1999 Jeep Grand Cherokee Logo

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Anonymous Posted on Oct 22, 2009

1999 Jeep Grand Cherokee Larado wont start. Cranks, but injectors do not pulse( fuel rail has pressure.)

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  • Anonymous Oct 23, 2009

    Not yet, but I will tomorow am. I can get it to hit on either. Does the cpm also control ignition? Also, the auto shut down relay buzzes witht the key on. I swapped it with another relay and it does the same thing.

  • Anonymous Oct 23, 2009

    Messed with the relay today, it seems that the ground is controled by the key, and that power is supplied all of the time to the other 2 sides. I am getting 9 volts between the magnetic side of the relay, but 12 volts from the hot 2 sides directly to the battery - post. How is the ground triggered in this circuit?

  • Anonymous May 11, 2010

    Test the crank position sensor?

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  • Jeep Master 6,982 Answers
  • Posted on Oct 23, 2009
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If computer sees no crank sensor signal it shuts down pulses to the injectors. But, you bring something new into the mix. Make sure fender grounding is good so the relay can operate properly and make sure power going to it is not restricted by a loose or dirty contact on the power side.

Testimonial: "Sounds like a good start"

  • Anonymous Oct 24, 2009

    You sound like you are at the point where you need this: http://www.scribd.com/doc/18999822/Jeep-... Try going here for a wiring diagram. it's better than hanynes or chilton, and I've used it often. I believe the crank sensor triggers the computer and the relays. Look through the diagram and you will get an idea how the wiring is routed.

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  • Posted on Jan 15, 2022
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Immobilizer (Security System, at least on my 1994 Grand Cherokee) disables engine by "zeroing" out pulse injector width. I'm going through it now. Runs with starter fluid, however, eliminating Crankshaft and/or ASD deactivation related issues. Have injector pulse while cranking, but loses it once it starts (and immediately dies). Camshaft Position Sensor, however, which is supposed to fluctuate between zero and 5 volts only fluctuates from zero to 3.8, which may possibly be enough to avoid ASD deactivation while causing injector pulse issues. Sheer speculaltion, however

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1999 Jeep Grand Cherokee cranks fine but won't start, has spark, no fuel pressure on the fuel rail, full tank of gas.

Fuel pump failure. Have someone open your gas cap an listen closely while you try to start the car. Your listening for a buzzing noises, if no noise pump has failed, very weak noise not enough pumping pressure to start the car. All 'n All "FUEL PUMP FAILURE"
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To fuel pump or not to fuel pump

if over 100,000 miles miles common.
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