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1990 Jeep Cherokee 4.0 issue

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Along time ago this jeep was my first vehicle (14 years old just for driving around the neighborhood) I had issues keeping it running, electrical system must have suffered a failure at some point in time.

Sometimes it will pump fuel just time, other times, nothing, I have good fuel in it, and was gonna replace the fuel filter tonight, but when I turned the key with no fuel filter in, nothing, I have tested it this way before and have gotten fuel flow so its not a safety built in, any ideas? Ive been told possibly the computer, and by the numbers the one thats in it is not the original one (wrong number) but sometimes it works great and sometimes not at all. Last night it left me stranded, low electrical out put, i had a boost box, it would crank, start and then die instantly. same thing tonight with a fresh battery, except as of a couple moments ago it wont crank at all.

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I checked it this morning, perfect amp's

fuel filter is in it, it starts, runs for about 2 minutes, and dies, fuel pressure gauge reads zero???

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They had a lot of problems with the crank angle sensor, it's mounted in the bellhousing....just a possibility

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Yes, if the computer doesn't sense crankshaft revolutions it will shut down fuel and spark...something about cars catching fire in accidents and stuff like that.

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Did you try the fuel pump relay?

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I am 99% sure it is the CPS (crankshaft position sensor).

I have an 89 and had similar problems and so have many others.

Check out NAXJA.org. A lot of info and knowledgeable people. Only a few knuckleheads.

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plus one on the crankshaft position sensor the jeep 4.0 is notorious for having them fail. It will cause all sorts of fun issues to diag when one fails.

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