On two occasions recently on pulling onto my driveway after a long journey my car won't restart after turning off to unlock the garage door. Luckily I can then just push the car in but with a European tour booked in the summer I'd like to sort the problem.
When I get back in after opening the garage the lights on the dash dim when I turn the key to start but there is no click. 20 minutes later it will start right up. Is this the problem that will be solved by a hot start relay kit or just a good old fashioned sticky solenoid? I'd rather do just the relay or just replace the solenoid so which is it?
Thanks guys

Sometimes it is hard for me to get my head around why things seem to be so hard on these cars sometimes. But the more I read here and accept that we are dealing with 40-year old cars, it gets easier. I am going off me dory here so that is dangerous and some of the more qualified experts may correct me.

But if I remember correctly, the starting circuit carries the voltage needed to engage the solenoid through the key switch. Overtime the switch contacts become corroded and greater resistance is built up in the circuit. So there is not enough voltage going through the circuit when high temps increase the resistance. The installation of a relay solves that. Still may have the sticky solenoid but the problems in the circuit will be fixed by the relay so I think that is you first move.

Orginal Customs sells a really sweet coustom made relay set up for about $30 that is the way to go.

Put the relay in and forget it.

Current Bosch rebuilt starters, at least on this side of the pond, use a solenoid that is cheap and fails easily.

Here's a quick wiring guide.
You should be able to pick up all the parts needed at your local auto parts store.

Might try cleaning your tranny ground strap.
I ended up replacing that ground strap and everything was fine.

The trigger is not pulling too much voltage.
The positive side of the starter goes directly to the battery.
The negative side of the starter relies upon the battery to chassis ground connection and the tranny to chassis ground connection.

That is typically the weak spot as they are old dirty connections.
I also found that over time, while visually it looks fine, the tranny ground strap looses it's ability to move current....just corrosion I suppose, but a new tranny ground strap does wonders for starting.

At the end of the day, and electric motor takes more power to turn when it's hot because things get tighter in there....so it may also be that factor.

Bottom line... The relay is a high current switching device, It will reduce wear on your ignition switch and help with hot start issues.

All modern cars have a starter relay.

Relay, relay, relay. Clean everything till your heart is content but install the relay anyway. A cheap Ford relay is the way to go. Bosch requires 9v nom to operate compared to Ford's 3.9v. + it's a damned sight cheaper.

One other thing is that the current crop of switch replacements are pure CRAP.

We just tried to start a conversion car fitted with a hi-torque starter and new switch and it was a no go ... no power to the solenoid whatsoever. Replaced the switch with the old used one and everything worked as it should.

We should give thanks to OneHungLow for producing crap.

Save the old switches with a relay!

The first year I drove my 914 I had the problem. Old Timer said clean the contacts. Bought a $10 HF dremmel tool, used the pointy sharp file, and the grinders, and went through all the car grounds. Polished all the wire plugs, buffed the ground straps, etc. they all turned from gray to bright brass. Sprayed electronic cleaner and reassembled. Never had a hot start problem again after 3 years. It's a long weekend of fun, but it works. Adding the relay is probably a workable bandaid. Others also say it takes the stress of of the ignition switch. That's the one reason I'll probably add a relay on my next valve adjustment.

In the drawing above....The big fat wire from the battery...you show it going to the plug in with alternator and then down to the relay, or bypass the alternator wire plug and go straight to the relay? Thanks for the I want to be sure clarification.

You leave those wires alone. You will be adding a new red ( + ) wire to the terminal to power the relay at # 30.

Relay it is then.
Thanks all.

Any suggestions for novel/unique/cool ways to mount the Ford relay? ... besides a stainless steel hose clamp around the starter

Screwed mine to the underside of the rear trunk floor (actually drilled thru and welded a fastener from the top (1/4 X 20 or 6mm as I remember).

I tried all the different hot start fixes over the last 28 years, ford relay, bosch relay, rebuilt bosch starters... everything.

