We have a 1986 28', Barth with Chevy 454 engine, 4 barrel carbrator. The engine backfires rapidly with any accelleration. With the backfire it losses power. Finally it comes to a stop. It will usually restart. This problem has persisted for four years. No repairman has been able to issolate the problme. In 04 a new carbrator was installed. It ran perfect for a few days. The unit was stored. Spring of 2005 it ran fine for 5 miles, started backfiring and came to a stop. The mechanic who installe the carbrator said he had never seen a butterfly bent so badly for backfiring. He replaced the carbrator again. It is doing the same thing. Any hints from anyone?

It sounds like timing to me. Start with plug wires, make sure they are on the right plugs. If this is not the problem make sure the distributor is timed right, the plug that it is pointing to is coming up for firing at the right point, just because the wires are on the cap in the right order doesn't mean they are aligned with the rotor.
If this shows no problems, you may need to replace the electronic module if you have one in the distributor. They can jump timing under acceleration if they are in "not entirely failure" mode.
If this has not solved the problem start with a compression test, it could be a valve or valve timing problem. If this doesn't show a problem, call Roy.
Tim

Backfiring on acceleration is a classic lean mixture symptom. I would install a fuel pressure gage first. Even a temporary lash up using a vacuum gage will do the job. Be sure the filter in the carb inlet is clean. When was the filter inside the right frame rail last changed? Does it do this with a completely full tank or close to empty or what? I don't know if your Barth has a fuel filter on the pickup in the tank, but those things can drive you crazy. I had a load of floating crud in my tank once that would clog the pickup filter just often enough to drive me crazy. My BArth has a big drain plug on the tank. Also consider using some Red Line fuel system cleaner. It has done wonders for me.

If it does this while you have good fuel pressure, consider a new coil. A weak coil will do this, too.

A stuck power piston will do this, too, but usually will not shut down the engine. Have you mechanic check the float level and the power piston. These can both be done without removing anything but the air cleaner.

Listen to bill h and check the simple stuff first. I had a similar problem to your's and expected the worse.

I had three problems contributing to the backfiring and power loss.

1. I had a bad alternator causing ignition interuption.
2. I changed out the fuel filters ($6 worth total) and discovered dirty water in the one closest to the fuel tanks.
3. I found a bad spark plug wire which was too close to a high-heat source.

Good point on the plug wire. A new set is always a good idea, and you will have spares. The current owner of my previous coach had a plug wire die in the mountains of Missouri, and stuck in a spare that I had left him and continued on his way. It was a Sunday and he was facing a big big tow charge.

Thank you Bill H.
I had made arrangements to take our 88, 33' SE (49,000 mi) in to the mechanic on Monday morning trying to track down some of the same kind of issues discussed in this post. The coach was running pretty good but occassionally would act up like mentiond here. I decided to take your advice and put in a large bottle of Red Line fuel system cleaner and put on a couple hundred miles on the weekend. With-in 100 miles I could tell the Barth was running like a new machine. All of the previous symptoms are gone and it runs beautifull. I greatly appreciate the advice and will recommend the Red Line to anyone who is having these kinds of issues.

Just had the carb rebuilt. Same backfire problem when I hit the gas.

I think fuel but have a new set of plug wires because they are easy to change and before the headers the old ones got burned. I will let you folks know what I find.

It appears to be the fuel filter, this is the extra one down by the tank. New filter and it works up and down the street. This weekend I'll drive it some more and post the results.

I still have no idea how to set the idel jets but one thing at a time.



[This message has been edited by timnlana (edited June 09, 2005).]

Never had a backfire problem, but it bogged down under heavy throttle, & threatened to die. New fuel filters cured it.

Steve, I am guessing many like myself are wondering what you found to be the problem?

Probably something simple, like me, SIMPLE. I love life, my family, and friends though.

Dale

Thank you everyone for offering your advice about our backfire loss of power issue. Apparently we have it fixed. We replaced the fuel filters (both) and plug wires. A rebuilt carbrator was installed as well. It has only been driven about 50 miles since the repairs in spring of 05, but it runs like new. Thank you all. Steve Austin, Red Gold, Inc. 765-754-7527 ex5. 1311. saustin@redgold.com

Glad it worked out Steve......

For those who may be contemplating having their 454 Q-J carb rebuilt and don't have a local reliable source, I'd highly recommend that you pack it off to: Auto Clinic, 722 M-139, Benton Harbor, MI 49022.

Oscar Heritz, the owner, has been rebuilding carbs full time since high school - he's a year or two from retirement now. He specializes in GM products. He's inventoried "cleaning products" that the EPA yanked off the market years ago, and your carb comes back looking better than the day it was originally manufactured.

I think I spent less than $20 shipping both ways....More than off-set by his small town labor rates......

He'll gladly answer any phone questions: call 269-927-2237 (If he sounds a tad grumpy, it's because he is, but it grows on you

quote:

Originally posted by bill h:
Backfiring on acceleration is a classic lean mixture symptom.\

Also, while you have the doghouse off the engine, replace as many vacuum lines as you can reach - a leaky one will do the same thing as low fuel pressure....

Does Redline do anything for diesel engines?