So this issue has happened 3x now in the past few months, and now today after driving 300 miles up to Brevard, NC on the way , stopped to get gas, going to start it, no crank. all other electronics work, fuel pump priming just no starter engagement. it’s happened cold too, i can get it to start by push start.. so about an hour ago i pulled the steering wheel and replaced the plastic switch still no starter , i also checked the yellow wires under passenger seat (seat buzzer by-pass) , i don’t think that’s the issue.

I bought and installed a new Bosch starter about 6 months ago and installed it on this newer motor a few months back, so now i am wondering if it’s a bad solenoid? wond not crank . the last time it happened was a months ago, push start got me home from the store, and when i got home and pulled into the garage after turning it off it started right back up and has for the next 10 times —- until tonight.

what are the other possibilities? does the power go from the ignition switch to the relay board and then to the starter? i have done a few searches , but looking for someone that’s maybe had this issue or understands the whole schematic better . i don’t have a multimeter with me but i can get one tomorrow at O’Reilly’s and i might see if they can get a starter., i’m just guessing and grasping at straws ..

- oh, for those that don’t know it’s a ‘75 2056 d-jet.

Phil

Check the female spade-yellow wire- on the solenoid for good contact next time. That was a problem on my 76. When you turn the key to the start position does your amp gauge drop? Do you hear any clicks when turning the key?

i will recheck the yellow spade connector.
when turning the key to the first position everything powers up, when turning to start position you can tell there is a dimming , i didn’t look at the volt meter seems there is current flow , as i turns the key all the way also the fuel pump is priming so there is some kind of signal being sent, it’s getting to the ecu ans FI just not the starter, not sure if i’m hearing any click.

Use screwdriver to short between the 12v positive battery & starter solenoid lug (8mm threaded terminal) and the solenoid (yellow) spade terminal that is on the solenoid. Car in neutral, parking brake applied, ignition off (so that it doesn’t start while you’re under the car) be safe - be careful. If the car is left in gear, it will move when the starter begins cranking.

If the solenoid engages and it cranks - you know know you have a problem getting enough voltage and current through the yellow wire to activate the solenoid.

If it doesn’t crank you have a problem in the starter and/or solenoid itself. Check for proper ground between the transmission and the body. If that ground is good, the problem is defiantly in the starter & solenoid assembly.

With the system 1/2 split like that you now know where to focus the rest of the troubleshooting.

And the ford solenoid fix is so easy it's fun. I had this issue intermittently as well till I did the fix. If you can jump it with a screwdriver, than the solenoid is what you need.

Will the car push-start ?

If you have a degraded signal coming to the solenoid engagement spade a common Bosch relay has been my go-to for years.

Adding a Ford solenoid is the same fix but that Ford solenoid needs 3 amps to trigger.
A Bosch relay needs 0.3 amps to trigger and can supply 30-40 amps if needed.

Modern cars all have a starter relay and the OEMs are no-longer running solenoid power through the ignition switch.

Seeing power at the small line to the starter but that power is not enough to trip the starter, add direct power (bump switch, screw driver).
Starter works?
Add relay.
30 comes from large bat term at starter, 87 goes to start solenoid connection (small spade on starter). 85 is signal from ignition switch and 86 is your relay ground.

Works great and if you're smart on the 85 lead you add a second wire to and put that somewhere in the engine compartment to allow easy connection of a bump starter lead...

Ford solenoid is nothing more than a BIG relay that can supply 300+ amps and drive the entire starter. The Bosch fix cannot drive an entire starter, but it can easily drive a starter solenoid like our 914s have.

It's not a bad idea to also add an inline 15-amp fuse before the Bosch relay in the 30 leg to protect it from a grounded solenoid.

Bosch Brazilian solenoids last about 6 months, that’s what they use for all rebuilt units, I went to the hi torq Toyota starter about 2 years ago, no problem whatsoever, very simple to rebuild too.

if the car will not engage the starter when hot and you have a new bosch starter, first check the yellow lead at the solenoid for power and then check for voltage. If the voltage is down you can install a wr1 bosch relay kit. Also check the neg battery to firewall ground and the trans rear cover to bottom of the trunk floor ground

do you know part # for the toyota starter? i just checked with local Flaps and i can have a 914 bosch starter here from them at 3pm- i’ll try the screw driver trick for dx after this show is complete
some beautiful cars here today! over 350 porchche only 2 914’s!

doc,
i checked the grounds the are good, we’re all new too, but rechecked just in case. i have to get a multimeter and can check, it’s a new motor and i know the stock volt meter shows 13-14v running.
could anything at the relay board cause this? or just the solenoid?

