Ksully

2001 Chevy Express 3500 5.7; 186,000.

I bought this with about 175,000 in 2017 and only put about 200 miles a month on it; It has ran great with no issues until a few months ago. Heavy rains and leaking power booster got the ECU wet and caused a no start condition. I fixed that by replacing the booster and master cylinder, cleaned up the ECU connections, checked all the connections; no corrosion on the ECU or wiring; it started up right away and worked for about a week. I filled up with gas and the next day the check engine light came on with P0171 - too lean, bank 1; the next morning, it cranks, but won't start; the scanner freeze frame at the time of the code has the fuel trims for both banks 1 and 2 at 32 & 33%, combined ST and LT.

Fuel pressure reading with KeyOn is 60psi; immediately drops to 50 (in 30 seconds); after 5 min = 48psi; 30 min= 40psi

I intitally thought it was the Fuel Pressure Regulator, so I replaced the spider assembly with a rebuilt one because it was leaking, a few broken o-rings. It also came with a new FPR. But, alas, no change in the pressure readings.

I then changed the fuel filter but still won't start.

There is spark, although I'm going to re-check that with a calibrated spark tester just to be sure the spark is strong enought; MAF is clean. no visible issues with the distributor, nothing to indicate a vacuum leak, no visible damage (I don't think a vacuum leak would cause a no-start). No misfires. Like, I said, it ran great up to this point. The fuel pump runs and there is inital pressure. My question is, is the intial 60psi enough to start the engine? The specs should be 60-66 psi. The dropoff in pressure indicates a failed check valve in the pump, right? Is there anyway to test this?

If 60psi can't start it, then the pump is too weak to provide the pressure?? It seems the only thing left is the pump and not knowing the history, it probably needs to be done anyway. I just don't want to pull the tank without being at least close to 100% sure.

I sprayed fuel into the throttle, but that still won't start it. This has me thinking its not fuel related, but then the Lean condition?? The front crank seal is leaking pretty bad and when I pulled the crankshaft sensor, it was oily. I'm going to check the sensor again, as I did notice a bit of wire was exposed. I still need to test it to make make sure its sending a signal.

I appreciate your help and look forward to your thoughts.