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1990 Jeep Cherokee Question: no power to fuel pump pigtail connector next to gas tank



Alvis Sachen, 4.0L 6 Cylinder, Fort Worth, TX, December 27, 2010, 13:37

Parked car for 3 months,then wanted to move it..it would not
start..turned over very healthy with new battery..will start
and runned fine with starting fluid.
-fuses ok,new battery,full voltage at relays block
-installed new pump relay,have full voltage in and out of it
-fuel pump has less than 1000 miles (replaced past summer)
-no mechanical malfunction or unusual noises present
**only "anything" fuel-related issue is a fuel gauge not
working (I left the key ON all day a year ago,gauge will not respond after that, but I was still able to drive car for several months).....I suspect an open ground circuit to
pump wiring or some kind of a trigger signal from PCM...
..As to the gauge,I am leaning towards the sending unit...
please advice....thanks!..

1 Answer
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  • Answer #1

    December 28, 2010, 15:53

    When the PCM receives a signal from the Crankshaft Position Sensor it grounds the Fuel Pump relay, which in turn powers up the Fuel Pump.If there is no Crank signal, the relay will not energize. As for your gauge, it is likely the sending unit.

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  • Reply

    Visitor, January 31, 2011, 12:28

    is it the crankshaft position sensor whats bad.

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    Alvis Sachen, January 31, 2011, 22:33

    thanks for your input..now..where is this sensor located?...how do I test it...resistance?..voltage?
    n.o. condition..n.c. condition?...can I override it so to make sure this is in fact the perpetrator?
    please advice

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