I have searched and searched here and elsewhere and cannot find an explanation to this:
My son's 1987 F150 (Std shift) 300 inline 6 will not crank. I changed out the ignition key cylinder because it seemed really sloppy and the solenoid because I never heard it click when the new key was turned. The small connector to the solenoid was just hanging there disconnected (he did some troubleshooting on his own). I have searched and found differing opinions as to whether that connector goes to the I terminal or the S terminal. If I remember oin my classic mustang the I went to the coil and S was from the key. If someone can solve that mystery for me once and for all I'd certainly appreciate it. However, I have an even more perplexing issue. I measured the voltage at the small connector when the key was turned and only read 6.6 volts. I expected to either see 12V or nothing. Does this sound like a ground issue or if anyone has seen anything similar I'd appreciate any help. Oh yes I charged the battery as well.

Thanks in advance,
Rick

 

its real common for that connector to come loose , there is no choice where it goes back onto , the connector is on the solenoid , might tighten , crimp , it so it stays on

 

The small wire goes to the "S" terminal only.
The "I" terminal gives full voltage to the Ignition Coil while the engine is cranking if used.
Some older 460 (7.5L) with the carburetor used the "I" terminal to run the fuel pump.

 

Also check the clutch switch and the Ignition switch. The Ignition switch or its plug can melt and cause a voltage drop.
Also make sure the starter solenoid on the fender is grounded to the fender and you have a ground wire (>=10GA) going from the NEG post of the battery to the fender and body (not the frame). Make sure the large NEG large battery cable is bolted to the starter mounting bolt.

 

I have been wondering about the ignition switch as well. Do I have to drop the steering column to get to it? From what I have read it is a PITA to get to. Thanks for confirming the I vs S terminal issue. I didn't think about the clutch switch because I was getting 6.6 volts at the small wire to the solenoid. Is that bad logic?

Thanks again,
Rick

 

Make sure your meter has a good ground but better yet do not use the meter as it may throw you off the cause.
Use a loading test light with incandescent bulb to check the circuit when the key is turned to the start position.
Any bad plug connection or bad contacts in a switch can cause it.
You just have to start where you have power on the wire with the key turned to start and check along its route to the starter solenoid.