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Fuel pump problem?

JBurian

NAXJA Forum User
Location
Moscow, PA
I think I'm having problems with my fuel pump ('94 Cherokee Sport 4.0L, 277,000 miles). It randomly dies while I am driving, still have all electronics, gauges, etc, then after I sit for a minute or so, it will start back up with no problem. It's been doing it more and more the last few days. Is there any quick (and easy) method for checking to see if the fuel pump is bad? Fuel filter was replaced about 8 months ago. Thanks.

Jeff
 
I don't think this is a fuel pump problem.

The #1 cause of thermal (heat related) failure on the 4.0 is the crankshaft position sensor.

The #2 cause is the ignition coil, but the crank sensor fails WAY more often.

You can test both of these components, but unfortunately for a thermal problem like this, testing would have to be done when the engine won't run and testing may not be conclusive.

If you end up buying a crank sensor, do yourself a big favor and buy it directly from Jeep for the best reliability and longevity. No lack of issues with aftermarket crank sensors.
 
Coil was replaced about 1 1/2 to 2 years ago, but will try to check it anyway. Was thinking of replaced CPS anyway, so I may just go ahead and try that also. Thanks for the quick response.

Jeff
 
Forgot to mention that this afternoon, it wouldn't start after sitting for a couple of hours. Cranked fine, but wouldn't start. Got out and banged on the underside of the fuel tank by the fuel pump. Started, but then died as I was driving out our lane (1/4 mile). Finally started again after sitting for about 10 minutes (tank banging did nothing second time).
 
You can certainly keep a fuel pressure gauge in the cab and check fuel pressure quickly when symptomatic. (should have 31 psi at idle).

But my hunch here is a crank sensor. They can become intermittent and subject to thermal failure when they are starting to croak.
 
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