Hello All,
Been a long time since I have posed a question, but I am stumped and need your help. I inherited a 1976 F-100 custom a couple of years ago and have just started working hard to get the truck running and work towards a resto. The truck was always cranked and run every two or three weeks during the last three years, driven around the block to lubricate seals etc. This truck is an electrical nightmare especially for someone like me who knows how to always wind up with his hands on the wrong wires. The truck has been cranking and starting fine until the other day when I put it under the shelter due to storms coming. The next day I went out to begin working on it some more and it would not crank over. The solenoid is on the fender, and as you attempt to crank it over the solenoid just chatters or buzzes. So I figure replace the solenoid, no dice. I pull the starter and have it checked and it is fine. I clean all connections and same result. I charge the battery same result. I change the solenoid again, same buzz. I replace the alternator, same thing. Two days before this started I had replaced the turn signal switch cam. Pull everything back apart to check for chaffing on a wire, all looked good. I had pulled the gas tank a year ago and replaced the sending unit. I have only kept about five gallons in the tank since this time. The other day I put about 20 gallons in the tank and the truck began not cranking over after I had put gas in it (it cranked and started fine when I left the station). I have no instruments due to so many wires being disconnected. I have replaced the instrument cluster and circuit sheet but do not have the main harness connected. I have also tried disconnecting the trun signal/hazard /horn harness to see if there was something that I did not see after double checking the cam replacement. Still the same buzz. Could this be an ignition switch failure? Any suggestions will be greatly appreciated. I have not tried to arc across the solenoid because I'm not sure how. I have seen it done but not tried this myself.

 

Have you had the battery tested ?.

 

Yes. I have even tried two batteries both jumped and connected directly. Pulled a relay after reading a thread on page 7 and took it to the parts place to replace thinking it was a starter relay, it was a horn relay. I never said I was smart, but I can open a bottle with my wedding ring! After talking to the parts folks, which by the way were extremely helpful, I need to get an extra set of hands to check voltage with the meter. I have a lot of tools, some of them I even know how to use. Please keep the suggestions coming. It's not rocket science, but when I was a kid mine blew up on the pad, so I started playing with fireworks!

 

Soooooooo.....not saying I'm right but this is where my mind goes.

1. Check for water in your gas. Could have a hydro-locked engine. This happened to my neighbor this week, filled up at a station that had water flood into its fuel tanks.
2. Voltage drop on the battery. A battery can read 12v on a static test but drop way low under load if it has a bad cell.
3. Check voltage to the starter while someone holds the key in the "start" position. If less that 12v you have a problem up stream from the starter.

For the ignition switch - you should see 9v at the coil in the "Run" position and 12v on the starter side of the solenoid in the "Start" position. Hopefully that makes sense.
If not in either of the above cases...you might have an issue with your ignition switch.

Let us know what you find out.

 

Check battery cables. They may be corroded inside. Make sure you have a good ground wire from the engine to the body. Check the screws that hold the solenoid to the fender. The solenoid needs a good ground connection.

 

The headers are hot on the old Ford again! I was finally able to get another set of hands so I could check voltages with the meter. As the switch was turned to the start position, the voltage at the solenoid was very unsteady. The static voltage of the battery was 12.4 volts. I removed my meter and had the switch turned again. I then noticed a small wisp of smoke and sparking on the positive battery cable. TO THE PARTS STORE! Got a new cable, size two as was recommended in another thread, and she started right up! But how come you can't buy a red cable? Thanks to those who had suggestions, I really appreciate it. On to the next project! Happy St. Pat's Day.

 

" But how come you can't buy a red cable ? " It doesn't really matter because the pos post it bigger than the neg post, so you don't mix them up.

 

Great to hear you got it running again.

 

You can in some places.
https://www.batterycablesusa.com/bat...ttery%20Cables
Congratulations on finding the problem.