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Old 05-03-2013, 06:10 PM   #1
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Question Diagnosis help

I have a '99 4.0L wrangler. 95% of the time I have no problems with it, however three times since December I have gone out to my jeep and it wouldn't start. It cranks but will not start. Each time I have gotten it towed to the dealership, and when it gets there it starts right up. They have tried troubleshooting it but because it is no longer acting up they said they couldn't pinpoint what was wrong. I think it has a fuel issue just not sure how to tell if its the pump, an electrical issue getting power to the pump, or possibly a clog? Any ideas or insight? Thanks!

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Old 05-03-2013, 06:25 PM   #2
Knows a couple things...

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Does it ever stall while driving it?

The next time it won't start, try this... cycle the ignition switch on-off-on (not to the Start position) 5-6 times in a row to give the fuel pump plenty of time to get fuel up to the fuel rail next to the fuel injectors. If it starts right up, odds are very good your problem is from a leaky valve inside the fuel pump/fuel pressure regulator.

If that doesn't help, I'd be suspicious of the CKP sensor which is the Crankshaft Position Sensor which is mounted on the transmission/driver's side next to the flywheel. The CPS is what generates the engine's master timing signal & if it doesn't, the engine won't start. Which is why I also asked if the engine has ever stalled which is another symptom of a bad CPS.

If it has never stalled, I'm thinking more fuel pump/fuel pressure regulator assembly which is mounted on the gas tank.
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