Hello,
I have a 1990 GMC pickup that is blowing the Ignition ECM 10amp fuse and not allowing the fuel pump to run once I turn the key to ignition on. All we did was change the fuel filter and engine oil. The engine is a built up 355 with stock TBI and aftermarket heads with MSD 6AL ignition and coil. Truck ran fine and then just wouldnt start after changing the filter. Tried to prime the lines, and the fuse kept blowing. Installed a new fuel pump relay on the engine bay firewall also, and still keeps blowing the 10amp fuse. Even disconnected the relay and it still blows the fuse! Would a loose ignition key cause this to short out? The key is very worn out and can come out with the ignition still running. The fuel pump is about 3years old from O'Reillys, but I did almost run it out of gas a week ago. Any ideas?

Thanks for your time

aaron

Welcome to AF. Take a look for a pinched harness or short near the oil sending switch, first.

No shorts by the oil pressure sender. I did have a friend tell me that the TCC 4pin plug on the trans can go bad or the shift solenoids can go bad. I unpluged the 4pin connector at the trans and the fuse stayed together when I turned the ignition on. Trans was rebuilt about 2-3weeks ago, so the solenoid maybe be bad or loose wires on the valve body.

If you are blowing the 10a fuse, it also feeds the 2 injectors make sure you did not pinch the wires under the air cleaner, egr solenoid and evap solenoid all on that fuse.

If you are blowing the 10a fuse, it also feeds the 2 injectors make sure you did not pinch the wires under the air cleaner, egr solenoid and evap solenoid all on that fuse.
All the wires are good by the TBI. Its gotta be in the trans since we unpluged that connector and the fuse held. Gonna call the tranny shop in the morning since its under warranty.