Crank No-Start/Idle 91 ZR-1
 

Hello everyone, I have been a long time reader of these forums and the information has been quite helpful. I have a 91 ZR-1 that has been plaguing my existence. I first diagnosed a crank no start as a bad ECM due to lack of injector pulse and continuity to ground through ECM when cranking. Had the ECM rebuilt and the thing started right up and ran like a top for 3 days. On the 4th day I shut the vehicle off and when I went to restart it, it died instantly. I have initial injector pulse for cold start key on for all injectors. It cranks, fires off of initial pulse fuel, then dies within 2 seconds. I have good spark at all plugs, good cam and crank sensors with good continuity to ignition control module. The only thing i am losing is injector pulse once cranking. I have no ECM or CCM codes. Could the ECM have gone belly up again? I have hit a wall and would appreciate any feed back or additional diagnostic routes that I have not explored. I have a FSM for the vehicle as well.

Re: Crank No-Start/Idle 91 ZR-1
 

Try these two suggestions.

Is there a VATS lockout? With the door open and the ignition key off the Security light should be blinking. Close the door and try to start the engine. Is the Security light off when you have the ignition key on?

Observe the fuel pressure when the engine is cranking and not firing. The fuel pressure must be over 30 psi for the engine to fire. What is the fuel pressure while cranking?

Marc

Re: Crank No-Start/Idle 91 ZR-1
 

Security light flashes normally. Key in and ignition on, security light goes out. Starter cranks normally but engine will not continue to run. Fuel pressure is good and does not fluctuate while cranking.

Re: Crank No-Start/Idle 91 ZR-1
 

The future of your ECM is not looking good. Maybe it has a poor internal connection. Have someone bang on the ECM with their hand while you are cranking the engine. Beyond that, try to find another ZR-1 that you can swap ECM's with to confirm the defective ECM.

Marc

Re: Crank No-Start/Idle 91 ZR-1
 

I will give that a shot. Don't know of any other C4 LT5s in the area but I will be on the lookout. We had the ECM rebuilt so it has a warranty. Thank you very much for the help.

Re: Crank No-Start/Idle 91 ZR-1
 

May I ask who rebuilt the ECM?

Re: Crank No-Start/Idle 91 ZR-1
 

ZR1ecm.com. Sorry I was away for a few days.

Re: Crank No-Start/Idle 91 ZR-1
 

Thanks. Never heard of them but if they CAN truely fix a ZR-1 ECM that would be wonderful. Your experience with make makes them look kinda shady.

Re: Crank No-Start/Idle 91 ZR-1
 

I wouldn't label them shady quite yet. We have been in communication with them and so far they have tried to help resolve the issue. The rebuild did come with a warranty. All we can do is give them a chance to fix the issue if it is in-fact a defective ECM. I have a couple more advanced diag steps to try. I am going to try to mimic a crank signal from the Ignition module to the ECM to see if I get injector pulse, if that does not show results the ECM is definitively the issue. I will do my best to update.

Re: Crank No-Start/Idle 91 ZR-1
 

I have finished performing the more advanced testing, continuity and resistance testing of all fuel injection related wiring. All results point towards a faulty ECM. I did notice that the engine bay was dirty when it left after the last ECM rebuild, and then when it came back for more diag into the selective ride system, the engine bay was very clean. water intrusion could be the culprit to the rapid ECM failure. Will post what the rebuilder finds.