fuel pump wont prime when ignition turned on.ran hot test lead to pump and pump operates.replaced relay ,swapped out ecm,no change. power to ecmb fuse 12v.- power at relay and out of ecm .547v with both old and new ecm.
Also have code reader but check engine lite does not come on ,lite also doesnt come on when ignition turned on , replaced check engine lite bulb still didnt work with either ecm. any suggestions appreciated, thanks

Im in the same boat. I ju8st ordered a sheffield short circuit finder to aid in my quest. it appears to be a short in one of the wiring harnesses. It may even be in an apparently unrelated harness as just prior to my problem with the fuel pump priming I had a fuse blow twice. This fuse affected my radio but wasnt the radio fuse. I forgot exactly which one but im gonna check all harnesses when my detector gets here.

Im in the same boat. I ju8st ordered a sheffield short circuit finder to aid in my quest. it appears to be a short in one of the wiring harnesses. It may even be in an apparently unrelated harness as just prior to my problem with the fuel pump priming I had a fuse blow twice. This fuse affected my radio but wasnt the radio fuse. I forgot exactly which one but im gonna check all harnesses when my detector gets here.

It was the wiring, havent found the exact place yet . short is in the always hot lead[orange wire] between fuse block[fuse ecmb] and ecm.
ran a jumper wire between battery and ecm [the orange wire] and truck started. the orange lead leaves the ecm orange and supplies power to the oil pressure switch and fuell pump relay. havent tried to run code checker yet.