My 89 F 150 dies (loses all electrical power) when the key is turned to the on position. The battery is fine. It has a new solenoid switch. If I connect a battery charger to boost the power the fuel pump will respond. Sometimes normally (run for a few seconds then stop), sometimes it will continue running, other times with the switch "on" I can honk the horn and the fuel pump will re-engage. If I disconnect the battery charger and turn the switch "on" I can hear a light buzzing sound. I can feel a click or vibration in the fuel relay. What gives? do I have a bad fuel pump relay? Would this keep the engine/starter from even turning over?

 

It sounds like you have some seriously corroded battery cable connections..

Clean all the cable connections (both ends) , and if you have the "clamp on" cable ends at the battery be sure to take them apart and clean there too..

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