I replaced the junk plug wires, cap & rotor but the engine still wouldn't fire. I re-verified that I'm getting a spark and then decided to test the fuel pressure. The pressure with the pump forced on was 55 PSI, way above the rated 38-44 PSI. I can smell fuel when I crank the engine so I think the injectors are triggering (or perhaps just one is).

My manual says to replace the fuel pressure regulator. OK, I can do that - but would this problem be likely to suddenly cause my truck to quit running? I want to make sure I'm tracking down the right failure.