Ive been having some issues with popping fuel pump fuses for the past 4 days. ive installed a new fuel pump, fuel filter, strainer. ive redone the fuel pump ground (since gm did a shitty job of doing it) and grounded it strait to the frame. also replaced a couple wires under the hood that was looking old and had better days. my problem is i fix it and it works for a day then out of nowhere it will just kill the fuse and cut off. once it does that it will just blow fuses everytime i turn the key forward and it gets voltage to it. once i get it home and mess with it it will start up like nothin ever happend. ive checked the wires from the tank all the way to the firewall with nothin found. ive read where people say that the oil pressure may cause this but dont know the exact location of this. ive also checked the fuel pump relay and it checks out fine.

 

The OPSU circuit is a backup circuit that will run the fuel pump in the event that the ECM/relay circuit doesn't work. The OPSU is located just above the oil filter. Earlier FI cars had a 2 wire OPSU in this location that only took care of the fuel pump - these cars had a single wire oil pressure sender on the china wall next to the distributor to feed oil pressure readings to the gauge/idiot light.

The later cars have a 3 wire OPSU that combines both the fuel pump circuit AND the gauge feed into one unit.

Wiring diags here to help maybe: http://www.austinthirdgen.org/index.php?pid=19

Oh - the fuse for this 'extra' OPSU fuel pump circuit is the fuse tucked in the fenderwell beside the battery (assuming your battery is on pass side) - it should be a 20 amp fuse.

 

forgot to mention this is for a 93 caprice. im hoping all is the same since its tbi still.