Now I don't have a relay on either 914, and never have a hot start issue.

1. I cleaned all the grounds in both cars.
2. I put a new ground cable on them.
3. I use a high torque, aftermarket starter.

The high torque starters spin faster, and use less pull in current for the solenoid.

Technically speaking, electrical current travels on the surface of a wire, not so much through a wire. . cleaning just the trans ground connection isn't good enough if the outside of the wire web of the ground strap is full of corrosion. . Same goes for the positive battery cable. . Often if you peel back some of the insulation at the battery terminal, you'll see the cable is coated with corrosion inside the sheath. . . . all this put together adds resistance and reduces the total current flow available to the starter. . If you have slow cranking then it may be time to replace the cables .
The relay addition is only for the circuit that energizes the solenoid and is good for prolonging the life of the ignition switch. . much easier to change a relay than find a good ignition switch. .

Slow cranking isn't a problem, it's all or nothing. When hot the solenoid didn't move then 20 minutes later it span at a good speed and fired right up

In your first post, you said the lights go dim when trying to crank a hot engine. . this indicates an excessive current draw, which 'should' mean the solenoid is operating and trying to pass current to the starter itself. . It could mean the contacts inside the solenoid have high resistance [lots of pitting] and it becomes 'terminal' when the starter and solenoid get hot. .
IMHO, if this is the case, adding a remote relay is not the correct fix. . all the relay does is place less of a load on the ignition switch itself. The relay is in turn passing the same yellow wire current to the solenoid. .
You can take the solenoid apart and clean up the contacts inside. .

Right, that's my first move as its free!
Then maybe a relay to preserve my switch.

I had the same thing happen to me. Turns out it was a bad connection between the battery lug and the terminal. Terminal was tight but a layer of oxidation had formed between the lug and the terminal.

Car would start, would start, would start, then nothing; all lights dim when trying to start; no headlights. When this happened, with the headlights on, the battery lugs measured 12.6V and the terminals measured about 4V.

Took the terminals off and cleaned everything. Never had a problem after that.

This is exactly why replacing the 40 year old tranny ground strap is critical...along with a new positive lead.

Clean clean clean.

But go for it, if you want to spend the money and time for a relay, have at it.
You will still need to replace the tranny ground strap.

A relay is not necessary, however, if one is not used, you will have to replace your ignition switch sooner than you should have to. Why? A simple test will explain all, even to the electrically challenged!
Find an old starter that has a good solenoid. Hook it up to a battery using nice clean new spade lugs. Hook up the negative to negative battery post , then touch the new spade lug to positive battery post. The solenoid should energize. Now remove the spade lug from the positive battery post. See the nice spark? Now look at the spade lug where it came into contact with the battery positive. See the black mark? That is what happens to the contacts in your ignition switch every time you start your car! Carbon from the arc flash. If you had a powerful magnifying glass and looked at the spade lug, you would see pitting also. Now if you have a bosch relay, do the same test. Arc is so small it can't be seen. Relay contacts are engineered from a viewpoint to extend the contact life by using special allows that resist pitting and arcing.
A relay , if and when it fails, is much easier to change that the ignition switch. I have been using this relay for years without a failure. Cost about $2.00. While this one is Chinese, there are others out there that will work just as well.
Tom

Installing ford relays since the eighties. I've never replaced a switch or hacked a harness yet.

That is not really true.
AC current moves across the surface of a conductor. DC current moves through the entire bulk of the conductor. (Google "skin effect")



And another thing that makes the arcs worse is the reverse EMF voltage spike from the magnetic field in the solenoid collapsing when you open the switch. That makes the arcs even bigger.

Certain relays have a "reverse EMF diode" in them to dissipate this spark. They are also called "snubber diodes". They reduce the effect of the reverse spike.



