car wont start, no spark
 

Car began stumbling under acceleration yesterday morning, and died a few times while rolling up to a stop. Got it back home and let it idle for a while. Still would break up while revving. No codes set my PCM. Unplugged MAF, no change. Turned the car off and did other things. Went to start it up a few hours later and no go. Cranks fine, has fuel pressure at the rail, but no hint of wanting to start. Pulled a plug and laid it on alt. bracket, no spark while cranking. Checked all fuses, disconnected and reconnected batt., still no spark.

So now I've got it up in the air, fenders back off and am looking at the extended harnesses to the coil packs. They look fine, no obv. burnt or melted wires, and they ohm out fine.

So I'm at a bit of a loss as to what to check next. Any suggestions are appreciated.

Did you retain the factory coil-pack harness plug when you did the extensions? Maybe check to insure they're fully seated?

It seems that you've covered all the obvious things... I'm not sure what else could cause a no spark condition since the car is trying to crank and you have fuel etc.

Could it be security related? I.E. the vats or anti-theft system?

There was no blinking security light or anything in the DIC to indicate a security system problem. All of the coil plug were securely seated with the locking pins in place. I suppose I should bust out the service manuals and see if there is a multimeter test for the harnesses. But I have to say, at the moment I feel like doing nothing at all to it, ever again.

I was supposed to be leaving for Indianapolis tomorrow for a car get-together. I guess I should feel lucky that whatever failed failed here and not 600 miles away.

Uplug the MAF and try to start it up. If it runs, then you may need a new MAF. I found a similar problem that someone had with an LS1. Same thing, no spark, but everything else checked out. It's worth a shot, good luck. :cheers:

Edit: I should read more closely, and not scan through!

Check all the grounds.......classic symptom........didn’t see you mention it Joe


http://forums.corvetteforum.com/c5-t...tion-long.html

I sure was hoping it was the MAF, and youre right it sounds like exactly that.

Will def. check. The thing that is puzzling to me, is that the lack of spark is total. If it were related to the extended harnesses I would have expected one or the other coil packs to be out, not both. So a loose ground or some other problem like that seems likely.

The 3 common things that would affect ALL coil packs (both banks) are...

PCM fuse #16 underhood (10a).
Ground G106 (located near the starter I believe) and G107 (ring terminal on rear of left head)
Ignition relay 42 (this failing to close should produce a code though).



Fuses #22 (15a - coils bank 1) and #18 (15a - coils bank 2) also worth checking, but both would have to be out to affect both banks.


:cheers:

W00t! It was the back of head ground! Running like a top again. Thanks a bunch for the ideas guys!

Tom saves the Day! :hurray: :cheers:

:cool1: Glad you got it going.

AT&SB suggested it 1st, so I can't take credit for this one, other than offering more detailed clues.

This particular issue is semi-common to read about following a head swap project, but to happen out of the blue, not so much.

As you've learned, that little ground point is quite vital though - lacking it shuts down both the coils and injectors.


:cheers:

Glad it was easy..........I have never had it, But more than a few have I have helped.....hold the phone closer so I can see the problem :seeya:.....no codes is the 1st clue! My nephew had the same deal also..............it was in town dead on the road. Finger tight got him home:cheers:

Awesome :)