I have been through the ringer on this one. As stated in another post, I just bought my
first vette in 15 years, 91 vert, 49K miles really nice condition, stock L98. I only had the car for 2 days put about 250 miles on it no real problems, slight rough idle at a stop. Then it died. It would start up and run for a second then die. The car has only been driven about 3K in the past 4 years so it sat a lot.

I caved in and took it to a GM dealer, I not have a relatioonship with a good mechanic or shop yet and, I just do not have time to do the work right now. Anyway, they diagnosed a bad PCM and claimed shorted injectors were the problem. I decided to take it home since thay wanted 1700 to do the FIs and another 450 to do the PCM. I figure if that is the true issue, and I was going to replace the FIs anyway this winter, I might as well do this myself for around 1000 bucks and a lot of swearing.

I got the FSM and I have a “newbie” question regarding how to interpret the instructions in the FSM. I am just going to take my time on this but I also do not want to cause other damage to the car by trying to learn how to work on it. The electrical part of this process is what scares me the most.

I have been through the fuel supply diags and all tested good. The TBS and MAP are ok, fuel pressure is great and holds, return line is clear. I am diagnosing the starting problem and I am looking at Chart A-3B Engine Cranks but won’t run (6E3-A-24).

At steps 6 & 7.

#6 says to probe injector harness terminals with test light. Does this mean to test the purple/white wires at each injector? I assume I would ground my test light and poke each wire to see if the light comes on the test light? I should see 12V on both the purple and the white wire at each injector?

#7 If I put the noid light back into an injector plug, and disconnect the distributer 4-way, it says to momentarily touch the the harness connector circuit (430) with the test light to 12V. I am really not sure how t interpret this statement. Does this mean to apply 12 volts to the end of the harness where it plugs into the ECM circuit 430? Any suggestions on the best way to do this?

Sorry if this seems like a no-brainer question to many of you, I just want to make sure I do not toast something in the electical system, ECM while diagnosing this issue. Thanks to any and all of you who have any advice.

 

12 volts is supplied to one wire on each injector. The other injector wire goes to the ECM which pulses this wire to ground according to the throttle position, etc. Probing the injector harness means that you put the test light across each injector socket, the light should pulse when the engine is cranked. You could also test for 12v on each injector wire that goes to 12v to insure each injector is getting 12v. No 12v, then the ECM cannot pulse that injector.
I do not think it safe to connect 12 v to circuit 430 and I am sure they mean to connect one lead of your test light to 12v and the other lead to circuit 430.
I own an 87 and the injectors work basically the same as your 91, but I don't have a 91 FSM, but I am certain that my info is at least safe.

 

Thanks, I am going to work this over next weekend.