Chevrolet Repair: ecmb and fuel pump on a 1987 Blazer, oil pressure switch, fuel pump relay

Question
Dear Sir,
I recently purchased a 1987 Chevy S-10 2dr Blazer. 2 yrs ago the truck was my father's and it ran fine, however, for the last yr it sat as it quit running(New owner was not reliable to be able to advise of any problems.  It has a 2.8 V-6/automatic.  

When I brought it home, I put a battery in it and gas.  It would not start, as the fuel pump was not pumping.  I removed the pump from the tank and bench tested it, it worked.  As I started to check fuses, I found the ECMB fuse was blown.  I replaced it only to have it blow again.  What does the ECMB do, and what else can i check since the fuel pump does not seem to be getting power?  

Answer
Hi Mark,
ECM is engine control module. I think the B is battery power to the ecm, but I'm not sure.
The manual I have is for newer Blazers, but it has fuel pump relay, oil pressure switch for fuel pump, voltage regulator, etc. depending on the fuel system, so you need to look at a diagram for your specific vehicle.
Most of the items seem to be things that are powered by that fuse, but then grounded by the ecm to complete the circuit.
The oil pressure switch I mention is on almost all fuel injected GM's. It is a backup system to operate the fuel pump if the relay quits.
I doubt the problem is the ecm, since it is just completing the ground in those systems.
But I would unplug the relay, and oil pressure switch, to see if one of them is shorted to ground.
I have seen the power wire to the fuel pump get pinched between the fuel tank bracket and the frame, and shorted also.
The public library, refference section, is a good place to look at, and copy, manuals and diagrams.
They have loads of manuals.

Good luck,
Van