Thank-you very much for your response CB9Mile.

I put a line on the Schrader valve at the fuel rail (from an old bicycle pump) last night and fuel flew out like a fire hose. FYI, I drained it into a can for safety. I can hear the pump running like mad in the tank. So I think you're right about the pump although I will check the pressure on the weekend (mrshorty).

I will also replace the FPR.

Two questions: (the first one may seem simple).

1. I have a Haynes Guide but it is not specific for 1991 (it covers 1991 - 2001) so ALL the details are not in the book. Does my truck have a fuse AND a relay in (around) the PDB? I'm looking at a green 30A plastic thing that looks like a large fuse. I expected a relay to have three or four leads within a sealed unit.

According to the electrical diagram the vehicle has a fuse AND a relay (fuel system). Am I looking at a fuse a relay or both (the green thing). I pulled the PDB up and saw three sets of wiring going to the underside of the PTD harness but nothing that looks like a relay as I know them.

2. If the FPR was jammed closed (no fuel return) would that be enough to continuously "flood" the engine and prevent start? Next time I crank it I'm going to pull a plug and check condition.