I have an L98 with LT1 intake, small cap distributor, and MAP setup. The engine cranks and gets spark but won't start. I got noid lights today and found that the injectors are not firing. They are getting +12V power but the ground isn't closing. I'm assuming the ECM isn't seeing a signal of some sort but I'm not sure where to go from here.

 

So the light stays off? How did you verify the 12v?

All I have handy at the moment is a 91 schem. The c11 and c12 pins (on that schem) on the ecm are the wires for the ground. Ohm one at a time while cranking to a good ground to see if the ecm cycles it there. If not, the drivers are fried, it's not getting a signal from the dizzy to fire or you have to take your foot off the gas pedal.

 

I checked for +12V with a voltmeter. I grounded the meter to the battery. So, I know the injector ground is the problem. I will check power to the ECM next. I replaced the ignition module today with a new one and that didn't help. How do I check if the ECM is seeing the reference pulse from the distributor?

 

IIRC it should be a 5v square wave?? I can't remember, but, with a new module, if you are getting spark, you likely are gettin a reference pulse.

So the noid light never came on right?

 

https://www.thirdgen.org/forums/dfi-...nce-pulse.html

I may have been right! Time to play the lottery!