Stalls While Driving

To OP: Did you figure this out yet?

Your fuel tank is vented through a charcoal canister. The tank should run at a fairly neutral pressure (ambient) and is vented for both vacuum and pressure through the charcoal canister and sometimes the fuel fill cap. If the vacuum vent(s) is/are plugged, the fuel tank will develop a partial vacuum as you burn off fuel. The fuel pump will cavitate and fail to pump if the pump inlet is under too much vacuum. (less than ambient atmospheric pressure) You mentioned in your OP that it runs fine after you vent the tank by removing the fuel cap. Try confirming that the fuel tank vents properly before throwing parts at it. It is an older vehicle, but, 62,000 miles isn't much for a fuel pump (with good maintenance) in that era.

Chum lee

Krusty wrote:
91 E-350 would have port type injection system that ran 30-45 psi fuel pressure. 99.9% chance it is a weak fuel pump causing your issue. Very common on those, especially in hot weather. Replace your fuel pump and the inline filter too. I'm sure it will solve your problem.

x2

I had a 1989 E350 years ago that was fuel injected and had similar issues. It started with, while driving in hot weather, I would get a very strong gasoline smell. It was so strong that you were sure there was a lot of leaking fuel. I would stop and check everything and not find. any leaking gas! But when I unscrewed the gas cap, I got a loud whoosh of presure coming out of the filler neck. After that and not again until I would be driving in hot weather would it occur. Eventually things started getting really hot under the vehicle the propane tank pressure relief valve would shoot off a loud burst of gas for about 30 seconds and then eventually things would cool off and be okay. On this same trip, the ac condensing line came loose and shot all of the freon out. eventually the engine started acting up and I lost some power so that I could only go. 45 mph.

It turns out that one of the problems was the catalytic which had come apart and was partially plugged up which was causing the converter to overheat and run red hot.

I was told by a Ford mechanic that the 2 oxygen sensors were faulty and causing the failure of the catalytic converter which caused things around the vicinity to also overheat and fail.

Before you replace the fuel pump. hook up a fuel pressure gauge and see what the fuel pressure does when it stalls. If it's staying at 45PSI, the pump isn't your problem.

91 E-350 would have port type injection system that ran 30-45 psi fuel pressure. 99.9% chance it is a weak fuel pump causing your issue. Very common on those, especially in hot weather. Replace your fuel pump and the inline filter too. I'm sure it will solve your problem.

While it can happen it certainly isn't a normal thing especially these days in fact it is virtually unheard of in todays modern injected vehicles but remember this is a 30 year old injection system on a rv no less that probably lagged behind the rest of the auto industry technology to begin with, it is probably nothing more than throttle body injection which was in its heyday at that time period and those ran on about 9psi or so unlike todays that are running 40-60psi.

I know this is apples to bananas but my 01 diesel fuel injection pressure was 4-5k no rail now they are pushing 27+K rail pressure. Injectors and injector technology have come a very long way since 1991.

Good luck OP and congrats on your RV. Tell us how you fixed it and GoRV!

Thank you all for the great advice! Incredibly helpful! Scottiemom... you gave me hope! Yay!!!!

Thanks again! I will post updates after some repairs.

In gratitude,

@JoeSilvaWrites

Before throwing parts at it, some basic troubleshooting is in order. If you are able to duplicate the problem (often the hardest part), when it stalls carefully give it a brief shot of starting fluid into the intake to see if it starts or pops. Some will say you should never use starting fluid on a fuel injected engine, but a very brief shot for diagnostic purposes should not be harmful. If there's still no action, it's likely an ignition problem.

BarryG20 wrote:
Fuel injected engines can still experience vapor lock but it is much less prevalent than on carbureted vehicles.

Never heard of this ! Typical fuel pressure on an inject engine is 3 or 4 times that of a old fashioned mechanical pump.