300 Electric Gremlins

[ridgerunner]

Not a ranger this time but...1990 4X4 Ford F150 with 300 I6 w/ 5 speed. Starts from time to time, usually when it is dry outside. When wet out it won't start usually. Turn the key on and U can hear the fuel pump run then shut off = it will start. Turn the key on, hear the fuel pump running continuous = truck will crank but not start. It has dual tanks too. My mechanic is pulling his hair out tracing it down. Any suggestions???

 

[RonD]

So Fuel injected and TFI distributor I assume?

Ford Computers(EEC-IV) should only run the fuel pump(s) for 2 seconds when key is turned on, fuel pump will not start again until engine RPMs are above 400.

So the fuel pump coming on and the NOT going off could be a computer issue or a Fuel pump relay issue.
Fuel pump relay should be on the inner fender maybe under fuse box, and it will have a Green Base.
The relay gets 12volts when key is turned on but has no Ground, the computer controls the Ground, so that Ground wire to the computer could short to Ground cause pump to run, or computer circuit is bad

 

[ridgerunner]

Thanks I will relay that to them and see what happens.