I'm having a hard time with this 2001 Chevy blazer 4.3L. It will crank but not start. Tested ignition module and coil and they are good. But I'm not getting a signal on the on the B terminal with white wire coming from pcm. Checked continuity on that wire from pcm to icm and its good. Put in new crank shaft position sensor and have continuity from all three wires on ckp sensor harness connector to pcm. I also have 60 psi fuel pressure . Checked for spark at plugs and have it. New cap and rotor. All fuses are good took off spider wire harness and noid lights up on all when cranking. Ohmed injectors all at 10-11 ohms. Why wouldn't the pcm send a ignition timing signal if the crank position sensor circuit is good? Security light is not on while cranking.

 

So you have spark at the plugs, good fuel pressure and proper injector signal pulses and crank but no start?

George

 

Yes I have good fuel pressure to the spider. And I pulled the harness off the spider and put a noid light in each injector harness and it lights up while cranking. I have an inline spark tester that I put between the spark plug and wire I can see light up when I crank. I cant say how good the spark is. What I dont have is that pulse signal from the pcm from pin C2 26 to the ignition control circuit B white wire. Which I thought I should have with a new ckp. I took the plugs out last night and they look fuel fouled. I also tried spraying starting fluid in in which didn't do anything.

 

I don’t think that you can have spark with no timing pulses on the white wire from the pcm to the ICM.

George

 

George I think you're right but my in line spark tester lights up while cranking. Plugs are wet when I pulled them. But I know that white wire circuit B isn't getting a signal. May be just a week spark. I cant figure it out.

 

Are you testing for spark on the high voltage secondary side (coil output or spark plug) or one of the primary low voltage signals (input to coil)?

George

 

I put a spark tester that's basically like a light with plug wires going in and out of it. I hooked one side to spark plug other side to plug wire. Also did this at the coil to coil wire going to the distributor cap and the like pulses when I crank it. I didn't think this was possible without the pulse signal from pcm to icm. But I've checked and triple checkch.

 

I pulled AC delco R44LTS6 spark plugp out of it. Does that sound like the plugs that came from the factory? It's a copper plug.

 

The proper way to check spark is to verify 1” of blue spark across an air gap at the spark plug end of a plug wire.

George

 

You're right George. I'm gonna recheck that and report back. Due to all the fuel on the plugs I'm pretty sure that isn't gonna be good spark. I appreciate the advice.