1993 GMC Seirra Z71 4X4

1993 GMC SIERRA
V8 • 4WD • AUTOMATIC
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AALATA01
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my truck will not run even though fuel is reaching the injection unit, fuel pump relay has been changed, fuel pressure regualtor been changed, the fuel injectors do have power to them, and the fuel system puts out 14 psi., it will fire when gas or ether is manually injected into the t.b.i. unit, but will stop immediately. It also has been scanned but is not giving any trouble codes, the number one spark plug does have spark, what else is going wrong that will not let it run?
Mar 27, 2011 at 9:21 PM
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CARADIODOC
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Sounds like the Engine Computer isn't firing the injectors. You can verify that by plugging an injector connector into a "noid light". That will flash when the injector is pulsed. If it doesn't flash, suspect the crankshaft position sensor. (I have to defer to my Chrysler experience here, but in that respect, GM and Chrysler do things similarly).
Mar 27, 2011 at 10:20 PM
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WRENCHTECH
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This one doesn't actually have a crank sensor. The pickup coil in the distributor performs that function. If that were bad, you would lose spark also so if it runs by priming it, you do have spark. Check all your fuses and make sure the check engine light is coming on for a bulb check when the key is turned on.
Mar 27, 2011 at 10:47 PM
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AALATA01
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We checked all te fuses under the dash and fuel pump relay fuse. Are there any other fuses we are over looking and where are they. Is there an ECM fuse? ANd if the computer is bad is there a way we can test it, or does the EPROM chip have something to do with it? What do you mean by "bulb check" my check engine light comes on when the key is on.
Mar 27, 2011 at 11:34 PM
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WRENCHTECH
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It's sounding like a bad computer but all the power and ground inputs to the ECM would have to be verified first.
Mar 27, 2011 at 11:49 PM
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AALATA01
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Everything seems intact in regards to inputs and grounds. The computer also has what I think is a EPROM chip. I noticed that on new computers that you can buy this blue chip is not included. Would the truck need it to run, or is it an optional power chip? The chip says AC Delco right on it, so it makes me think it's a stock part.
Mar 28, 2011 at 3:18 AM
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WRENCHTECH
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The Prom is the personalization for your particular vehicle and that has to be transferred from the old one to the new one.I have to say that you could not have checked this out thoroughly enough yet. You need to verify every input and output of the PCM systematically.

Here is the pinout to do that.

This is with the 4L60E trans


Mar 28, 2011 at 12:51 PM
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WRENCHTECH
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That didn't work out as planned. I'll try it a different way.

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Mar 28, 2011 at 1:05 PM