Stalling out after long drive

[shimniok]

Yesterday on the trail the Jeep was stalling out, due to no fuel, about halfway thru Bunce School Road trail. It was pretty hot out and the Jeep was having trouble staying cool all day.

When I turned the key or started it, the TBI fuel pump wasn't running. I suspected bad connection and redid that. Fired up and we got thru the rest of the trail.

However, on the way home about 10 miles from home (South Suburban area) after 1.5 hours on the hwy at various speeds, the Jeep stalled out again.

This same thing happened in jun 2014, also on long drive back from Boulder, but at night. I thought it was fuel pump and swapped it but it did it again just before getting home. It never did it again after that until yesterday. Had zero problems on the way to and from Ouray and no issues on any trails there.

Since I was stalled on a narrow shoulder right at I25 offramp to I225, I didn't want to crawl under the rig. I let it sit several minutes. It started up, ran fine, and I made it the remaining 10 miles home.

So, any thoughts?

Only thing I can think of is fuel pump relay that sometimes dies when on for a long time or else a bad transistor driver in the TBI ECM.

What is strange is that it rare and inconsistent.

See, this is what I get for fixing up things on the Jeep lately. I've disturbed the conservation of dilapidation. Fix one thing, something else must break.

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[AwesomeJ10]

Well fuel pumps do go bad and they go intermittent first. I always carry a spare.

Other than that - vapor lock? It was hot yesterday....

I've had the sf512 chip get lose in the honcho causing it to cut ignition while driving....

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[COLORADOCRAWLER]

Throttle body getting hot? I've had the carb on my baby Jeep get hot on the trail. If the engine Temps were getting up there it's a possibility. It evaporated/boiled of the gas as soon as it entered the carb. Had to pour gas down the carb to prime it and cool it down. Started right up.

[FSJ Guy]

Does opening the fuel cap and venting the tank help any? Maybe the tank is building up vacuum and not allowing the pump to pull as much fuel?

What does your fuel pressure do when this happens? (Yes, I put a cheap gauge on my last Jeep just to monitor it for troubleshooting purposes)

[shimniok]

Thanks all. The weird thing is that yesterday, the fuel pump wasn't running when I tried to run it after it stalled. That is why I was messing with wiring.

I guess I will have to add some instrumentation for fuel pump power and fuel pressure for the next time this happens.

Not a lot of information to work with at this point, I know.

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[az chip]

I have a Isspro EV2 fuel pressure gauge for the TBI in my CJ7. 134.00 online. It is a sensor with wiring only in to the cab. Then I put a AN6 adapter on the input fuel line at the throttle body.

Fuel pump power monitor is an input in to the ECM. You have the 7747? Have not experienced that fault but if you lost pump power either because of wiring or the relay should that not turn on the CEL?

[AwesomeJ10]

you know... if you were still plagued with 'carb syndrome' , this discussion would be centered around the pickup sock/filter being clogged or vapor lock.

I doubt you are having any kind of TBI related issues, so my guess is it is a fueling issue and a simple gauge will determine that...

[FSJ Guy]

The OEM wiring had a second fuel pump power supply that ran through the oil pressure switch. The ECM of course powered the pump in the "key on" position, but once the engine was running, it ALSO powered it via a separate hot 12V that ran through a NO oil pressure switch that closed when oil pressure was above a certain amount. That said, I think you're on the right track to monitor fuel pump voltage. And Blake has a good point about the fuel sock and such.