ECM Issues - No Start - ZR-1 Net Registry Forums

Macroblock · 05-23-2020

I thought I should share some ongoing observations related to the No-Start condition of my 1990 ZR1. It's pointing to an ECM issue.

No negative-GND signal is present on the injector outputs from the ECM. Injectors therefore do not activate.

Vehicle turns over normally.

Fuel pressure is good. Both pumps are working.

Spark is good to each cylinder.

No diagnosis codes.

VATS works correctly.

Note: Changed the Crankshaft Sensor (right-hand underside next to dip stick entry point). No change in symptoms. Old sensor was tested and has an impedance of approximately 1 K-ohms. I suspect it was working correctly.

By removing the yellow harness from the ECM, I was able to ground each injector with a jumper wire, using the service manual as a pin guide. Doing this put a small amount of fuel in each cylinder and verified injector operation. Upon returning the yellow harness, I turned the engine over. It would ignite and/or run briefly.

Next - I will now open the ECM and look for signs of burning or corrosion on the circuit boards. After which, I will verify that each of the 8 Power MOSFETs (-) are operational.

05-23-2020	#1
Macroblock Join Date: May 2020 Location: Windsor Posts: 39	ECM Issues - No Start I thought I should share some ongoing observations related to the No-Start condition of my 1990 ZR1. It's pointing to an ECM issue. No negative-GND signal is present on the injector outputs from the ECM. Injectors therefore do not activate. Vehicle turns over normally. Fuel pressure is good. Both pumps are working. Spark is good to each cylinder. No diagnosis codes. VATS works correctly. Note: Changed the Crankshaft Sensor (right-hand underside next to dip stick entry point). No change in symptoms. Old sensor was tested and has an impedance of approximately 1 K-ohms. I suspect it was working correctly. By removing the yellow harness from the ECM, I was able to ground each injector with a jumper wire, using the service manual as a pin guide. Doing this put a small amount of fuel in each cylinder and verified injector operation. Upon returning the yellow harness, I turned the engine over. It would ignite and/or run briefly. Next - I will now open the ECM and look for signs of burning or corrosion on the circuit boards. After which, I will verify that each of the 8 Power MOSFETs (-) are operational.