Phil

1/2 split - don’t guess randomly

If you want to PM me I’ll give you my phone #

yellow wire under the passenger seat...
Is it still going through the "logic circuit" box under the seat?
If yes, I would strongly suggest you remove the two yellow wires and directly connect them.

Grounds, go to the parts store and get yourself a 36-40" ground cable, with bolt tabs (female) on both ends.
Bolt on end to the large upper starter bolts that physically bolt the starter to the transmission.

Bolt the other end to the negative terminal at the battery at the bolt that tightens the battery terminal.
Leave the battery terminal connected to the normal body mount so everything else works.

Remove any doubt with this method.
If it solves it, you need a new ground strap.

I have built a starter button for testing things...and hotwiring cars from the engine bay.
Its simply a 30amp push button switch with two long leads.
One goes on the battery positive terminal, the other goes on the starter at the little lead (yellow wire) terminal.

Side of the road, scary yet effective.
Use a quarter... (ed showed me this) and in neutral..get under the car on the drivers side.
Use a quarter to touch the large positive terminal on the starter to the yellow wire terminal at the starter.
Car will start.
Neutral....ebrake on (or block the wheels)

This shows you if the starter itself may be at fault when hot.
If it works fine with the hand held switch, you have wiring issues.
If it does not work..you have a starter issue.

If you add the ground strap as I have described (do it how I am describing) and your starter works when hot...you have a ground strap issue.

Eliminate the issue of heat creating resistance by going all the way around the stock wiring in both cases to determine where the issue may be.

I am a fan of the aftermarket relay to help eliminate the issue, but if you fix the root cause, the relay is more of a way to protect the NLA ignition switch from melting.

the OEM design is running something like 20 amps (now 30 amps) from the battery, up through the ignition switch (failure point) back down under the passenger seat to that "logic circuit" (failure point) and out to the starter.

the logic circuit is all designed so you cannot start the car if the seat belts are not engaged, and it fails.
Thus, wire around it.

the old wiring we have gets corroded inside, thus can no longer move 20 amps...and the starter may pull 30+ amps...which can Melt the wire somewhere you cannot see, or melt the ignition switch.

Method 1) add relay at starter location that now moves the 20 amps through new wires, directly from the battery to the relay. Use the stock yellow wire to trigger it (now 1-3 amps)
Method 2) replace the chassis ground solution (again..30 amps now) with a direct connect ground strap from the battery to the starter body.

These two methods are cheaper/easier (arguable) than fixing it properly.
Fixing it properly may be a new wiring harness, eliminate the logic circuit , and a brand new ground strap between the transmission and the chassis (and clean the ground from battery to chassis)


Rich

I’m sorry to have to point this out, but a circuit that was previously designed to draw 20A (as in example) will not suddenly draw 30A due to an increase in wiring resistance increasing from corrosion. This is physically impossible as dictated by Ohms Law.


However, I’m in rabid agreement with Rich’s suggestion to 1/2 split the system by basically hot wiring the starter B+ to the yellow solenoid control. Whether you do that with a screwdriver or a remote starter switch doesn’t make a bit of difference in the end. You then know if the problem is in the starter solenoid assembly or in the wiring and can focus on the appropriate solution.

I'm a huge fan of extra grounds as well.

I rebuilt a 1979 Fiat X19 for my wife and during the rebuild I added extra grounds like a mad man.

The 1979 X19 might be the all-time WORST electrical system in a Fiat.

That car went 85K without a single electrical failure after adding all the grounds.

The current thinking (pun intended ) has electrons traveling from the negative to the positive side and so our grounds are really the power supply.

On an old sports car I will leave that extra wire from terminal 86 on that relay somewhere accessible as to NOT have to crawl up under my 914 with a quarter.

That type of crap only happens in the rain, in a mud puddle, at the side of a busy road for me...

