Blown88GT
Founding Member
Resolved Fuel Pump issue - test port jumped comes on (87 LX)
- Thread starter afjLX
- Start date
Thanks everyone! I finally got it going. Decided to do one last check for grounds on the ECM. Pin 20 good, pins 40 & 60 were very flakey. Traced both wires to the engine bay where one was mounted to a bolt on the fender near the headlamp and the other was not plugged into anything. Verified continuity to these wires in the engine bay to the ECM. Crimped together and plugged into the ECM ground connector at the shock tower. Turned the key on and the fuel pump fired right up!! Car started and I drove it around without issues. I need to verify all grounds just to be safe but car seems to be running for now. Another thing I did find, the ECM main ground pin 20 goes to the chassis inside the kick panel. It’s mounted to a bolt there. Is this ok? Should I run pin 20 to the main ECM ground at the shock tower where it is linked to the negative battery terminal? Or is this chassis ground ok?
Mcmahst
5 Year Member
Mcmahst
5 Year Member
I guess I’ll just leave it be for now. I was just reading it is recommended the ECM ground connect directly to the battery ground. If I run into anymore issues, I’ll definitely just run a wire and be done with it.
The computer ground under the hood, a cylindrical connection that connects to the fender by the battery tray with a wire that comes from the ground on the battery, the wire is buried in the harness that goes up to the drivers side of the firewall. Is this wire duplicated on this setup?
TwoRockTwo
Member
I was going to suggest checking your ignition switch, as that is a common problem resulting in the EEC and fuel pump not coming on, but you can still trigger the fuel pump via the test port.
You keep saying “short to ground”, but that is 12v circuit grounded out and resulting in blown fuses, melted wires, smoke and fire.
You keep saying “short to ground”, but that is 12v circuit grounded out and resulting in blown fuses, melted wires, smoke and fire.
My ignition switch was broken so I did replace that but I was still not getting the fuel pump to come on when the key was on. The short was caused by the slosh module. So I ripped that out. I was not getting the ground switch at the ECM because of bad grounds at pins 40&60. Once I grounded those to the battery connection at the shock tower the fuel pump fired up. So I was dealing with multiple issues it seems.
I will have to trace and see. My wiring harness is modified it seems by the previous owner. I have pin 40&60 connected to ground at the ECM ground at the shock tower. They are plugged into that cylindrical connector. Pin20 is grounded on the chassis in the kick panel. It looks like someone used a self tapping sheet metal screw to ground it there. Thats why I was asking should I also connect pin 20 to the ground at the shock tower ?
I don't know about pin 20 and grounding that wire, all my stuff is like factory with few exceptions.
the factory used green sheet metal screw on ground wires inside the cab.
I need to go back and read the thread again
the factory used green sheet metal screw on ground wires inside the cab.
I need to go back and read the thread again
After doing some more digging, I found a post describing proper grounding points for the Fox Mustang by a forum member:
" 7.) The computer takes the shield ground for the TFI module and runs it from pin 20 to the chassis near the computer. "
So I am interpreting this as Pin 20 is grounded to the chassis in the kick panel just as I found it and other members have posted here.
He also goes on to mention the other 2 grounds going to the shock tower and battery ground connection:
" 8.) The computer's main power ground (the one that comes from the battery ground wire) uses pins 40 & 60 for all the things it controls internally. "
I guess I do have it grounded correctly.