How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Chris Your Own Question
Chris, Shop Foreman
Category: Dodge
Satisfied Customers: 12586
Experience:  Dodge/Cummins and Chrysler Certified Master Tech
Type Your Dodge Question Here...
Chris is online now
A new question is answered every 9 seconds

dodge 440 motor home: My 78 dodge 440 motor home seems fine

This answer was rated:

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.

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?





Customer: replied 3 years ago.
I had bad gas in the RV and had it removed and replaced. I am assuming they also replaced the fuel filter.

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.





Customer: replied 3 years 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 3 years 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.

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,



Customer: replied 3 years 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.....
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.

Customer: replied 3 years ago.
OK, Thanks. It will probably be tomorrow night.
That's fine Cass. I will keep an eye out for your reply. Have a good evening,

Customer: replied 3 years 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.

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 and 6 other Dodge Specialists are ready to help you