I had a no start issue with the Echlin solenoid that'd been on 'Black Betty' from the PO. I ran down the diagnostics in my FSM and detirmined that I had a faultly solenoid.
It took some doing to get on account of NAPA's difficulty in getting S.O. parts from outside resources and a delay at the NAPA local warehouse but I finally got a Standard starter solenoid. (As in Standard Motor Products and the Blue Streak line of old)
Upon removing the Echlin solenoid I immediatly saw what was going on.
The contact case seems to be made of aluminum and it was oxidized, and it was bolted to the painted inner fender skirt. What this means is the ground was only via the small bolts holding the thing on
No wonder it failed.




So I took my wire brush attachment to my drill (after moving the wiring out of the way) and had at the patch where the solenoid makes contact. I then applied some dielectric grease to stave off oxidation for the time being.
Opening the package for the SMP solenoid I was dismayed to see they are now being made in China. This, despite my online reseach pointing to manufacture in Ohio, as I recall. Nevertheless this solenoids' contact was solid copper lending to continity for this circuit way better than it's predessor.



In mounting the SMP solenoid I dropped one of the wire brushed and coated bolts (go figure) and it dissapeared into the ether. If I can't find these stubby tapered bolts at NAPA I've got a pair too long in my spares I may have to modify with my bench grinder.
I got some external star washers and some self threading 1/4" bolts but on this go I tied some white thread to the bolts with a slipknot, so if I dropped 'em again I could easily find and retrieve 'em. I reconnected the battery and it arched.



So I took my trusty rubber mallet and beat on the solenoid for a bit and tried again, no arching. Putting everything back together, tried the key and I could hear the starter running and running even after I shut off the key, so I beat the solenoid with the mallet again (starter stopped) and removed the joined S and I wiring. Hit the key again and there shouldn't have been anything and there wasn't, reconnected only the (S)witch key and tried it again and the starter performed nromally and the engine started. It seems there some kind of feedback of power through the (I) terminal which goes to the coil I think. With the engine firing though, the coil must get it's power by another circuit I reckon.
What troubles me it on the Echlin solenoid the (I) wire was connected to the terminal since I got 'BB' and there wasn't ever an issue like this. Any help/ideas ?
Thanks all and a lift of the lynch lid.

Gus

 

The "I" wire does go directly to the coil on the older model cars and trucks. It sends a full 12v to the coil + during cranking when the solenoid is active. When the engine starts and the solenoid relaxes, there is no longer 12v on the "I", the coil + gets about 9v from another ignition wire with a resistor in it. The resistor is required on the Ford points ignition, as well as their duraspark II ignition systems. It's not required and wasn't used on their TFI ignitions with the computer system.

You definitely can't tie the "S" and "I" together. If you do, as soon as you turn the ignition to run, the 9v signal is going to run backwards down to the solenoid and activate it.

 

Thanks Franklin, On this application the (S)witch and (I)gnition Coil wiring is separate but held together by a little rubber modular plug.

Update: Been commuting all week and it's started up without a hitch with the (I)gnition Coil line disconnected, so I guess I'm good to go until I get time to do some more evaluating.
This system is a Duraspark I (Hall Effect, Magnetic) not points.