I'm going to use a Ford style starter solenoid in the Duster. The case makes the ground path so the neutral starter switch is not needed. I haven't looked for a Ford wiring diagram, anyone know how they provide the safety feature? I suppose I could use the stock switch to ground another relay that closed the loop.

iirc the older fords used a switch in the steering column for the neutral saftey , not sure how the newer ones did it, I know they had a one post and also a two post solenoid.

just wire through whatever you are using as neutral safety to the ford solenoid.

unless you isolated the relay with something like those msd rubber mounts then used the wire from the shifter to ground the case of the selonoid

There are 2 styles of these solenoids.

A 3 pin, 2 large, 1 small, - the two large are the high amp studs to run the starter. These types are typically grounded through the case to whatever it's bolted to. They are engaged by putting 12v to the small terminal, usually from the starter switch, through a neutral safety switch to the solenoid.

A 4 pin, 2 large, 2 small. The large studs function the same. One small stud is for 12v to energize the solenoid, usually a single wire from the start switch. The other small stud provides the ground for the solenoid windings. Usually run through the neutral switch to a ground. This provides ground for the solenoid only when in P or N. This is the one I prefer. It's simple and uncomplicated to wire. And doesn't rely on being grounded through it's mounting. This is also how the factory starter relays worked and are best if using the Torqueflite NS switch.

There are also 4 pin solenoids that provide a 12v circuit for the ignition when the starter is engaged. These are usually grounded through the case as well.

A circuit diagram that usually comes with it or an ohm meter can be used to identify these switches. The counter guy won't know how unless he's sharp.

Add a relay. Starter crank wire to pin 85, neutral safety switch wire to pin 86. battery to pin 30, wire from pin 87 to ford solenoid control feed. That way the factory neutral safety switch controls the Ford solenoid power feed.
Doug

I use a starter relay from an early 80s Jeep CJ. It looks just like a ford solenoid but it has a pin that has to be grounded to work, it works great with the stock neutral safety switch. I have mine mounted in the trunk by the battery.

The post that needs grounded is on the bottom side, not visible in this picture.

Mine goes up front in the firewall area near the starter, typically inside the car. Only need to run one 12v cable up from the back.

As CMcAllister wrote, the 4 lug solenoid with the isolated ground for the acivation coil is the one you should have to use the factory ns switch.
It can be tricky to get the correct one based solely on there being 4 terminals as stated. That style solenoid was used on a whole lot of generic equipment. Most used the 12v bypass for ignition, so be aware of that.

And you can get solenoids that look the same, but are intended for intermittent or constant duty. Starters require intermittent style.

Yeah I dug around a little bit and found that NAPA ST83 seems to be the one recommended. It is a AMC/Jeep unit and also used on a lot of boats. The lug on the back hooks up to the NSS and grounds the case in P or N.

I'll order one of them and see how it works. Thanks for the help.

Agreed... well written.

Had to do the same thing on a a friends demon with a ford relay/cut off/CD relay for charge line set up.

The 86 to NSS controls the ground. Turn key all you want when in gear, relay won't work unless trans is in P/N.

Get the cole hersee solenoid. It requires a ground. Thats what I used. Wire the neutral safety wire to the ground side of the solenoid. Works great. It will also last longer than the plastic body solenoids. they eventually wiggle and shake and the body looses its ground through the bracket. I learned that the hard way!

I have been using the Summit Racing® Remote Mount Starter Solenoids SUM-G1750 (basically the jeep solenoid) for years - All I do is put a jumper on the starter solenoid - I have used the transmission neurtral safety switch or the shifter micro switches as the ground circuit for the solenoid. I use this to keep the starter isolated when running