4.3 ignition problems

[dcarter21]

I'm at a loss with this one guys. I had a friend bring me a 99 GMC Jimmy with a 4.3 v6 in it. I was told the vehicle just stopped in the road on him. After a little investigation I found that it had good fuel pressure but had no fire from the coil to the dizzy. After pulling out my test light, I have fire to the coil ( pink 12 volt) but a constant light from my ICM signal wire (white black stripe wire) while cranking. I have tried replacing the coil, crank position sensor, and the ICM. I still don't have spark from the coil.
All of the fuses checked out good also. Any ideas of what could cause this? I think the constant light maybe because I'm using an incandescent test lamp.

[firebird_1995]

Possibly a different design but I had a 93 vortec 5.7 with a similar no fire condition and the hall effect pickup coil in the distributor was bad. Can't remember the exact name but its what tells the coil to discharge. May be worth a check.

[dcarter21]

I belI've it is a different design it has a electrical connector in the dizzy, but it serves as a hall effect cam sensor for firing the spider injector if i'm not mistaken. Its worth shot, thanks for the reply!

[dcarter21]

Ps where did u find a 93 vortec 350. I thought the first year for vortec was 96?

[firebird_1995]

Ehh it was in a caprice cop car. lol Maybe it was something else, but yes the injection was what it was for. Sorry I'm not any help.

[94Blackbird]

Ps where did u find a 93 vortec 350. I thought the first year for vortec was 96?

The Vortec name has been applied to truck engines since the 80's

[dcarter21]

The Vortec name has been applied to truck engines since the 80's

True the first year the name was applied to an engine was 1988,but it was applied to a v6. The first year for a true vortech v8 engine was 1996. The difference was the heads and fuel injection system.
The 95 V8 engine still shared the angled 12 bolt intake pattern of an old sbc ,whereas in 96 the vortech 5.7 heads have a combustion chamber design similar to our lt1 and a 8 straight bolt intake.
95 5.7 has swirl port heads and is tb injected
96 has vortech heads ( what makes it a vortech engine) and mfi (multi port fuel injection)
http://en.m.wikipedia.org/wiki/GM_Vortec_engine

[dcarter21]

Update: I ran my test lead form the + side of the battery to the B (white wire on the ICM). pin out say its the ignition control signal wire from the ecm. While the key is on I apply my test light to the B wire and the coil will fire. It will only fire once though. Any ideas guys.