fuel pump randomly stays running when key on engine off.

1986 efi 302. new relay and pigtail and filter. randomly you turn the key on and wait and it may or may not stop after a few seconds. If it does not stop running the truck will not start. What could be causing this condition? Thanks

Late answer, but for anyone who lands here with the same thing. On an '86 EFI truck the computer runs the pump for a second or two at key on and then shuts it off until it sees the engine turning. If the pump keeps running AND the truck won't start, the computer usually isn't waking up properly, because the same computer that shuts the pump off also fires the injectors.

Since the relay and pigtail are new, check these next. The EEC power relay (a separate relay from the fuel pump relay) and its fuse link. The computer's ground wires, including the engine-to-body ground straps. And the big connector at the computer for corrosion or a loose pin. Next time it happens, check for battery voltage at the computer's power feed with the key on. If it's missing or low, you've found it. These early computers also fail with age, so if power and grounds are good, a known-good computer is the next test.

Dana