Starter/Relay/Ignition Switch Problem

[RSOHC]

When I crank the engine when the battery voltage is low, the starter engages with the fly wheel, does not disengage and the engine does not start.  When I am trying to start the engine I can turn the ignition key to the aux position and run position and the starter continues to crank the engine.  I need to disconnect the battery to disengage the starter.  The distributor has a Petronix conversion.  The starter is of original style.  Will this problem go away with a fully charged battery or does something need to be replaced?

[Tired Sheep]

Replace the starter solenoid

[Rbwiii]

And make sure it is grounded Very Well...

[Poor Ron]

Ford solenoids need voltage to engage & to disengage.
Low voltage is probably the problem.

[Rbwiii]

And make sure it is grounded very well....

[68stangcjfb]

Is it a reproduction? I've seen at least 3 reproduction starter solenoids fail the exact same way. One in my own car and two others. Yet the original one in my 68 Torino is still working perfectly. If you can find an original one, get it restored. It will probably work a lot better than the reproduction one. I assume the reproductions are Chinese garbage.

[Bill Collins]

A quick test to determine if the problem is in the solenoid is the next time this happens, whack the solenoid hard with the handle end of a large screwdriver. If it disengages the starter, you have located the source of the trouble.

[RSOHC]

who is the manufacted the original solenoid and what is the part number?

[Bob Gaines]

who is the manufacted the original solenoid and what is the part number?

Your 68 will have a Autolite with a C7 engineering number stamped into the top of the solenoid .

[TedS]

A quick test to determine if the problem is in the solenoid is the next time this happens, whack the solenoid hard with the handle end of a large screwdriver. If it disengages the starter, you have located the source of the trouble.

From the movie "The Longest Day"..
Capt. Colin Maud: [walking up to a stalled vehicle] My old grandmother used to say anything mechanical, give it a good bash.

[Bob Gaines]

A quick test to determine if the problem is in the solenoid is the next time this happens, whack the solenoid hard with the handle end of a large screwdriver. If it disengages the starter, you have located the source of the trouble.

For those not familiar with why Bill sometimes assaults a defenseless solenoid with a large screw driver handle is because the internal contact points get misaligned or were never aligned properly to begin with. This causes a less then full contact of the points. With all the current traveling through the points a smaller contact patch can cause resistance (like what happens on a electric stove burner). They can heat up to the point of contact surface slightly melting and welding them together causing the stuck situation . The sharp blow can sometimes knock the spring loaded points back apart. The blow doesn't repair   The problem is typically only corrected until the next time. Always be careful when adding or taking off cables on the solenoid. You need to have a wrench on the inside nut besides the one you are tightening over the cable so as not to allow the post to twist. Those thread posts directly effect the alignment of the contact points inside. A slight twist of the thick thread post is all it takes to misalign the contact points. 

[RSOHC]

The part number for the starter solenoid is C7AF-11450-A1 Autolite

[Bigblock]

My $.02. I never had this problem until converting my 67 and 68 390 cars over to Pertronix II. And it would happen during prolonged cranking like heat soak. I replaced one solenoid with a C7 from Green sales and continued to have the issue. A call to Pertronix said to add a diode in the wire to the 'I' connection on the solenoid. Their comment was the Pertronix connection to +12 v can be feedback to the solenoid and keep it engaged. Put the diode in the 67 and problem never re-accured. But since after heat problem Pertronix coils I've gone back to the points and ol yellow top.