Dies after starting

Tiny
LAGRANGETONY
  • MEMBER
  • 1993 JEEP CHEROKEE
  • 6 CYL
  • 4WD
  • MANUAL
  • 10,000 MILES
Enter your question.93 cherokee laredo starts then dies after a couple seconds, checked filter, fuel pump runs then shuts off after key is turned, why is it doing this? Please help
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Thursday, March 24th, 2011 AT 5:25 PM

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Tiny
JDL
  • EXPERT
Maybe your losing rpm signal? Any applicable codes? You can check those codes, yourself. Initial prime, pump will run, AFTER that, if no rpm signal, it will shut off. May kill spark and injector pulse, also.
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Thursday, March 24th, 2011 AT 5:33 PM
Tiny
CARADIODOC
  • EXPERT
Hi guys. The fuel pump is supposed to run for one second after turning on the ignition switch, then it stops. That is what turns it off in a crash that ruptures the fuel line. Raw fuel would pump onto the ground and create a severe fire hazard. Engine can't run without fuel pressure. When it stalls, the Engine Computer sees the loss of pulses from the crankshaft position sensor and camshaft position sensor so it turns off the automatic shutdown (ASD) relay. That removes power to the ignition coil, injectors, a few other things, and the fuel pump or pump relay. That part is working normally, but you made an important additional observation. It runs for a few seconds. That means those sensors are working and it's in "theft" mode. The computer is turning off the injectors. Try unlocking the front doors with the key to turn the anti-theft system off. If your vehicle does not have the factory-installed anti-theft system, a computer glitch may have caused either the Body Computer or the Engine Computer to self-program itself into thinking that system is on the vehicle. It will teach that programming to the other computer and once upgraded to that programming, it can not be undone. You must replace both computers at the same time with new ones or with used ones that are both from vehicles without the anti-theft system. If you just replace one computer, it will learn the anti-theft programming from the other one as soon as you turn on the ignition switch.
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Thursday, March 24th, 2011 AT 8:24 PM

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