Where does PCM relay ground to in 93 Fox?

[MBooze22]

Where does the PCM relay go to ground in a 1993 5.0 LX Hatch?

It’s an oddly specific question, I’ve been having trouble with my fuel pump relay not priming when the ignition is turned on for any period of time. When bypassing the ignition by giving the self test connector power the FP relay primes and the fuel pump runs. This led to me locating the PCM relay and testing the voltages of the yellow (always hot) wire and the red and green (signal from ignition) wire. I’ve narrowed down the issue by determining that the yellow wire is supplying 12 volts from the battery to the PCM relay and the ignition is properly signaling the PCM relay to prime when switched on, but even after feeling the PCM relay prime and click in my hand, it is still not sending power through the red wire to the FP relay. This leads me to believe that there is an issue with the black and yellow ground wire on the PCM relay because every other wire seems to be doing its job. I’ve been trying to locate were this wire goes to ground but I can’t seem to locate it. If anyone has had a similar issue please let me know. Thanks

 

[Bullitt347]

Is it imperative that it go to ground in the factory location?
Or are you willing to just take the ground wires from the relay to a known good ground?

 

[AeroCoupe]

The ground is on the coil side of the relay so if it clicks then the ground is working. Other possibility is the ECU is starting to go south as the capacitors and other parts in it are aging out.

 

[evintho]

Factory PCM relays have been known to go bad after 30 years. I was having driveability issues with my '93 drivetrain swapped into another car. Pulled the PCM relay, tore it apart and found corroded contacts. Replaced it and all is good.

 

[Blown88GT]

Where does the PCM relay go to ground in a 1993 5.0 LX Hatch?

It’s an oddly specific question, I’ve been having trouble with my fuel pump relay not priming when the ignition is turned on for any period of time. When bypassing the ignition by giving the self test connector power the FP relay primes and the fuel pump runs. This led to me locating the PCM relay and testing the voltages of the yellow (always hot) wire and the red and green (signal from ignition) wire. I’ve narrowed down the issue by determining that the yellow wire is supplying 12 volts from the battery to the PCM relay and the ignition is properly signaling the PCM relay to prime when switched on, but even after feeling the PCM relay prime and click in my hand, it is still not sending power through the red wire to the FP relay. This leads me to believe that there is an issue with the black and yellow ground wire on the PCM relay because every other wire seems to be doing its job. I’ve been trying to locate were this wire goes to ground but I can’t seem to locate it. If anyone has had a similar issue please let me know. Thanks

 

[Mcmahst]

May be useless info, but when I was trying to find the same on a 1991 TBird 5.0, the ground ended up under the passenger sill plate, where the fuel pump wiring was routed. Again, may be useless info.

 

[Boostedpimp]

The ECU grounds the fuel pump relay to turn it on. The PIP sensor in the distributor turning is what keeps it running. There is also a power wire, with a fusible link by the starter solenoid. If that is blow though, you would not have fuel pump or spark. I would verify grounds are clean but my money is on the ECU failing being it. If it were me I would try swapping out the ECU relay since your already there and test it. If it isn't the issue then I would just yank the ECU and open her up. Look for any burns, leaking caps, etc.