I have a 1980 F100 Straight 6, 4 speed manual truck.
The truck was running and driving just fine when it was dropped off at my house last year.
A few months goes by and I need to fire it up and move it around. I turn the key and the solenoid engages (I can hear it clunk once) but the starter motor doesn't move at all. I turn the key off and try again but now I have no power at all. No lights on the dash, no radio, no cab light, no head lights, etc.
Long story short, after the next few weeks I replace the battery, starter, alternator and start solenoid. I also replace the ground cables, positive cables and battery terminals. I have since had the new starter and battery restested and they test fine. I replaced the starter solenoid again but no change.

I turn the key to the on position, the dash board lights up, radio comes on and cabin light comes on. I turn the key to the run position, I head the solenoid clunk once but the starter doesn't engage. I turn the key back to the ON position and no lights at all. Key on, off, start, off, on, etc does nothing. No lights, no radio, no solenoid clunk or anything. If I disconnect the battery and reconnect it; I get my lights back but when I try to start the truck again, the solenoid clunks once then everything dies.

If I remove the cable that goes from the solenoid down to the starter I can turn the key to the start position and the solenoid clunks but now when I turn the key back to the ON position, I do not lose any power. All of the lights are still on. I can turn the key back to START and the solenoid clunks again. Over and over I can do this with no trouble. But when the starter cable is placed back onto the solenoid, I go back to one clunk of the solenoid then deadness.

I tried taking the starter cable off of the solenoid and (using jumper cable) jumping the positive terminal directly to the positive terminal on the starter. When I do this, I get a massive spark at the positive terminal of the battery and it tries to melt the terminal.

Today I double checked to make sure the engine wasn't locked up by turning it by hand. No problems. I also took the starter motor and battery back up to the parts store to have them testing and they both test fine. Starter fires right up at the store and the battery tests perfect at 800 CCA.

I am at a loss as to what the trouble could be and was hoping someone on here has had the same trouble. I checked the FAQ links for the past hour but couldn't find anything exactly like my trouble.

Any advice would be appreciated.

Thanks!

 

Bad connection somewhere in the battery cables.

 

With the headlights, dash lights, radio and all of that working just fine when the starter wire is not hooked to the solenoid; I wouldn't expect this to be a battery cable issue.

I have the positive cable from the battery going to the solenoid, then from the solenoid to the starter.
I have one of the negative terminal cables going to the frame then from the frame to the engine block. The other negative cable is going to the ground terminal on the alternator.

Unless there is something else I am missing; that is all of the battery cable connections there are.

 

One (or more) of the connections is not making good contact. Without the load of the starter, it works, but adding that huge draw is enough to over power what the bad connection can handle.
Start checking them all for cleanliness and tightness. At some point, you should find one that is the problem.
Also, don't overlook the smaller wire(s) that go on the hot side of the solenoid. Everything is powered thru those smaller wires, except the starter itself.

 

Ground wire. 99% that's what it is.

Look and see if it still has the original ground cable that goes from the battery to the frame to the engine. If it does, that's your problem. If not, still make sure they're good. Also, they can look good from the outside but be bad inside.

If the grounds are ok, check the positive side. One of my Bronco's the PO replaced the terminals with the clamp on ones and I had a bad connection there. When I tried to start it I lost all electrical power for a bit and it came back a little later.

Lastly, make sure your battery terminals are clean as well as ground connections.

 

Welcome to the forum, Uncle Paul!

When you replaced the cables [mentioned in 1st post], did you thoroughly clean the engine block, frame and terminals with a wire brush? Were the bolts in good shape so you could properly tighten them?

On the six cylinder engine, the ground cable goes from the battery post to the frame and then to one of the two bolts which secure the starter.