HELP no spark

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Schurkey

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It was in a red 1991 k1500 I swapped a vortec top end on it and did the timing cover for the crank position sensor.

My truck is a 96 k1500 and before I seaped in this 5.7 it was a 5.0 then was swapped to a 5.7 (last year not by me) and now another 5.7 vortec is going in
So you have a '96 that originally had a 5.0L then got a modified TBI short-block with Vortec top-end 5.7L, and is now getting a '96 [Edit: Should have said " '98 " ] Vortec 5.7L?

All these engines have the usual Vortec sensors and injectors?

Do you have power to the ignition coil and module? Does the computer show RPM when cranking?
 
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AuroraGirl

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So you have a '96 that originally had a 5.0L then got a modified TBI short-block with Vortec top-end 5.7L, and is now getting a '96 Vortec 5.7L?

All these engines have the usual Vortec sensors and injectors?

Do you have power to the ignition coil and module? Does the computer show RPM when cranking?
I feel like the 96 truck is gonna have a completely different PCM and control systems for things, so if its .. er.. wait.. it NOW has a 5.7 from 96?
 

Schurkey

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Whoops. I meant that it is now getting a '98 Vortec 5.7L. I mis-typed '"96".

Point is, it's had several engines, but they've all used the Vortec-style crank trigger and ignition system, and Vortec injection.

What's wrong is probably not due to the engine swap, but simply a fault somewhere in the normal Vortec systems--failed parts, pinched wire.

Whether a 5.0L computer can properly control a 5.7L engine is beyond my pay grade. But I don't think there's a problem with a '96 computer making sparks on a '98 engine. (GM didn't re-pin harnesses...right?)

If the scan tool shows RPM when cranking, the crank sensor and sensor harness are working. That leaves module, coil, ECM, harness from ECM to module, ignition switch/harness/power to module and coil.
 
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GMTMark

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Could it be VATS? Also the ‘98 and ‘96 have different ecm’s even though they are both black boxes. I don’t know the differences. HPTuners works well with my ‘98 but they don’t support either ‘96 or ‘97 (something like that).
 

AuroraGirl

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97 is, to my understanding, a pretty significant year milestone in most GM pcms, in park avenues its 1 year only and the last year to use an external knock module, the data rates and whole bunch of things are just wacky that year, 98 starts to see normalcy. but 97 was the first year of class 2 on those.

on trucks, i would suspect there may be some obd2 misfire, knocks, or just overall timing control stuff that would be different since 99 was the last year for light duty, light duty vehicles to be obd2 compliant. so even tho you got the connector and codes in 96, auto makers could have things like IM monitors and functions on the engines not compliant until 99. 04 was the cut off for >9600 gvw (Heavy duty light duty vehicles)

so frankly I think it needs a look into it for sure because that was a crazy time for electrical systems engineers lol
 

GavinJansma

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So you have a '96 that originally had a 5.0L then got a modified TBI short-block with Vortec top-end 5.7L, and is now getting a '96 [Edit: Should have said " '98 " ] Vortec 5.7L?

All these engines have the usual Vortec sensors and injectors?

Do you have power to the ignition coil and module? Does the computer show RPM when cranking?
I'm putting in the modified tbi 5.7 in right now already had a old 5.7 that dropped a rod bearing... yes it has everything vortec that I swapped over from the old vortec. I tested the coil with my multimeter and I'm not completely sure I did it right but it said it was ok and I also swapped the coil out with a different one as well and it didnt make a difference. Im not sure what you mean that the computer shows rom when cranking but I'm guessing you mean does the rpm gauge move while cranking, I never looked for that but I can look tomorrow.
 

GavinJansma

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So I think I confused everyone. The truck started as a 1996 5.0 vortec. Got litter knock drove till she died. Then put another 1996 5.0 in it work for 3 weeks they sent her a bit too hard pulling on the interstate. 3rd engine was a 1998 5.7 vortec drove for less than 50miles and it got a rod knock. 4th engine is a 1991 I believe bottom end with the old 1998 vortec thrown on it and everything was transferred over that I needed from the vortec. Kinda that Johnny cash song.
 

GavinJansma

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So I think I confused everyone. The truck started as a 1996 5.0 vortec. Got litter knock drove till she died. Then put another 1996 5.0 in it work for 3 weeks they sent her a bit too hard pulling on the interstate. 3rd engine was a 1998 5.7 vortec drove for less than 50miles and it got a rod knock. 4th engine is a 1991 I believe bottom end with the old 1998 vortec thrown on it and everything was transferred over that I needed from the vortec. Kinda that Johnny cash song.
But what I guess I'm trying to explain is that it ran perfectly with a 1998 5.7 I just swapped the 5.7 98 PCM in it so it ran good
 

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Im not sure what you mean that the computer shows rom when cranking but I'm guessing you mean does the rpm gauge move while cranking, I never looked for that but I can look tomorrow.
Better than nothing.

What I meant was for you to connect a scan tool, and verify that the computer sees an RPM signal from the crank sensor. From there, you can verify all the other sensors as needed, but of course you'd want to concentrate on the ignition system--cam sensor offset with the scan tool; ignition coil and module power using a test light or voltmeter. You should be able to verify that the module is at least partway working by looking at the dwell during cranking. If you have no dwell, you've got problems in the module, wire harness to the computer, the computer itself, or the signal from the crank sensor.

If you have dwell but no spark, you've got problems in the ignition coil, or the wire harness to the coil.
 
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