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Discussion Starter · #1 ·
I recently took a running motor out of a 91 LX mustang and put it in a 92 Shell that had been sitting out in the rain for 2 years with no hood and missing windows on the drivers side. There is also evidence of mice and other animals being in the car.
After I put the motor in it would run for 5 to 10 seconds and just shut off. I found the problem to be is that the fuel pump would not run with the key in the on position. It would only run in the start position. I then found that if I held the key right below start, enough for the starter to disengage, the car would run. Got it up on the trailer to go to a body shop and it died and would not start again. Fuel pump would still turn on, but no start. Then even the fuel pump stopped turning on. You can jump the terminals at the relay and the pump will work.
I have found the problem to be that the terminal at the fuel pump relay that is supposed to be the PCM ground to activate the relay has power to it. We tried jumping the pump and getting it to start but there is no injector pulse. There is spark. How is there power at the PCM ground? Where might the issue be? The PCM ground by the computer is connected.
 

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You will see power there if the relay is not engaged. That's normal. What you are seeing is, a voltage being sent through the relay coil windings.

Besides the ground from the ECM. What are the voltages at the other wires on the relay with the key on? Post them up with the wire colors listed with them.
 

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Discussion Starter · #3 ·
I actually just figured out the problem. It had power at the ecm ground side of the relay. So I new something was up with an ecm ground. I took off the pcm connecter and checked pin 40 which is pcm power ground. No continuity to ground. I checked and saw that the same ground wire went to the MAF sensor. Checked there, no continuity to ground. So it said that on the Left fender apron. So I looked and looked and finally found a plug tucked down in that was hooked to nothing and I could find nothing to hook it to. So I went to the other car I found the connector for it on the inner fender apron. Took that out put it in the other car and it fired right up. Whenever the people took the motor out of the shell they took this wire and connector out with the battery terminal wire. We never unhooked it or saw the connector so had no idea it needed to be hooked to something. I just don't understand how it ran for a little while without that being connected.

The joys of messing with previously hacked vehicles.
 
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