1994 GMC Sierra

1994 GMC SIERRA
349,000 MILES • V8 • 4WD • AUTOMATIC
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BURLEY
  • MEMBER
  • 1 POST
my truck started to stall but would restart no problem. but now it wont and one thing i noticed is that the service engine soon light is not working, but every now and then it will come on with the key, and when it does come on the engine will start but it doesnt run for long.ive changed the pcm and no difference,oh and when the light isnt on the fuel pump wont come on either,ive checked the pump and it is fine,it seems like i have abroken wire somewhere but i cant find it
Nov 13, 2009 at 10:15 PM
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JDL
  • ✓Experienced Mechanic
  • 16,098 POSTS
Welcome to the forum. When the problem occurs, check ecm-ign fuse 10 amp, if you haven't already. Use a testlite, the fuse circuit goes hot when you turn on the key. Once you crank it enough to bring up oil pressure, the pump should run, there shows to be an o/p switch in the fuel pump circuit. If the switch and circuit are functional, all you need is voltage, to run the pump.

I wanted to add, voltage to the oil pressure switch comes from a fusible link, hot all the time. The pcm also gets voltage from the same fusible link.
Nov 14, 2009 at 1:30 AM
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