Mechanics

STARTS/DIES. +SECURITY LIGHT

1998 GMC Sierra

Computer problem
1998 GMC Sierra V8 Four Wheel Drive Automatic 200000 miles

Intermittent problem: starts and immediately dies. When this occurs, engune can be made to start and runs as long as I add fuel through air intake at crankcase ventilation breather tube. Sometimes, problem will resolve itself after doing this for a coulpe of minutes, but at other times it doesn't help- truck dies as soon as I stop adding fuel. New Fuel filters, new Injection spider system complete and new fuel pump/gauge sender module no help.

In my past experience chasing this problem I do not recall the problem clearing up in 10 minutes, or 30 minutes. Problem disappears overnight in most cases, although it has occasionally lasted for several days.

I have been chasing this for 1-1/2 years to no avail, except to pay 3 mechanics to NOT find the problem.

Updated Engine computer (Flashed the PROM) 6 days ago. No Start condition hasn't occured YET since update, bit I'm not expecting the problem to have been cured by this.

Was just made aware of a " Passlock 2" security system that could be the culprit, but unaware of how to properly troubleshoot (or bypass as a troubleshooting method) when problem occurs. I now recall seeing " Security" illuminated on the instrument panel while driving at odd times in past months, but have not related this to the " No Start" condition. Need to wait for next failure and leave key on to see if " Security" goes off.

Only other trouble was a failing O2 sensor wreaking havoc on the computer. Although it would start, it was making truck run horribly on/off. Would generate random multiple misfire, codes for 2 other O2 sensors instead of itself. I found it by disconnecting one at a time, and problem went away. Now computer correctly indicates this O2 sensor has no output. I don't THINK this is related to the " No Start" condition?
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Garwoodv6
June 20, 2010.




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