I have a 77 F250 351m. Went to start the truck and nothing happend but a clunk. I get out and test the battery got 12.86 volts. I did a load test and it tested good. I checked the solenoid and had 12v on the battery side. Tested the ignition side and had 12v then I tested the the starter side and had 12v there but didn't have the key in the start position. I unhooked the neg battery terminal. I then got 12v between the solenoid ground and the neg battery terminal. The whole truck is grounded out. I started looking for the ground and found that the ground is in the b/r wire on the solenoid. So I continue to search for the ground and cant locate it. If I give it a day and hook everything back up as long as I dont turn the key I have power to everything again. Once I trun the key the solenoid clucks and boom the whole truck is grounded again and all power is lost. This last time I unhooked the negitive bttery terminal and the three wire plug under the solenoid with the b/w wire and could watch the volts drop when I tested from the solenoid ground and negitive battery terminal. Any Ideas. It has been my dd fro threee years and just started it two days ago. Thanks

 

Have you bench tested the starter?

 

That's what I was thinking but I replaced it with a new tested one. Now I have narrowed it down to something with the ignition switch or the circuits that get powered on with it. I pulled all fusees and installed one at a time. unfortunately this was intermittent some fuses would ground the system out then it wouldn't. I'm leaning towards the ignition switch itself. I will try out my spare in the morning. Any other ideas on what would cause this. Thanks

 

You didn't say if you have a stick or auto. Make sure you have the truck in park or neutral with the wheels blocked.

Try jumping a test lead from the positive post to the "s" terminal on the starter solenoid. If it cranks then it either your NNS or IGN switch is bad.

But I read....

Clean your battery posts and terminal clamps. Sounds like corrosion causing bad connection. They need to be clean and tight...

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Find where your neg battery cable bolts to the engine block, take it off and clean it, also if it doesn't have one, make a ground cable from the engine to the truck firewall.

 

i had this problem a few days ago it took me 20 minutes
this is what you do:
1. take the starter off and with some sand paper sand the + terminal till its shiny copper
2. if the nut THE ONE THAT SCREWS IN TO THE + TERMINALON THE STARTER (holds the wire that goes to the starter from the solenoid) rusy replace it
3. now if you have a wire brush that can go into your drill (if not regular wire brush will work) brush the face of the battery (the side that bolts into the tranny) until its shiny and do it to the other side that meets that face.
4. polish up you solenoid terminals& your + positive side of the batery
5. the ground wire, i bolted it to my oil pan, and then brushed the - terminal
this worked for me and should do it fo you now after that you still here a click click click it might be you voltage regulater that may need replacing there only 20$ at your local auto parts store good luck

 

Ok heres the update. I absolutely hate intermittent electrical problems. All of the battery connections are clean and tight along with all grounds and solenoid connections. When I jump the positive side to the s terminal on the solenoid I get the same thing click and lose power to the truck, but still show 12v on both sides of the solenoid with no engagement of the starter. Each time this happens I have to disconect the neg battery terminal to get it to "reset". After resetting it I jumped power straight to the starter and it started. I shut it off and refired it with the key about five times. So i'm thinking its either the switch or the solenoid. The spare switch that I have must be from a 78 or 79 because it has a larger plug with additional wires. So I couldn't rule that out. I'll pick up a new solenoid and wait to see if it does it again. Thoughts