Ford Solenoid Hot Start installation instructions, Mark Henry's method Options

[Mark Henry]

Because this comes up so often I decided to make a tutorial on how I install the Ford solenoid.

The Ford solenoid fixes the common hot start problem of Bosch starter solenoid and it also reduces the load on the ignition switch. Although these instructions are for the 914 all aircooled VW's and Porsche often suffer from this problem and with minor changes this can be done to any car.

The issue occurs because the Bosch starter solenoid needs a full 9 volts to kick in. The combination of age, heat, corrosion, many connectors, a small ignition switch and wiring running to the dash and back can degrade the volts to less than the 9V required.
The Ford solenoid only needs about 3 volts for the 12V version and even less for the 6V which for our purpose works no problem.

My installation drills no holes in the car, not a single factory wire is cut, no in-line fuses, fully reversible and simple with no added bullshit.

Please this is not a discussion on if you prefer the wimpy (IMO) Bosch horn relay, want to cut and hack in a new wire or believe throat singing Vajrayana chants is a better method, start you're own thread.

Of course as with any electrical trouble shooting the first order of business is always clean all of your grounds and make sure the chassis to transmission ground strap is in place and in good condition.

I'll start right away with the money shot of the completed installation to show how clean this can be done.

[HalfMoon]

So I've run across a (self created) problem and I wonder if Mark might chime in for a solution?

Previously I had wired in a Ford relay on my sbc converted 914 with a standard alternator per Mark's diagram (an-noted below) as I had been experiencing the well known "hot start" problem.
The fix worked great!
Then I decided to add a track "kill switch" mounted where track workers can get to it in an emergency and therein lies my problem.
When I wire it up per the manufacturer's directions (my diagram below), it works great with one exception...my hot start problem has returned.
Anyone got any idea's?

Marks diagram (an-noted) with no kill switch. Hot start problem solved.


My diagram including addition of a kill switch. Hot start problem returns

[Mark Henry]

So I've run across a (self created) problem and I wonder if Mark might chime in for a solution?

Previously I had wired in a Ford relay on my sbc converted 914 with a standard alternator per Mark's diagram (an-noted below) as I had been experiencing the well known "hot start" problem.
The fix worked great!
Then I decided to add a track "kill switch" mounted where track workers can get to it in an emergency and therein lies my problem.
When I wire it up per the manufacturer's directions (my diagram below), it works great with one exception...my hot start problem has returned.
Anyone got any idea's?

Marks diagram (an-noted) with no kill switch. Hot start problem solved.


My diagram including addition of a kill switch. Hot start problem returns

Right away I can see the battery wired wrong, battery + goes to the starter big post, in your configuration the alternator + wire also goes to the starter big post.

Kill switch shouldn't be wired into the starter, unless it's a battery disconnect, then it should be wired inline on the big battery cable. This needs to have no other wires between the battery + post and the disconnect in. All factory + wires should be after the disconnect out.

Only exception to above is some will run a seperate wire before the disconnect (direct to + post) for the radio clock.

[HalfMoon]

So I've run across a (self created) problem and I wonder if Mark might chime in for a solution?

Previously I had wired in a Ford relay on my sbc converted 914 with a standard alternator per Mark's diagram (an-noted below) as I had been experiencing the well known "hot start" problem.
The fix worked great!
Then I decided to add a track "kill switch" mounted where track workers can get to it in an emergency and therein lies my problem.
When I wire it up per the manufacturer's directions (my diagram below), it works great with one exception...my hot start problem has returned.
Anyone got any idea's?

Marks diagram (an-noted) with no kill switch. Hot start problem solved.


My diagram including addition of a kill switch. Hot start problem returns

Right away I can see the battery wired wrong, battery + goes to the starter big post, in your configuration the alternator + wire also goes to the starter big post.

Kill switch shouldn't be wired into the starter, unless it's a battery disconnect, then it should be wired inline on the big battery cable. This needs to have no other wires between the battery + post and the disconnect in. All factory + wires should be after the disconnect out.

Only exception to above is some will run a seperate wire before the disconnect (direct to + post) for the radio clock.

Thanks for the reply-
Unfortunately, when I ran it with the Alt wire to the to the starter solenoid the kill switch failed to work and would not cut off the running car as it should. The only way I was able to make it work was to connect the Alt. wire to the switched side of the kill switch but then the hot start problem reappeared (either that or a new problem).