark plug wires...

My really great mechanic, mentioned in previous posts, Danny at All Flow in Martinez CA, replaced them with the correct high-temp ones. While he was at it he replaced the oil pan and transmission gaskets since both were leaking copiously. All three of these items had been replaced just last year by my old mechanic, Concord Coach, who used apparantly used Pep-Boy's wires and overtorqued both pan gaskets so that they were squeezed out the sides.

I've wondered and worried a little, will a lot of backfires like I had, damage the carb or the air cleaner?

[Rickf1985]

If you have the Quadrajet carb it is probably fine, I would run it and see how it runs. The Holley carbs had issues with backfires taking out the power valves unless a backfire preventer was installed in the carb base. Those wires must have been total JUNK!! I can see a miss but to cross fire like that.......................... JUNK, JUNK, JUNK!

[M & J]

Second what Rick said.

[engineer bill]

Well, thankfully it works fine now.
BTW, I do have the Quadrajet.

[engineer bill]

While I'm here...


The specs on my 1989 Winnebago Warrior 22EC say that I have a 40 gallon fuel tank. The Motorhome Manual says "fill is limited to 80-90% of total capacity". So, 80% of 40 would be 32.


My observation is that with the fuel level gauge needle on 'E' it takes only a little less than 32 gallons to fill and this would seem to agree with the manual.


The missing 8 gallons are a pretty big deal though, since if I only have 32 gallons, my range, with 20% reserve, = (100%-20%) x 32 gallons x 6-7 mpg = 154 miles to 179 miles, which is not much.

[Rover71]

Hi --Just re-reading your backfire issue. The problem we had several years ago was the opposite, got better under load. I have a fuel pressure gauge and the pressure had jumped to 10 PSI , carb float couldn't handle it and created several very loud backfires, I was afraid it would blow the muffler off!
Unplugged the fuel pump relay and drove home for 300 miles on the engine pump,no problems. Checking discovered that the pressure regulator had failed , was able to buy a kit for about $8.00 and install it without removing the unit, which would have been a big process.
While checking my present fuel starvation problems, I  did another kit replacement, diaphragm was quite hard, but wasn't the problem.
Turned out to be clogged in tank pump strainer after less than 2000 miles, I think we must have gotten some dirty fuel. The sock gets partially clogged, then sucks tight to bottom of pump, leaving only a penny sized surface, , not good.
Have a great day---Harv

[Rickf1985]

That is a good find and good info to have on here. There always seem to be fuel issues with these things and that is one I have not heard yet. A real bear to diagnose and find that is for sure! So if you are getting very low flow from your electric pump this is something to think about.

[engineer bill]

Rick,


I don't know for a fact that the backfiring was a plug wire problem rather than a lean fuel problem or an advanced timimg problem or any of the other suggestions.
We did replace the fuel pressure regulator diaphram and spring about 1500 miles back. (It had been leaking fuel from the regulator.)
The backfiring did first start after a long downhill section on a previous trip. On this last trip it pulled strong all the way up the Siskiyou Pass (4400'), got good and hot and then ran crappy after that. When we got home we did find the el-cheapo plug wires melted and replaced them with high temp parts.
Since then, I haven't driven it more than 25 miles up and down CA 4 near here and it seems ok. I've gotta be kind of careful here. My wife was traumatized by the long noisy backfiring limp home from Oregon and I haven't been able to get her back in the Winne. I'm going to have to be darned sure it's fixed.

[Rickf1985]

Guy's road trip! Hey, you got to check it out right?

[engineer bill]

Well, after a long absence, we're planning a short trip to Santa Cruz next week. Will cross my fingers and hope for a trouble free trip.

[engineer bill]

Hi Guys,


I'm back. Sorry to drop out there for a while. I had some health issues-much better now...


Replacing the (melted) spark plug wires seemed to fix the backfiring into the carb. up hills or accelerating hard. 
_______________________________________________


We took a couple of nice trips with no issues at all and then ran into another drivability problem. It's kinda weird-you guys are going to love it.  :)rotflmao


We make the trip from Martinez CA to Santa Cruz fairly often. It's about 150 miles. There's a good sized 5 mile uphill section about 50 miles into the trip (Mission Grade) and another about 100 miles in (Patchen Pass).


The Winne runs strong the first 50 miles of highway, strong up the first long grade and strong the next 50 miles. Then, 100 miles in, on the second grade, it starts backfiring (i.e. into the muffler), stumbling and missing. If I slow down to 20-30 mph it will settle down and get me there.


The same thing happens coming home. Strong for the first 100 miles including a big uphill and then starts misbehaving on the second big grade.


My mechanic checked it out and says everything looks fine. It runs great the next day. It idles smoothly, drives great on the street and highway and pulls strong up our local big hill on CA 4. The big problem going up that hill is to not get going too fast. But, put a 100 miles on it and it starts having problems on the hill: backfiring, belching, missing etc.


Clueless in Martinez...

[Rickf1985]

Sounds like an ignition problem from the backfiring description. It is getting gas into the cylinders but no spark and the gas is lighting of as it leaves the dead cylinder and hit the flame from other cylinders. This could be caused by a coil going bad or an ignition module going bad. Have you replaced the ignition module recently? And if you did did you put the recommended amount of thermal paste on the back of it? This could also be a burned plug wire showing up under high load and high heat. Definitely sounds heat related and electrical.

[engineer bill]

We replaced the ignition module today. Hopeful that it will do the trick.

[EldoradoBill]

The bushings in the distributors on these are notorious for short life-they get no oiling. Check for lateral play at the rotor (it first manifests itself as arcing in the cap). On the plus side you can buy a complete assembly including module and coil for around a hundred bucks.


Bill

[jeno]

I bought mine last year from jags it came complete with everything went in very easy extremely happy with it .

[engineer bill]

More on drivability problem...


This problem, (described below), only happens when the engine is good and hot-like after two hours of 60 mph highway driving. That's not to say overheated. Coolant temperature is less than 220 deg F.


After a period of highway driving, if I have to slow down, or stop (like at a stop sign), then when I start to accelerate back up to speed, (vacuum gauge drops into the "red" below about 8 or so), motor backfires a few times in the the exhaust manifold or muffler. If I'm starting off up a hill, like from an exit and underpass, it's worse. Then continous backfires until up to speed (vacuum gauge well up in the green.




Replaced plug wires and ignition module. No change.
My mechanic insists he can find nothing wrong with ignition. He's suggesting cracked exhaust manifold or bad gasket or jeez a bad exhaust valve.


Time for a new mechanic? I thought I had retired from the wrenching but maybe I will have to do it myself? Maybe time for a new hobby?


When I pick it up tomorrow, I'll check the distributor play.

[Rickf1985]

A cracked manifold will give backfires when you let off the gas not when you are on the gas. The only thing that will cause a backfire in the exhaust is excess fuel in the exhaust pipe and the only thing that will cause that, short of an extremely rich carburetor, is a misfire. A pretty consistent misfire at that. Now you also have to have air in the mix for it to light off but if your emissions equipment is still hooked up then there is your air supply. Somehow you are getting gas in the exhaust. Consider that in the past when you replaced the plug wires the problem went away, I know you don't want to hear it but check those wires good. If not the wires I would suspect a coil since it happens after a hard pull.

[engineer bill]

Thanks Rick. I just passed that all on to the mechanic working on the beast right now.


In the past, they've been really, really, good but I think they may be losing interest...