On a previous 914 I had many years ago I experienced a "no crank" condition that I traced back to my ignition switch. It seems that in the start circuit on the switch, when the key is released a tiny "backfeed" of current from the starter solenoid arcs across the terminals on the ignition switch, and over time damages the contacts.
After a little research I determined there are two ways to stop this "current backfeed", one is to install a diode to ground in the starter wire, another (which I did) was to install a simple 5 pin relay.
Click to view attachment Click to view attachment Hope this is of some help, please disregard or delete if this has been discussed before.

Please pass some popcorn...

EDIT: http://www.914world.com/bbs2/index.php?act...2Bstarter+relay

Whoosh, right over my head

A guy goes to prison for the first time, gets walked into his cell in the middle of a long cellblock. The cellblock is mostly quiet, not much going on.

The silence is suddenly broken when someone in the cellblock yells, "58!" and the place breaks out in laughter. Then it's quiet again.

A few minutes later someone yells out "143!" and the place laughs again. Then more silence.

A few minutes after that someone yells "24!" and the place roars in laughter and someone says "Yup, that's a good one". Then more silence.

The new guy taps on the wall and whispers to the guy next to him, "hey, what's what all about, calling out numbers?"

Guy next door says, "oh, we've all been here so long that we numbered the jokes, and we just call out the number when we want to tell the joke."

"OK", the guy thinks to himself. "I'll give it a shot" and he yells out "75!"

Silence.

New guy taps on the wall and says, "hey, what happened? Why is no one laughing?"

Guy next door replies, "you didn't tell the joke right."

It's not you. The topic of adding that relay to the starter circuit has been an ongoing point of contention for years on this forum. Some say it is necessary. Some say it is not. Some say put in a Ford starter relay. Some say to use a gear drive starter.

So go back and read some of the links in that search you were sent.

And welcome to 914World.

And yet no modern car is without a relay and most have a diode or similar as well, which protects the relay contacts. Even the relay coil gets a diode to minimize the wear on the key switch.
Common practice that began in the electronics industry and then moved to the automotive.

Takes ten minutes to put in the ford solenoid with zero damage to your car and costs 20 bucks or less. Don't let the other inmates scare you.

I sold a rebuilt starter to a guy about a year ago. He calked saying he thought the starter was now gone bad. Turns out the Ford solinoid he added had gone bad and only outputting 7 volts.

Someone tell me why the Ford solenoid (relay) is superior than the smaller Bosch 5 pin relay

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Typical Bosch aftermarket automotive relay is rated 30A. The generic Ford starter relay is rated for 150A or a little more depending on who’s making and rating them.

Starter solenoid draws around 25A nominal at 75F ambient temp.

That’s not a lot of margin in the Bosch relay. The standard Bosch 30A automotive relay doesn’t have an integrated flyback (freewheeling) diode. Bosch requires that diode on an inductive load (i.e. solenoid) in order to achieve their rated life cycle for the relay. As mentioned previously the lack of a flyback diode will lead to burned relay contacts that eventually malfunction. Note: the Ford solenoid doesn’t have an integrated diode either which is why those can malfunction too despite the much higher current rating.

I measured the starter solenoid current draw a while back using a 50A, 75mV shunt resistor. This was on a properly operating starter. My bet is that solenoid draw is even higher in cold weather. I’d also bet there are a statistical population of solenoids out there that draw more current than my random sample of one.

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I have yet to see anyone install a proper flyback diode in parallel with the solenoid load on either a Ford or a Bosch solenoid install.

Flyback voltage can be very high (hundreds to thousands of volts). Even though it only occurs for milliseconds, the arching can eventually burn contacts regardless of the Bosch or Ford steady state current rating.

Easy. Cheap. Fast. Perfect 914 solution. Not one problem since doing it. Instructions from a Mark Henry thread. (Haven’t seen him posting for quite a while. Deceased?)

I didn’t think the 914 relay would draw that much current, so you’re saying the Bosch 5pin relay was really “right on the edge” as far as having the capacity to actuate the starter coil.
I have a couple of non-Bosch 5 pin relays that are rated 40 amp and have seen some for sale rated 50 amp.

I have a solenoid in my FordClick to view attachment

Life is good huh george?

Why is there no rock behind the back tire?

347... Diode explanation on YouTube.

https://www.youtube.com/watch?v=bvDuyM2e4gw&t=347s

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Nice video. Way to simple of an explanation.

I would have just said
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Not needed as the Solenoid got fried and welded the Bendix to the flywheel?

Gorgeous. Stunning. If that's a F40, my neighbor had one. His was white. I tried to buy one once, but the guy didn't accept my offer of 250,000 pesos.

So George, when are you going to buy a decent car?

This looks about right. Ohm's Law where inductance & capacitance are the complex part of resistance. These are the "i" or (-1)^1/2 components. Is there a dependence upon the size &/or rise time of the inductor? Just curious.