I've got a 1978 Ford F-350 dump truck. I recently replaced the battery, solenoid, starter, flywheel, clutch, fuel pump, etc, etc etc. After replacing the battery, I have noticed that the battery seems to be discharging quickly when starting. I took the truck to the parts store to have the alternator tested (one of the only parts on the truck that has not been replaced). They concluded that the alternator needed replaced, but in the course of the testing, my battery discharged, so I needed a jump. When the cable touched the pos. terminal, the truck began to turn over with no key in the ignition! The parts guy said it was being caused by the starter solenoid, so I replaced it on the spot. The truck still needed a jump, so we tried it again and it worked fine. I drove home, turned the truck off, tried to restart, and the battery was totally dead. I put the battery charger on for 1/2 hr. and it started fine. Turned it off, and it restarted just fine. Once again, started fine. OK, I'll take it for a spin. I go to the parts store again ( cause I know if it fails here, there is a jump just inside). I turn the truck off and restart, no problem. I try it again, the engine cranks once and the battery dies. I get the guy to come jump it again, and the truck begins to crank over again. What the heck! Nobody so far seems to know what could be causing this. The only thing between the battery and the starter is the solenoid, but this is the 2nd brand new solenoid I've installed on the truck. HELP!

Change out the alternator... my jeep use to do that.. I would turn the key and it would try to turn over but wouldn't.. then I try to turn it and lights come one... next time nothing happens... its just your battery is not getting a charge from your alternator.

How about the ignition switch? If you wanted the engine to turn over as soon as you hooked up the battery, you would have to have someone keep the switch turned to the start position while you hooked up the cable to the battery. I believe the solenoid needs power from the ignition switch in order engage and complete a circuit to the starter.