Join Date: Feb 2005
Location: Atlanta, GA
My Ride: CSX/CS/GLHS
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Re: 1986 Shelby GLHS Omni Wiring & Vacuum Diagrams
Hi Errol...I will take a look through this in the morning. I'll do my best to help you out. My first impression is that I would tell you that there is a single wire from the logic module to the power module that tell the power module to close the ASD relay. The ASD relay provides the ground for the fuel pump, the coil and the fuel injectors. So if the circuit between the logic module and the power module is interrupted somehow, the ASD relay never gets the signal to close the relay. If you ground the ASD relay at the diagnostics connector (blue/yellow wire attache to ground) and turn the key on, you should have 12 volts to the fuel pump, the injector harness and the coil for about 1 second. Then the ASD relay will open again. This is by design. If you then crank the engine, and everything is working, the HEP will send a signal to the logic module while you are cranking and when the logic module sees the HEP signal, it will re-energize the ASD relay wire causing the ASD relay to ground the circuit again and the car should start.
If the ASD relay works when you ground it at the diagnostics connector and turn the key on, then the ASD relay inside the power module is not the fault. In that case, you would possibly have a wiring issue between the logic module OR maybe the logic module is faulty and the circuit that feeds that wire is dead/faulty. I have had two logic modules that were fine otherwise but the car would not start unless I grounded the ASD relay at the diagnostics connector...then the car started and ran fine, but the fuel pump would run all the time, even if the engine was not running which defeats the purpose of the ASD relay in the first place. You don't want the pump to continue to run anytime the key is in the on position, which would most likely be the case after an accident. The HEP would stop sending the signal to the logic module if the engine quit, causing the ASD relay to open and stop the fuel pump...again this is by design.
The fuel pump will charge for about 1 second each time you turn the key to on for 2 maybe 3 times, but after that, it will no longer charge/prime till the logic module seems the HEP signal. The purpose of the initial 1 second charge is to prime the fuel rail and try to build enough fuel pressure for the engine to start running more quickly, other wise it is slow to actually start while the pump builds pressure while you are cranking.
As a test for a bad logic module, try grounding pin #17 of the red connector. If the car then starts you have either a bad connection at the logic module on pin 17 or the logic module has a bad ASD ground circuit and must be replaced.
If it still doesn't start, the verify you have continuity on the ASD Relay Control Circuit from the LM Red Connector Cavity #17 to the PM 12 Connector Cavity 5. If this circuit is open, you have a connectivity issue/broken connection between the logic module and power module.