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Old 09-13-2014, 04:47 PM   #15
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Originally Posted by Skip426 View Post
The factory never installed an electric pump in these units, and if it's controlled by a switch on the dash , it's a definite , add on; probably to attempt to fix the issue you're having.
Do the air cleaner housing snorkels , have duct work that extends over the top of the rad to pick up cool air from behind the grill? ( in front of the rad.)
That may have be a mid 80's factory addition to try and deal with the after boil issue, that continued till throttle body fuel injection was introduced.
Interesting you should ask. No it doesn't. Just a standard 440 carb cover. No snorkels are attached to the intake. I think I am going to pick up a snorkel kit and give this a whirl. That's what I was afraid of. The motor isn't getting enough air, so the gas boils when the engine is turned off while it's hot. And when it's cold, so insufficient airflow to the carburetor sounds like the problem.

Thank you. You might have saved the day.
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Old 09-13-2014, 04:47 PM   #16
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I can't remember how I solved the problem it has been many years sorry


Joe 1998 Itasca Sunflyer Ford 460
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Old 09-13-2014, 04:53 PM   #17
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Might check that the fuel line that comes out of the fuel pump and goes to the carburetor is not close to any thing that is a big heat producer.
Yes I am going to put a high temp foam installation around the gas lines just in case the gas lines are having some hot spots.
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Old 09-13-2014, 04:56 PM   #18
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Originally Posted by cimplexsound View Post
The motor runs even if the electric pump is off. And I can hear the motor to electric pump when I flip the switch. So yes both are working. But I will give it a fuel pressure test to see if maybe one of the pumps are under performing or if I have a vacuum leak.
If the electric is an old Stewart Warner it may have a filter inside....not sure of that but seems like 40 years ago I kinda remember one.
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Old 09-13-2014, 05:02 PM   #19
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Thank you everyone for your help. I think it will be much easier to solve this problem than I had originally thanks.
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Old 09-13-2014, 05:06 PM   #20
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Something else to check on the electric pump, sometimes they will run continuously and overheat as well, or possibly overheat your fuel. As I recall they should shut off at a set pressure.


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Old 09-13-2014, 05:07 PM   #21
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Yes the choke is working. I pulled the dog house off while the motor was at operating temperature. The choke was wide open.
FWIW - My question would not be if it opens, that would be a running problem. For a starting problem the question is if it closes when cold. ;-)
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Old 09-13-2014, 05:55 PM   #22
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That electric fuel pump may have some restriction or is causing the engine driven fuel pump to work a little harder to get a sufficient supply of fuel to the carb, as in an example of what Ken is saying. In my experience with hot fuel issues, I've always had success in resolving the problem by providing a cooler fuel environment.

The way you do this is either by more fuel in the fuel lines, (larger fuel lines), or higher fuel pressure, (adding an aux fuel pump). Cooling the carb by using a spacer will work wonders. These are all modifications and are for the most part, experimental.

So lets get to the real cause of your problem first.

Your intake manifold has a heat cross over in the center.

The purpose of the heat cross over is to heat your carb, assisting in fuel burn quality, and a little to prevent carb ice.

The source of this heat is, the exhaust system being routed through you factory intake manifold.

Two choices I'll mention here and the first is to remove and clean your factory intake manifold, then replace the intake manifold to head gasket set with the newer metal type.

Some of the new gasket sets will have an optional cross over blocker. If you use this blocker, your fuel boil off issues will be resolved. Reinstall your factory manifold.

The restrictions to the exhaust flow through your intake manifold have burned completely through, this is allowing your intake manifold to over heat and boil off your fuel, and this is also causing your engine to run with a bad mixture. In time, after you have replaced the intake manifold gaskets, this issue will reappear. I'm not saying that will happen during the time period you own the vehicle.

You noticed I mentioned (factory manifold)? This leads to another fix to your problem, and this is a permanent fix and upgrade in one. That upgrade is by replacing your factory intake manifold, with a high performance manifold. Most high performance manifolds have that exhaust cross over blocked by it's casting, and the aluminum manifolds insulate the carb from excessive heat by design. Other benefits will be realized, but I'll leave that to you and your personal research.

I don't think you have an air supply problem at all, you would know that already as it should have shown up as a overly rich mixture, causing black smoke and bad gas millage.

If you follow the suggestion I've just outlined, I'm sure of this issue being resolved permanently.

DTW
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Old 09-15-2014, 07:33 AM   #23
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running

convert over to fuel injection.
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Old 09-15-2014, 06:40 PM   #24
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I'm afraid that would be way too expensive. Fuel injection requires a ECM. Car computer and fuel injectors cost about $300.00 each. I'd be running about $3500.00 before I'm finished. No need to keep this rig road ready since I'm leaving for Arizona in 2 1/2 months. Thanks you though.
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Old 09-15-2014, 06:48 PM   #25
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To DTW: yes I am in the process of putting high temp insulating foam around the fuel lines. This has an aluminum lining on the outside to shield fuel lines from high heat. About ready to install an air intake snorkel on the carb intake. It seems to be suffering for air, so I think the easier it is for air to get to the carb, I can expect better engine performance.
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Old 09-15-2014, 07:06 PM   #26
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I took the RV to my mechanic. No problems with the exhaust. It passed emissions/smog test without any problems. The engine and tranny run really good too. Heat is defiantly an issue. So again I'm starting by insulating the fuel lines first, and I'll report back to see if this helps.
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Old 09-17-2014, 03:47 PM   #27
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This may sound really silly, but try running it without the gas cap on. Someone replaced my gas cap with a locking one that was NOT a venting cap. I had similar issues. Bad vapor lock that drove me nuts trying to trace it. Pre fuel injection engines generally have lower fuel pressure, they can't have a sealed system like the new ones. I put a venting cap on and she starts and runs way better

Just a thought and easy check

Walter
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Old 09-17-2014, 04:01 PM   #28
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Cimplex,

Still wishing you the best of luck with that issue, however I think you misunderstood the information I posted.

I didn't mean you had an exhaust system problem, I'm saying you have an intake manifold over heating issue caused by the a reoccurring problem that is inherent with all these older engines, Chevy, Mopar, and Fords.

You've stated you won't be keeping this coach for more than another year. Therefore I would suggest you talk to your mechanic about replacing you intake manifold gaskets, and add a spacer under your carburetor. The addition of the fuel line insulation will also be very beneficial.

Ask him ( your mechanic) of the possibility of the exhaust cross over, that permits hot exhaust gases to heat the intake manifold over doing it due to deteriorated gaskets. He has eyes on you motor, as I'm suggesting this as a possibility site unseen by me.

I'm suggesting this as I have personal experience especially with GM engines in some of my passed projects. This will also give you a false indication of an engine staving of air. This is due to the fuel being boiled in your carburetor as you are driving. This ruins the mixture ratio.

Hope that clears that up for you. Please keep us posted.....

DTW
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