This is why contribute our suggestions in the forum to help others correct us.
Its also why (DM me or give me a call) is not the way to help others.

a 20 amp circuit design will indeed melt wires that are designed to support 20 amps.
I do understand ohms law...but I was trying to explain things in a public forum , of non electrical engineers, to help.

Happy to hear criticism, but I am also quite comfortable in my own skin to help others in a public forum, so others can refine the answer and create a positive outcome.

Rich

At a car show..in the rain, in front of others...after a few...with NO tools on hand.
But...Ed always has a quarter in his pocket.

Yah...but that is why we love old cars.

rich

As am I. So let’s help others by understanding what is going on.

So let’s be clear that a circuit designed to pull 20A will not melt when pulling 20A through good wire. It can actually melt when pulling LESS than 20A through degraded wiring.

How?

Let’s start with ohms law and a 12v system

To draw 20A, how much resistance was in the circuit as designed?
12v / 20A = 0.6 ohms of resistance
This 0.6 ohms of resistance would represent normal solenoid resistance + the wiring resistance which should be almost, but not quite equal to 0.

So now let’s say the wiring has corroded and increased to 0.5 ohms of resistance by itself. We now have a circuit with 0.5 ohms of wiring resistance + 0.6 ohms of solenoid resistance. This is 1.1 ohms of total resistance.

So how much current will we pull?

12v / 1.1 ohms = 10.9A

Circuit is now unable to pull full current. In fact, it is only pulling slightly more than 1/2 of the design current. So if in this example, the solenoid needs 20A of current to operate the solenoid, it can’t pull that current and the starter solenoid won’t energise properly. This will be true regardless of how many grounds are attached to the solenoid.

So why does the wiring melt when pulling less than 20A it was designed to pull?

The power (I.e heat) the circuit has to to dissipate is Power = current ^2 (squared) * Resistance

When wiring is near 0 ohms, there is no heat created . This is the design condition of healthy wire.

But we have 0.5 ohms of resistance, internal to the wire, created by corrosion.

So how much power (heat) will be created by pullling that 10.9A though the corroded wire?

Power =10.9A * 10.9A * 0.5 ohms
Power = 59 watts

So now we are asking a wire to dissipate 59 watts of heat. Remembering that it was not designed to do this. 59 watts may not sound like much but it is quite a bit. Trying to pick up a 10 watt ceramic resistor that is operating normally will be quite hot to the touch and uncomfortable to hold. We are talking about roughly 6 times hotter.

So this is how wiring melts from corrosion while actually pulling LESS current than what the circuit was originally designed for.

Did I mention the ford solenoid is a fun and easy job?

https://sierramadrecollection.com/products/...2e-65-89-p19925

i used the screw driver trick, and right after that i did start… once , then not again. picked up a new starter ans solenoid from O’Rielly’s , took it out to a local guy’s shop and installed it,
all good, so i guess some of these newer solenoids don’t last long. .
i will look into the ford solenoid or maybe the toyota hi torque options, but for now i have one thst should last a while, if not , it’s lifetime warranty should last a while.

Rebuilt isn’t what it used to be. Glad you got it down to a confirmation that the problem was in the starter itself. Great job!

In So Cal, Oscar's on 17th Street in Costa Mesa will rebuilt your starter or alternator. Good prices and fast turn arounds

yea, and the one that failed on me i didn’t buy from a chain, this one i got from O’Reilly’s so national chain lifetime warranty. i might get a spare solenoid to carry, add it to the collection of other extra parts i keep in the frunk. i just didn’t really believe it would be the starter. i was so sure it was the ignition switch i had ordered a couple a small briny it with just in case this again happened, even had the tools. as you all know pretty hard to get under a 914 without a jack or lift. got to live the Porsche community!!!

nice shop , more of a “garage mahal”
a recently acquired 912e, a 1975 911 targa with some type of 959 fiberglass body conversion and some Harley knuckle heads, a 1940’s Lincoln and a beautiful TR6,

Been under there more times than I care to count.

Worst was on a date once and had to do the screwdriver trick. Turns out she was rather impressed that I knew how to do something useful and kept us from being stranded . . . So not all bad.

Glad you’re back on the road and not stranded or push starting!

Wow! Dream garage!