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Chris
Chris, Shop Foreman
Category: Dodge
Satisfied Customers: 9996
Experience:  ASE and Chrysler Certified Master Tech
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dodge 440 motor home: My 78 dodge 440 motor home seems fine

Resolved Question:

My 78 dodge 440 motor home seems fine when not under load. Starts fine and can rev the engine. Sounds good. Has headers. Has occasional backfire out exhaust. But under load it hesitates, misses, backfires and stalls. I can only lightly feather the gas to keep it going. It has all new ignition wires, coil, distributor cap, rotor, ballast, mufflers and exhaust pipes, fuel pump, and a newly rebuilt Carter Thermoquad. Could it be the ECU? It is driving me nuts.
Submitted: 1 year ago.
Category: Dodge
Expert:  Chris replied 1 year ago.

Welcome and thank you for allowing me to assist you! This sounds to me like a fuel delivery problem. You did not mention replacing the fuel filter in your question. Did you replace it?

 

 

 

Chris

Customer: replied 1 year ago.
I had bad gas in the RV and had it removed and replaced. I am assuming they also replaced the fuel filter.
Expert:  Chris replied 1 year ago.

Ok Cass, just be sure they did because a plugged up fuel filter will cause the exact same issue you are experiencing. If they did replace the fuel filter, then you may still have a plugged up fuel pick up screen inside of the tank, or a plugged vent in the gas cap. I think that something is preventing enough fuel volume from getting to the fuel pump and carburetor. One way to check for adequate fuel flow is to remove the supply line from the tank at the pump. Fuel should easily flow out of the disconnected line. If it does not, then suspect a plugged fuel filter, plugged screen in the tank, or a tank venting problem.

 

 

I hope this information helps, and let me know if you need further assistance with this.

 

 

 

Chris

Customer: replied 1 year ago.
Fuel flow seems fine as when I rev the engine when it is in neutral it revs up fine. There is no vent on the fuel cap. Would your solution still apply?
Customer: replied 1 year ago.
Relist: Other.
Answer seems wrong as I get 7.5lbs fuel pressure at the carb. Gas flow seems adequate. Chris is taking too long to reply after offering this suggestion and getting my reply. I had bad gas, it was drained and replaced and the fuel filter replaced. The engine revs fine in neutral and the problem is only when the engine is in gear and under load heading down the road.
Expert:  Chris replied 1 year ago.

Sorry Cass I had to step away from my computer for a bit. I see that you have 7.5 lbs of fuel pressure at the carb. Can you leave your test gauge tee'd into the fuel line at the carb and then drive the motor home and watch the pressure when it starts to act up? If it holds at 7.5 lbs, then I will be satisfied with fuel delivery to the carb. If it drops off, then my theory of a fuel delivery still stands. If it is not a fuel delivery issue, then it would have to be a weak spark or maybe a plugged exhaust problem. Try to check the fuel pressure while driving and let me know,

 

Chris

Customer: replied 1 year ago.
I don't see how it can be a weak spark as all the ignition parts are new. It can't be a plugged exhaust as the mufflers and tail pipes are new and it has headers. I'll try driving with the fuel gauge attached and see what happens tomorrow. I will leave this page open so I can reply if you respond now and leave me an opening to do so. Could a weak spark only under load come from the ECU being defective? Don't forget, it revs up fine when it is in neutral. I just get a burp out the exhaust when I let off the gas quickly. Just sounds like headers acting normal to me.....
Expert:  Chris replied 1 year ago.
I agree with you regarding the weak spark theory and that is why I went for the fuel delivery problem initially.However I have seen weak spark mimic a fuel starvation symptom. I don't think if it is a spark problem that the ECU would be the cause because if it was it would act up in neutral under no load. Maybe low voltage at the coil though. Let me know how the fuel pressure test goes. I will look for you tomorrow.

Chris
Customer: replied 1 year ago.
OK, Thanks. It will probably be tomorrow night.
Expert:  Chris replied 1 year ago.
That's fine Cass. I will keep an eye out for your reply. Have a good evening,

Chris
Customer: replied 1 year ago.
Well, this is the best $31 I ever spent on a mechanic. You called it right. The numbskulls up here didn't change out the fuel filter. I did that first thing this morning and she ran like a charm. Thank you Chris.
Expert:  Chris replied 1 year ago.

That is awesome Cass! It just really sounded like a poor fuel flow issue and glad that it was only a fuel filter. By the way the "numbskull" reference is right on. I cannot believe that it was not replaced.

Glad I was able to help, and if you need future help, please look me up!

 

Chris

Chris, Shop Foreman
Category: Dodge
Satisfied Customers: 9996
Experience: ASE and Chrysler Certified Master Tech
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