Which Sterter Solenoid?, Looking to remedy the infamous hot-start issue Options

[JDW914]

Hi all! I recently took my first long road trip in my 914 (700 mi round trip out to Peoria, IL to finally pick up a replacement windshield) and while the car performed beautifully, I had my first encounter with what I've learned is the "infamous hot-start issue." Happily I was caravanning and, when unable to find a clear reason as to the car's failing to start after a pit stop for lunch, we tried jumping it, assuming the battery had gone bad, which resulted in enough current to pop the solenoid and start it up. This was necessary a few times during the trip. While it has never caused me trouble before (I've been driving the car pretty regularly for 2 years since its restoration has been "finished") I'd prefer to remove the issue so that it doesn't come back to bite me, especially now that the car has proven itself as such a good road-tripper.

Now in my research since encountering the issue, I've found much documentation of the issue and its solutions, in particular a Ford starter solenoid or a Bosch hot start relay kit. I'd like to go about it with the replacement starter solenoid as this seems a simple and straight-forward enough change-out, however, I've not been able to determine what solenoid it is in particular that will fit into an old VW starter motor. Is there a particular part number or set of models/years that use it, or does Ford have enough standardisation that any old solenoid will work?

Thanks for any enlightenment you can provide!

[ThePaintedMan]

I've often heard them used synonymously, so correct me if I'm wrong. But you guys are talking about a Ford solenoid relay, correct? A solenoid is an mechanical lever that is electronically activated (i.e. the trunk "pop" solenoid"). The relay is an electrical component that helps deliver high power to a given component by way of battery power and a low-power signal, correct?

[stugray]

I've often heard them used synonymously, so correct me if I'm wrong. But you guys are talking about a Ford solenoid relay, correct? A solenoid is an mechanical lever that is electronically activated (i.e. the trunk "pop" solenoid"). The relay is an electrical component that helps deliver high power to a given component by way of battery power and a low-power signal, correct?

Just to totally derail the conversation (but Stus good at that):
Every Electromechanical Relay has a solenoid inside it that actuates the mechanism. A solenoid is just as simple as a steel core with a coil wrapped around it.

What we call the "solenoid" when talking about the starter by itself - is Both a mechanical Solenoid that engages the bendix to push the starter gear against the flywheel AND an electrical Relay that passes current to the starter windings.

SO in a standard setup, the ignition switch (key) carries greater than 9 Amps (IIRC) to engage the starter solenoid and the Starter Solenoid carries the > 65 AMPS to drive the starter.

When we talk about adding the Ford relay it is installed to reduce the > 9 AMps through the Ignition switch down to more manageable levels like 1-2 Amps.

So once you install the Ford relay the system works like this:
Ignition switch passes ~3 AMps to engage Ford Relay
Ford Relay engages passing > 9 Amps to Starter Solenoid
Starter Solenoid engages pressing Bendix against Flywheel AND Passing > 65 AMps to Starter windings spinning the starter.
So it goes Key - > Relay -> Solenoid (Bigger Relay) -> Starter.