I have replaced my starter, solenoid, battery positive and negative cables. My 1981 Ford F150 has 12.6 volts at solenoid but only 6 volts from ignition to solenoid. What could cause this?

 

Bad connection, or bad ignition switch, or bad neutral safety switch.

The power path starts at a small wire hooked to the large terminal on the solenoid that goes to the bat +. You should see a small wire there with a fusible link in it. This leaves that terminal, and goes into the harness where it hits a splice or splices. It eventually makes it's way through the firewall on a yellow wire. This yellow wire goes to the ignition switch, and also makes it's way to the fuse box. When you spring the switch to "start", the switch puts the power of the yellow wire onto a red/blue wire which goes to the neutral safety switch on the auto tranny, or the clutch pedal switch on a manual tranny setup. From that switch it leaves on another red/blue wire, and makes it's way to the small terminal on the solenoid to activate the solenoid, and thus the starter.

If you can follow this path, I would probe the wire and check for voltage. Make sure you check it while someone is springing the switch over to start. This will put a load on the circuit and make the voltage drop. Somewhere along the way you are going to lose the voltage, and that will be the problem area.

 

Before doing the above checks you can disconnect the wire from the solenoid to the starter at the solenoid. The solenoid coil will provide the load you need on the switch circuit. No need to spin the starter for this testing.

 

Thanks guys. I am going to go and try these things this morning.