1993 GMC C1500 1993 won't start, got fuel

SILVER93GMC

MEMBER
1993 GMC C1500
V8
2WD
AUTOMATIC
142,000 MILES

Yesterday in traffic my truck died, it slightly stumbled for the 1st three red lights after starting fine at work. The engine now turns over but will not start. FP pressure is 15psi, 11.94 volts at both fuel injectors, TPS good.5 volts closed & 4.5 at WOT, engine seems to have fire will start with starting fluid, disassembled fuel pressure regulator, no busted diaphram. What else could it be? What should I check next? Thanks

6 Replies

JDL

MECHANIC
16,098 POSTS

Welcome to the forum, can you see an injector spray pattern, engine cranking? Check injector plug for B+ and ground. Without rpm signal no injector pulse.

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Saturday, November 21st, 2009 AT 2:17 PM

SILVER93GMC

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No spray pattern..018 vdc on b+ (blu & gr) term & batt voltage on red and white. What should I see at the b+ term? What provides the RPM signal on the 93? Thanks for the info.

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Saturday, November 21st, 2009 AT 2:22 PM

JDL

MECHANIC
16,098 POSTS

The purple wire with white tracer, carries rpm signal from ignition module to computer, engine cranking. If no pulse on that circuit, I suspect the ignition module.

I just noticed the voltage readings you gave. The red and white, is B+ with key on. The other wire colors should be ground, no ground with the key on. Engine cranking, there should be a pulse on the ground wire. With key on, no crank, meaning no ground, there would be voltage on both circuits at one injector. If there is constant ground, that circuit may be shorted to ground, or faulty pcm. If I caused you extra work, my bad, sometimes I get in a hurry.

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Saturday, November 21st, 2009 AT 2:52 PM

SILVER93GMC

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I'll take it out, have it tested and let you know. Thanks.

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Saturday, November 21st, 2009 AT 2:58 PM

SILVER93GMC

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That was it. Makes all the sense in the world, I wonder why none of the books suggest this as a cause. Thanks again, saved me from changing a good fuel pump as suggested by all the guys that stopped by my house and said they had seen this a hundred times before.