1990 GMC Sierra Truck won't start

STEVENSHUMATE77

MEMBER
1990 GMC SIERRA
V8
4WD
AUTOMATIC
95,000 MILES

Problem started with truck stalling out while driving. Would not re-start unless I squirted gas in the throttle body. Sometimes it would stay running and I could turn it off and restart it with no problem other times it would only run until the gas I squirted in the TB was used up. I replaced the fuel filter, no change. Checked fuel pressure, around 10PSI. Took it to a shop and they diagnosed it a bad fuel pump. Had the fuel pump and sending unit replaced. Picked up the truck, drove it home (stopped for gas) and had no problems. About an hour later I went out to the truck and it would not start. It's like something is preventing the injectors from pulsing. Any suggestions?

2 Replies

DOCFIXIT

MECHANIC
18,828 POSTS

Hi
Need to determine what is lost spark or fuel. Pull plug wire hold next to block crank spark? Spray your stuff and see if it lights? Check engine light on?
Let me know
Thanks for donate

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Thursday, May 14th, 2009 AT 2:31 PM

STEVENSHUMATE77

MEMBER
2 POSTS

Truck is currently back in the shop so I can't say for sure what it is doing now, but before I took it to the shop the first time I could get the truck to start by priming the TB so I assume spark is/was good. I never did check spark when it wasn't starting. I can definitely hear the new pump (ACDelco) kick on when I turn the ignition on, but I did not check fuel pressure this time. Before I took it to the shop the first time I was getting a little over 10PSI when I put a gauge on it. When the shop tested it they said it dropped to 0, that is why it was replaced (also replaced the fuel sending unit at the same time). So, hypothetically, if fuel and spark are good, what would cause the truck to die while driving (no sputtering, just dies) and not restart unless the TB is primed? Even when priming, sometimes the motor would start and keep running or run until the gas I poured in was used up. My current list of possible culprits is: Ignition module, pickup coil, oil pressure switch, ECM, a short.
PS. No CEL, I did check for codes and the only code I had was 12.
Thanks for responding!