I’ve an RV built on a 78 Dodge frame with a 360 V8 I believe. It has a Carter ThermoQuad. It sat for two years and wouldn’t start. Replaced the fuel pump. Barely made it to mechanic. He replaced the filter, checked the timing and said the carburetor was all gunked up. Sent the caraburetor off to have it rebuilt. Ran a little better but only barely. Had to feather the gas pedal to keep it from stalling and it ran real rough once going. Mechanic said there was still something wrong with the carburetor. I sent the carburetor back. They put it on their engine and said it worked great and sent it back to me. Same problem. Drove it to another mechanic who has had a lot of experience with this carburetor. He could only get it to run good if he choked it manually while driving. Said there was something wrong internally. Sent it back again. They said it ran great but they made some minor adjustments. I’m about to reinstall it but am not hopeful and I’m curious if anyone has any ideas other than the carburetor that could be causing this problem.
I would suspect contaminated fuel since the RV sat for 2 years and the carburetor functioned normally on another engine. I’m surprised that 2 “mechanics” did not suspect this.
You might find some useful information here, @wildeted.
After reading all that …I never saw any mention of anyone completely removing the old fermented and rotted gasoline.
Did anyone think of that ?
Two year old gas ( or older depending on the last fill up time ) will not run much of anything.
Old gas has been an issue for me before and I put in Staybil in my 79 Chevy pickup which gets a fill up once every two years at best.
It runs just fine now every spring when I fire it up.
Definitely a good idea to remove all theold gasoline, then replace the fuel filter. Assuming you’ve done a fuel pump volume test and that is ok. Beyond all that, I suspect the problem is you’ve got a vacuum leak somewhere. Ask your mechanic to check each and every vacuum hose for leaks, especially look for breaks in the hoses right where they meet up with a vacuum connector. Then you have to check each and every vacuum operated device, one by one, for leaks in their diaphragms. On my Ford truck there’s a vacuum operated gadget in the air cleaner that is supposed to open and close depending on the temperature, and when the diaphragm in that device springs a leak, the engine runs and idles poorly. The leak allows unmetered air into the engine, causing a lean condition. Replacing that device (or just plugging that tube) immediately returns the engine to perfect idle.
The OP indicated that the engine ran with the choke partially closed which seemed to indicate a vacuum leak. The older thread that was linked was also an old Dodge can and the problem was leaking gaskets.
I used to have a '71 Plymouth Satellite and the vehicle stumbled under power at times. These may seem obvious, but bear with me. I did not find out part of the problem until the 1990s.
I have a couple of suggestions:
- Drain & Replace the fuel & fuel filter.
- Check all of your vacuum hoses and replace as necessary (or just replace them for the Hell of it because they’re old.
- There may be at least one heat passage from one side of the intake manifold to the other. Sometimes this gets carboned up and needs to be cleaned out. Remove the intake manifold, locate the heat passage and run a wire coat hanger through it. That should help. (I discovered this in the '90s long after the car had been sold.)
Have you checked the fuel pressure at the carb when running? As others have said, something is likely clogged up or not working. New gas is the first order of business.