This is a weird problem and I'll try to keep it brief. My F-100 had been difficult to start when warm, barely turning at first, then spinning normally. And a side issue was an ignition switch that allowed the motor to run for a second after the switch was turned off. Then I noticed that the hot lead from the battery + to the solenoid was nearly rusted through. I changed the cable and it started up normally.
I took a friend for a ride recently and when we returned to the garage it wouldn't shut off until I pulled the coil wire. I assumed (I know, I know...) that the very old solenoid was bad. I bought a new non-OEM one and hooked it up just like the old one. Connected the negative post and the starter engaged without the key in the switch. Checked the connections--aok.
Bought a new ignition switch (spade type) and installed it--same problem.
Noticed that the negative ground went to the block with no ground to the frame. Added a block to frame ground--same problem.
Do I have a bad new solenoid? Or any other ideas?

 

sounds like possible wired wrong. wrong post is hot

 

 

What year of F100 are you talking about?

 

It's a 1972 F-100 with a 302, automatic.
And thanks, guys. I hope to get back to the garage tomorrow night to check out some of these ideas. It is by far the simplest vehicle in my garage, and this has me scratching my head.

 

The Ignition Sequence for the 1970 should be 'close enough' for this.

Ignition Switch Pin-Out and Operation

For

1970 Ford F-100 through F-350



(Connector side) (Switch side)




Ø16 & 932 Pink & Blue “C” = “Coil”
21 Yellow “P” = “Power In”
32 Red “S” = “Start”
Ø98 & 297 Black & Blue/Green “A” = “Accessory”
977 Violet “PO” = “Prove Out”
(none) (none) “PO” = “Auxiliary Prove Out”

1) In the ”OFF” position, 12VDC is present at the “P” pin. All other pins are not connected.
2) In the “ACCY ONLY” position, power comes from the “P” pin and is applied to the “A” pin (which feeds wires 297 [Windshield Wiper, Radio, instrument cluster Constant Voltage Regulator] and Ø98 [a pin on the “RED” connector that’s under the right hand side of the dash, Alternator light or gauge on the instrument cluster and, if you have idiot lights, the main Voltage Regulator]). Some of these signals pass through additional connectors that are not mentioned.
3) In the “ACCY & COIL” position, everything in step 2) applies, but also: Power comes from the “P” pin and is applied to the “C” pin (which feeds wire Ø16, for both the Ignition Coil and the Starting Motor Relay, and wire 932 (which connects to wire 640A) for the instrument cluster and (then wire 640 for) the “BRAKE WARNING LAMP”; if it is present, it also powers the Carb. Throttle Solenoid; the “BRAKE WARNING LAMP” will have power at this point, but will lack a ground to complete the circuit until the next step).
4) In the “COIL START & PROVE OUT” position (a ‘momentary-closure switch’, which means that when you release the switch, it reverts to the position in step 3)), everything in step 3) applies, including the things from step 2) before that, but also: Power comes from the “P” pin and is applied to the “S” pin (which activates the Starting Motor Relay); at the same time, a ground is provided to the “PO” pins, for wires 977 and 977A (which provide a ground through the “DUAL BRAKE WARNING SWITCH” [sometimes called ‘the proportioning valve’]), in order to prove that the “BRAKE WARNING LAMP” is working.
5) When the switch returns from the “COIL START & PROVE OUT” position, ground is removed from the “PO” pins and power is removed from the “S” pin. This shuts off the “BRAKE WARNING LAMP” and the “STARTING MOTOR RELAY” (which makes the Starting Motor drop out of the circuit and quit trying to start the engine).
6) When the Ignition Switch is turned from the “ACCY & COIL” position to the “OFF” position, power is removed from the accessories and from the Ignition Coil’s field; without a field present, the Coil cannot produce spark for the Distributor.

It's hard to say for sure, but I'd suspect the Ignition Switch, rather than the Starting Motor Solenoid.

 

 

[CROCODILE TEARS]What, you mean I was wrong again?!? Say it isn't so! [/CROCODILE TEARS]