hi i have a 86 f 250 302 fi , my issue is when i try to start the truck the solenoid just buzzzzes nothing to the starter, battery is good and it actually only does the buzz when i jump the battery and try to start it, if i dont have a jump on the battery , when i turn the key nothing happens except i losse all power, dome light fuel gage , dash light everything , then within a few minutes it acts like it resets itself and i get power back in the cab, frustrated, cant figure it out , any ideas would be great.

 

If your battery is good,, you have a bad connection or cable. I am wondering how you know the battery is good. I hope you did not just put a meter on it and it gave you 12v. If you do have a meter, you can check the battery and the cables by putting the meter leads in place, and checking the voltage WHILE THE KEY IS BEING TURNED TO THE CRANKING POSITION. You can do troubleshooting with a load on the system(when the solenoid is buzzing). Checking voltages with no load tells you nothing.

Your problem is like a kink in a garden hose. The bad connection is the kink, and it's letting enough current through to run small lights and other small stuff(enough to dribble water out of the hose) but when you try to use a large amount of current(the starter), the whole thing fizzles out, just like opening the kinked water hose wide open. It will spurt for a second and then fizzle out.

 

i took the battery to the shop and they tested it for me , so would you guess maybe a bad cable to the solenoid or from the solenoid to the starter, ive checked the connections.

 

ok i must laugh at my self 4 darn hours and it turned out to be a bad positive connection from the battery, vroom fired right up,
so thank you very much for your annalogy made perfect sense to me, another happy ford on the road.
thank you very much.