Hi,
I have been troubleshooting a no start condition in my 88 for the last week with the help of this and other forums. Happy to say that the car is running this morning but thought a post was in order for the benefit of others with the same problem.
One morning the car originally fired up and died maybe 30 seconds later. Attempting to restart just turned over but the engine didn't even caugh. I quickly realized that I didn't hear the fuel pump priming for the initial 2 seconds, tested pressure on the shrader valve by the injectors and found none. Since I've had 2 fuel pumps fail and replaced (at the shop) in the last 5 years I assumed that this one had now failed me. Pulled it out of the tank and applied power directly and it ran fine. Located and tested the fuel pump relay under the hood and it was fine as well. Suspected a Vats problem so found the leads coming from the ignition switch and verified that it was reading the correct key resistance - it was. For some reason my security light flashes when cranking but that appears to be normal, at least for my car.
I tried probing the fuel pump relay connector and noticed that the ECM was not powering the signal wire for the normal 2 seconds to prime when turning the key on. Also noticed that the voltage on the orange constant power wire feeding the relay would drop down to about 2.5v when turning the key on. It would then slowly climb back to 12v when the key was turned off. Turning the key on with the ECM removed yielded a constant 12v at the orange wire.
I reinstalled the fuel pump and applied 12 volts directly to it, verified fuel pressure and attempted to start the car. It would caugh, fire but not run. I suspected that the ECM may have been fried and not turning on the fuel pump, and not doing whatever else it needed to do to allow the car to run. I pulled it out, took the case off to examine the circuit board and chips for obvious damage but none found.
Also tested each of the 8 injectors for resistance across the terminals and they all yielded 17ohms which I believe to be normal.
Consulting the wiring diagram I noticed that the orange wire is connected to power with a fusible link. I located the correct fusible link behind my battery and a resistance test confirmed it was faulty. Replaced it and the car fired right up!
The car had also been cutting out occasionally on the highway for a second or 2 and after that would not idle on its own until it cooled down. I hope this fusible link was failing slowly and at the root of that problem as well.
A.B.
I have been troubleshooting a no start condition in my 88 for the last week with the help of this and other forums. Happy to say that the car is running this morning but thought a post was in order for the benefit of others with the same problem.
One morning the car originally fired up and died maybe 30 seconds later. Attempting to restart just turned over but the engine didn't even caugh. I quickly realized that I didn't hear the fuel pump priming for the initial 2 seconds, tested pressure on the shrader valve by the injectors and found none. Since I've had 2 fuel pumps fail and replaced (at the shop) in the last 5 years I assumed that this one had now failed me. Pulled it out of the tank and applied power directly and it ran fine. Located and tested the fuel pump relay under the hood and it was fine as well. Suspected a Vats problem so found the leads coming from the ignition switch and verified that it was reading the correct key resistance - it was. For some reason my security light flashes when cranking but that appears to be normal, at least for my car.
I tried probing the fuel pump relay connector and noticed that the ECM was not powering the signal wire for the normal 2 seconds to prime when turning the key on. Also noticed that the voltage on the orange constant power wire feeding the relay would drop down to about 2.5v when turning the key on. It would then slowly climb back to 12v when the key was turned off. Turning the key on with the ECM removed yielded a constant 12v at the orange wire.
I reinstalled the fuel pump and applied 12 volts directly to it, verified fuel pressure and attempted to start the car. It would caugh, fire but not run. I suspected that the ECM may have been fried and not turning on the fuel pump, and not doing whatever else it needed to do to allow the car to run. I pulled it out, took the case off to examine the circuit board and chips for obvious damage but none found.
Also tested each of the 8 injectors for resistance across the terminals and they all yielded 17ohms which I believe to be normal.
Consulting the wiring diagram I noticed that the orange wire is connected to power with a fusible link. I located the correct fusible link behind my battery and a resistance test confirmed it was faulty. Replaced it and the car fired right up!
The car had also been cutting out occasionally on the highway for a second or 2 and after that would not idle on its own until it cooled down. I hope this fusible link was failing slowly and at the root of that problem as well.
A.B.
