I have a 91 K 3500 with fuel pump run on

[Ray62406]

Hi, I have been battling a problem with a fuel pump run-on problem with a 91 K 3500 with a 7.4 litre and standard tranny. The problem is not constant, I have not been able to pin it to a certain condition. Most times it shuts off when the vehicle is shut off but every once in a while you can go out as much as 45 minutes later and the fuel pump is running. The relay has been ruled out, it has been replaced. You can hear it engage when it is reinstalled.
I've scanned the ecm and there are no codes present. Pulling the fuel pump relay stops the pump but it will start running again once re-installed. Pulling the fuse does the same thing. You may have to wait as much as an hour before the relay can be reinstalled without the pump running. I know the ecm controls the fuel pump and suspect it to be at fault but don't want to start replacing parts until I have a good idea of what is at fault.
Any help would be appreciated....Thanks in advance...

[MT-2500]

Originally Posted by Ray62406

Hi, I have been battling a problem with a fuel pump run-on problem with a 91 K 3500 with a 7.4 litre and standard tranny. The problem is not constant, I have not been able to pin it to a certain condition. Most times it shuts off when the vehicle is shut off but every once in a while you can go out as much as 45 minutes later and the fuel pump is running. The relay has been ruled out, it has been replaced. You can hear it engage when it is reinstalled.
I've scanned the ecm and there are no codes present. Pulling the fuel pump relay stops the pump but it will start running again once re-installed. Pulling the fuse does the same thing. You may have to wait as much as an hour before the relay can be reinstalled without the pump running. I know the ecm controls the fuel pump and suspect it to be at fault but don't want to start replacing parts until I have a good idea of what is at fault.
Any help would be appreciated....Thanks in advance...

You have crossed or shorted wire someplace.
Key off should turn off power to fuel pump relay/oil pressure switch and pcm.
Check out the ignition switch real close.
MT