96 Vortec kicking my ass

[Scuby]

I got a 96 Vortec that I got with a no spark issue. How hard could it be right?

Guy b4 me had done the ecu, it ran 15 minutes then died. never fired since.

I've done:

New CKPS
Fixed broken wire to ICM
New ICM
New Coil
Verified ALL valves being operated AND that initial mechanical timing is dead on.

I get spark to the plugs. Cap and rotor aren't old. Pull a plug wire off and ground the plug I get spark so I "assume" the plugs should be too. Thing is. No matter what I give it down the throttle body it won't fire up. Not even a hickup. Just cranks. No signs of life.

This is a propane truck so I'm using brake clean to diagnose this issue as I've ruled fuel delivery out as an issue. Gasoline is disabled so disregard that as an option.

I got spark. I got signal from the PCM to the ICM. Coil is firing. Timing is on. Refuses to fire.

Please help me before I burn this thing to the ground.

What am I missing?

 

[skylark]

Compression.

 

[Hipster]

or a jumped timing chain

 

[Steve A]

Guy before you did the ECU? Replaced with a like unit or 0411 PCM mod?

 

[Scuby]

Guy before you did the ECU? Replaced with a like unit or 0411 PCM mod?

Like unit. after that PCM was installed it ran for 15 minutes perfectly then shut off as if key was turned off. Compression is fine. Should have mentioned that. Jumped timing is theoretically possible but I think unlikely. Especially as I today I double checked static timing and balancer sits dead on at mark on the crank while Cylinder 1 is at TDC on compression stroke...

Only thing I haven't done are cap and rotor and I ordered those today...

 

[Tom P]

My Apologies for not remembering the correct name of the part I'm trying to think of, but the P/O of my truck were chasing a similar issue before they sold it to me. I have the receipts from the shop showing they replaced a whole bunch of ignition parts. What the problem ended up being was some kind of a security control module. On the 96 and newer trucks, GM added a security module to control the ignition, which completes the circuit when the proper key is inserted. When the module dies it wont allow the truck to run, as if it was some kind of hotwire protection. I'm not sure if this is your issue and I'm sorry I have no clue how to test it or where its located.

 

[skylark]

My Apologies for not remembering the correct name of the part I'm trying to think of, but the P/O of my truck were chasing a similar issue before they sold it to me. I have the receipts from the shop showing they replaced a whole bunch of ignition parts. What the problem ended up being was some kind of a security control module. On the 96 and newer trucks, GM added a security module to control the ignition, which completes the circuit when the proper key is inserted. When the module dies it wont allow the truck to run, as if it was some kind of hotwire protection. I'm not sure if this is your issue and I'm sorry I have no clue how to test it or where its located.

Also, you make no mention of testing the fuel system. Perhaps make sure you are getting fuel. Could be that your fuel sender is toast.

They started the security in late 97.

 

[Tom P]

They started the security in late 97.

Thanks for the correction. I assumed it came with the updated interiors in 1996.

 

[skylark]

Thanks for the correction. I assumed it came with the updated interiors in 1996.

No worries. If you pull a newer gauge cluster out you will see something to the effect of "1998 truck" on the circuit board.

 

[Scuby]

That's VATS ajd your cluster will have a light thay says "security". It disavkes fuelingnafter a few seconds of running. Works with a resistor in the key. The passlock module looks for the right resistance and then provides the ecu with a signal that its good to keep fuelling the motor.

Good idea but not in mu truck indeed.



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