Good site about relays:
relays

The inductive spike is what makes the arc and carbon build up. The tiny spark from a relay that draws 150 Mili amps is really small compared to the arc from the 35 amps the solenoid draws. To determine the voltage, use V=IxR, where the resistance of the opened contact is meg ohms. 35/0.150 = 233.3. So the spark from the solenoid is going to be 233.3 times as bad to the contacts.
The switch is only going to have so many of these events before the carbon build up or surface damage from pitting causes a high enough resistant connection in the key switch and the solenoid no longer operates, then either a relay is needed or the switch requires replacement. Installing a relay will prevent early switch replacement.
I have done this test several times to convince others of the reason switches fail and if I had a camera that would take video, I would post one here. It is eye opening!!
Tom

Solid state relays is the way to go.

Tom,

That is a pretty good explanation. The technical explanation is that the current through an inductor (starter solenoid) cannot change instantaneously.
So when the switch is closed and ~35 Amps is flowing, then you open the switch (resistance goes to infinity), the current cannot stop flowing, so the voltage climbs to infinity to try to maintain the current flow until it reaches the breakdown voltage of the air gap (10,000 volts or better) before it arcs across.
This is exactly how the points & coil make the spark jump the plug gap and the gap inside the rotor.

The diode inside the relay in the picture above gives the current someplace to go so the voltage doesnt try to climb to keep the current flowing until it dissipates.



A SSR would work, but it has to be the kind that can allow "avalanche breakdown" to dissipate the Reverse EMF or it will fail quickly. (that just means it keeps flowing current even after told to turn off).
The electronic ignition a lot of us use to replace the points is technically a SSR.

stugray,
You are correct, I was trying not to get too technical as most wouldn't understand unless they had an advanced understanding of electricity. The current applied takes 5 tau to reach maximum effect and the same thing happens upon switch opening. It takes 5 tau to completely discharge the voltage from the collapsing field.
This arc is just like a welding arc, only in the welding arc, current and voltage are increased to maintain the arc to completely melt the metals being welded.
I have explained this several times in the past several years, but some just don't believe it. Why I don't know. Then again, some don't believe that fuses are necessary to protect circuits either. ????
Tom

I believe it and understand it. That's the same reason a condenser (aka capacitor) was put in place in parallel with the points. It gives the voltage spike a path to ground that is less resistance than the air gap between the points. Kinda like a catch can for the spark.

I don't have training in analog electronics, just digital. But I have read the basics.

So why not put a capacitor at the back of the ignition switch? It would be cheaper, it would dampen the electrical spike, and it would not add another circuit to the car like a relay does.

Why make it more complicated than it is.

I can install a Ford relay in 30 minutes, that includes making the harness.
I cut no wires in the harness.
I drill no holes*.

*I make one hole on the solenoid bigger 10mm, then carefully bend the bracket and it bolts to the bottom starter stud.

The only one ford solinoid I've had fail in almost 30 years was in a winter driven Super Beetle. The solenoid was totally corroded from salt. The car was scrapped a short time after a new one was installed. (In fact that very replacement is now on my bus.)

Clay,
A capacitor would not do the trick for this application. A diode of the proper size would, although I don't know what size would work. Something in the 600 volt 5amp range may do the job. I'll check my parts to see what I have and give it a test. A capacitor/condenser is basically like an accumulator in a fluid system in that it tries to tone down spikes in the supply voltage. A diode is the preferred way to suppress the inductive spike.
The capacitor for the ignition system does more than just keeping the arc down for the points. It gets charged up and helps on the next closed point charging of the coil. It also helps the collapsing field collapse faster upon points opening to provide a stronger spark. If the points are arcing, current is still flowing thru the coil. If current is still flowing, the field can not collapse, and won't allow the strong spark out of the coil secondary. If you are interested look up kettering (sp?) ignition system. It explains in pretty good detail why the condenser is needed for the points style ignition system.
tom

Very interesting! Thanks for posting.

Hey Tom, since many of the components are getting built to lower and lower quality standards, I can't help but wonder if a stock condenser might be a bad choice. Maybe a quality capacitor instead? Or is it one of those things where even the crappiest part will successfully do the job?

