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Old 12-01-2011, 11:32 PM   #1
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Default 1999 bonneville, 3.8, fuel pump circuit problems


I.m somewhat familiar with checking out engine electrical systems but I may be using the wrong fuel pump wiring info. here'* a summary and the background of the problem.

99 bonneville, 3.8, starts and dies, fuel pump relay operates before and during immediate start up, pressure at Schrader valve, Removed relay, jumped the pump feed and supply recepticals, engine starts and runs well. OK, the system that runs pump after start up is flawed.

I used the only available wiring diagram, it for a 1998 bonneville, ( maybe not a good idea,) I saw that an oil pressure sensor bypassed the relay,cool, made sense, it'* the wiring to the sensor or the sensor. I never just throw parts at a problem, but I stupidly put a sensor in without electrically checking the wiring or connections. The engine did run for 8 minutes
and died. I thought I inadvertantly caused a bad connection to temporarily make contact. That'* as far as I've gone so far.

But now I am looking at a 1999 diagram which does NOT show a oil pressure bypass circuit. Was I barking up the wrong tree? Does The PCM keep the relay actuated after start up via a crank sensor signal??

I would appreciate any info you may have regarding diagnoses of this problem

Thank You Peter
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Old 12-02-2011, 09:10 AM   #2

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I've never looked into the 99H body. However the W body stuff only sets a light when you reach 5psi of pressure. Which we all know is bearing killing area.

When you say you jumped it. Was that at the relay location or at the connector to the fuel pump? If it was at the relay, then you are likely losing the hand off from the ICM to the PCM. This happens via a signal from the crank sensor to the icm and after x seconds of running..it hands off to the pcm.

Let'* switch gears slightly
Kinda sounds like you are getting a prime that allows you to star the car. Once that prime runs out..you stall. So one quick question is..what'* the security ligh doing? If you trip security in a 97, it'll prime, start and run til that burns off. But it won't fire the injectors any further. So the question is.. do you have fuel pressure and no injectors or do you have no fuel pressure and no injectors.

Sounds like you have no fuel pressure, which is why I mention the security second. Just in case you do have pressure. However you tested for it already.
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Old 01-10-2013, 05:40 PM   #3
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Default Starts and dies

I had a similar problem. It will start and run for a while but died after a while or while stopped at a traffic Light. It was the mass air flow sensor. It was simple, like sliding a card on a compartment around the top of the engine, I don't quite remember. It was three years ago. Around $100.00
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