no spark still... help please

[Sully]

pcm reflashed, and then didnt pull up any codes, but didnt start either. Im not convinced that the pcm isnt pooched

 

[Sully]

I can find tests for the cam position sensor harness... but not the sensor itself. Anyone have one?

 

[barebones 1500]

i got it just give me a minute to type it verbatim.

 

[Sully]

thanks!

 

[barebones 1500]

NOTE: test will throw a code and SES light will come on

1. reconnect plug to the sensor and use a probe on the brown/white wire terminal. connect the pos lead to the voltmeter and the neg to a ground. set meter to ac volts, crank the engine and the meter should indicate around 5.0 volts ac with the engine cranking.

that should be it. that is what is says in the Haynes manual.

 

[Sully]

so i need to shove a probe between ground and the brow/white wire while cranking? This should be interesting.

 

[barebones 1500]

Maybe you could get the wifey in the engine bay of your truck...jk

 

[Sully]

i think Im going to make some jumpers

 

[Aloicious]

here is the schematic for the spark system (technically its for a '96 but your 97 should be exactally the same), it might help a little:
http://www.gmtruckcentral.com/wiringdiagrams/1996/engine%20controls%205.0-5.7-7.4/1996%205.0,%205.7,%207.4%20CMP,%20CKP,%20ICM,%20and%20coil.pdf

you mentioned a new engine. do you have a thread about that? what are the specs/setup? what is the background on the problem (like when/where did it start happening)?

you don't have an oscilloscope do you?

IMO I think its unlikely that the PCM is actually bad. not to say that its not a possibility, but it would be WAY down on my list of suspects.

 

[Sully]

the engine was swapped in nov/dec time frame. I took a junkyard vortec 350 from a 98 and freshened it up. I replaced (with new) all the bearings, oil pump, gaskets, seals, the timing chain, distributor, plugs and wires, fuel injectors, and egr valve. I also swapped the emission stuff over from the 97 motor I was pulling out. They werent quite the same on the 98 so I put the 97 stuff on for plug and play reasons.

Lately the truck would spudder, and stall then not start. Then ater sitting for a while (sometimes days) it would just fire back up. I had originally figured it was bad fuel. Wednesday it died on the road and would start back up no matter what I did. After discovering I had no spark, I bought a new coil. The truck started and ran for 5-10 minutes then died suddenly while idling in park. It hasnt started since. I have since done everything mentioned in this thread. Everything in my ignition system is now new (since the motor swap) and I'm still getting no spark.