Like I said, I have training in Digital electronics. I never did the whole analog thing, but I understand the basics enough to troubleshoot issues with wiring in cars. Thanks for the info. I learned something today.

Wow! This is what I love and hate about this site. I wish everyone would agree on one solution/theory on my question yet love reading the debate when it's someone else's problem.
I'm going to refurb my existing old, good starter solenoid to solve the hot start problem and fit a relay to help prevent further damage to my ignition switch. I will also replace my transmission earth (ground) strap just because it comes up in so many threads I read on here.
Thank you and goodnight!!

What

Your not going to solder in the capacitor as well????

Well, I looked thru my limited left over parts and the only diode I had left was a !N4003, 200volt 1 Amp. Hooked up a test for it and noticed no suppression of the arc. Did some research and found out something. The diode used to suppress the inductive spike needs to be 10 times the working voltage of the circuit and at least the same current capacity of the circuit. So I need at least a 120 volt 30 or so amp diode to be effective. I will keep looking and if I find something reasonable close, I will get it and test it and let every one know the results.
McMark,
Are you referring to the condenser for the ignition? Those seem to be doing the job fine. A capacitor just won't work to suppress the inductive spike for an inductor.
Mark Henry,
It's progress. If something new will work better than a solution that has been around for decades, why not use it?
Anything solid state will out last a mechanical device just because of the mechanical wear over time of the mechanical device. Look at how much better solid state ignitions are than points/condenser! I am just trying to improve the reliability of the starter circuit, not condemn the use of a Ford relay.
Tom

You just stayed at a holiday inn

With full light effects and adjustable power settings, the Flux Capacitor powers the 1.21 jigowatt-controlling heart of the 914starter.

Tom...humour ar ar

Nanu Nanu ..................

You have to admit... installing the "helper" relay to drive the solenoid is kind of funny since the solenoid is a relay itself:

12V 12V 12V
| | |
Ign Switch -> Relay -> Relay -> Starter


Hmm... my whitespace in the lines above doesnt show up.
Anyway I was trying to show that a separate 12V source feeds each relay in that chain

Not really, the Bosch solenoid takes a full 9V to make it open. When the car was new, or in it's expected life of less than 10 years, the stock system has no problem with this.
The ford solenoid takes less than 3V to open, giving a full 12V to the Bosch solenoid, causing way less "strain" on the system.
You can't just replace the Bosch solenoid as it also has the bendex.

This fix has been around since the 70's, on the bug maybe even the 60's, it's not rocket science.

Actually the normal state of the relay is open, and when power is applied, it closes.
Minor point, but could confuse some new person.
I spent a good deal of time thinking about the diode remedy to suppress the inductive spike from the solenoid. I do believe the correct size diode would work, however, how would one know it is still working a week/month/year later? You wouldn't, until suddenly you have a start issue and find out during troubleshooting that the problem was the diode had failed. With the relay, if it fails, you know right away. So I think the relay remedy is the best all around fix in this case.
There are many different relays that will do the job. For whatever it is worth, I prefer one of the Bosch style as it requires no tools to replace one in an emergency. Just unplug the spade lugs from the old one and plug them into the new one. 2 minutes and a zip tie and you're back on the road. You can finish the installation when you get home.
Tom

VW/Porsche built up a lot of good karma by bringing out the 914. Since then a little bad karma has been chipping away...


1 Shoulda had fender liners.
2 Shoulda had cable shifters. (Well, okay, but they could have invented them!)
3 Shoulda had a starter switch relay.
4 Shoulda had better window/top seals.
5 Should NOT have quit making them! (That was the worst offence!!!)

So, okay everybody, next time you are in there/under there, clean all the connectors and grounds, replace the ground straps and battery leads, add a relay to save your ignition switch. Yours and mine, now, are working fine, but do this and it will for the next guy too, in, say...2050 or so. Good karma. And a good excuse to crawl under your/my car that is 95%donesoIcanputoffworkingonitsomemore.

PS very good and informative discussion...