1990 Chevy Truck Fuel System

  • 6 CYL
  • 2WD
  • 225,000 MILES
I got this old truck, cheap, as the tranny was bad and the owner knew it, and, it had been sittin' for two years. I've tinkered with it some before I pulled the tranny, and took it to a rebuild shop I know. After some intricate troubleshooting, I hadda replace the Ignition Electrical Switch, NOT the KEY switch. You know, the one on top of the steering column, below the dash? OK, a little tough, but do-able. THEN, when trying to start the truck, just to see if the tranny would move it at all, I wasn't getting any fuel at the TBI. With a prime, from a jug of gas, it would "bump-start" and idle for several seconds, without pedal manipulation. Listening, I could her nothing from the fuel pump with the key on. I've changed a fuel pump before, on my 93 Chvy 4wd P/U. Not too tough, at all. So, just recently, when I yanked the tranny out of this 90 model 2wd, I went ahead and changed the fuel pump in the tank. When done puttin the tranny back in, it wouldn't start without a prime. Listening, NO SOUND from the pump! OK, OhmMeter in hand, with the key on, I found NO voltage at neither ther FUEL PUMP RELAY, nor the FUEL PUMP RELAY FUSE that was right beside it on the firewall. OK, I jumped 12v to that fuse right from the batt to check the system, and I heard the pump start running. Still, won't start without a prime, and then dies. I loosened the line at the back of the TBI, and powered up the fuel pump. Gas ran out around the fitting almost instantly. Tightened it up and the pump never shut off. Then, it still needed priming. I can see that the injectors aren't shooting anything! OK, are the injectors and the fuel pump relay fuse on the same circuit? I appear to have a loss of voltage on both, and only these two items on the pickup. All the fuses seem to be good with an Ohmmeter. Didn't see one for fuel pump, but saw the INJ fuse, and it was good, 12v showing. How do I troubleshoot the power supply to the fuel pump relay fuse, where does it come from, and the same goes for my injectors, how do I check 'em to see if they work. And, does the "hotwire" I have to the pump, it just replaces one that is for some reason not present, but would that keep the pump from shuttin off when pressured up? It ran the whole time I worked at troubleshooting, never quit, till I unhooked the wire I jumped from the battery. Need help with this one, as I am no Wiring Whiz, lol. Thanks, Phil
Do you
have the same problem?
Wednesday, March 11th, 2009 AT 4:57 PM

1 Reply

You need to ck the fuseable links at the starter. They will be made of a special wire that is the actual fuse. DO NOT use a peice of wire to repair it but if you find one bad (try to stretch each one or test with a test light on the wire side)you can use a peice of wire for TESTING ONLY. It's very common to find one blown. Look for it to be shorted to exh. Manifold. Usually caused when changing starter.
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Thursday, March 12th, 2009 AT 8:17 AM

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