no spark! Im desperate

[scrapyardbound98]

So I see other no spark threads and I promise I have read them all. I am in desperate need of some help. This was supposed to be an easy distributor swap. 1998 C3500 5.7 Vortec. Original problem was that the truck would start, and grumble and backfire and stumble, but eventually would level out and be drivable. turn the truck off and it would happen all over again. Mechanic friend of my dad told me to change the distributor. I stupidly bought an amazon cheap set, wires, cap, rotor, plugs. Installed those and got no spark to the coil. Mechanic friend came out again, told me I had no live data from the ECU. Bought junkyard ECU, tripped passkey system. Truck would run and shut off as expected. I bought all new steering column sensors and defeated the passkey system, checks out as good on the scanner, truck ran for about 15 minutes and as the steering wheel was going in, the truck died. No spark to the coil again. So now all distributor related sensors are new (crank, cam, ignition control) and I bought ANOTHER distributor set up (Carquest premium, I'm running out of cash) still no spark to coil. Now the mechanic friend has me chasing wires in the main engine harness and I just have this itchy feeling that I am missing something here. He has me chasing the pink wire with the 'Fuse link' in it, and I honestly have no idea and I am losing customers because this is my service truck and I just can't keep chasing a ghost. PLEASE help me.

 

[scrapyardbound98]

Thought I would also throw in my codes. I am getting p0336 crankshaft position sensor circuit range/performance and p0452 evaporative emission control low input. which is probably unrelated. Crankshaft position sensor is new.

 

[Schurkey]

1. The coil creates spark. Of course you have no spark "TO" the coil. You might not have spark FROM the coil, and that would be a problem.

2. If you've got a crank position sensor code, that's likely the problem. The ECM causes the coil to make sparks based on the crank sensor. If it's not getting a crank sensor signal, it doesn't know when to fire the coil. Fix this problem first. There's a procedure in the service manual, which you should follow. Even if the sensor is new, the wire harness connecting it to the ECM is not. The manuals are a free download linked-to from a thread on this site.
www.gmt400.com/threads/88-98-service-manuals.43575/

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

 

[scrapyardbound98]

We got a new pigtail for the crankshaft position sensor, and got that code to go away, the only code now is the evap code. I have three mechanics looking at this truck and no one seems to be able to figure this out. Still no spark. The only thing I can think of now is the four pronged pig tail to the coil. Thank you for the service manual, I am going to be reading this now.

 

[Schurkey]

WHERE and HOW are you checking for spark? Be specific.

Does the scan tool show engine rpm when cranking?

You've replaced the distributor twice, but no mention of aligning the cam sensor signal to the crank sensor signal. Are you within 2 degrees at ~1100 rpm?

 

[Pro439]

There is a security box that does just what you described runs shuts off and doesn’t start again but when that normally happens the security light flashes. It is possible you have a bad ICM I thought I saw somewhere that the computer needs to see engine rpm and oil pressure and fuel pressure to run

 

[scrapyardbound98]

Okay so we finally figured it out. The ignition control module that we were sold was bad, we replaced it and it started. They're dialing in the distributor now, I'm not sure of the numbers. Moral of the story is don't trust the parts that you replace. Hopefully we will get the distributor all buttoned up today. Thank you all for your help.

 

[Pro439]

Covid strikes again