starter motor issue

[Alan L]

I am looking for ideas to solve the following problem.
My track car (930) will not fire the starter motor when heat soaked. Turn the key and nothing happens. When it is cold, this is not a problem. But after a race, it happens more than not, til the engine cools well down. I have pulled the starter and solenoid apart twice, can find no faults and of course they bench test OK every time. I finally wired a loop into the key/solenoid circuit, with a light bulb in the loop, by the gear lever. When the issue happened again, the light was not on - ie no power to the solenoid. The only thing I could think of was the ignition switch, so I swapped a new back into my switch (not easy). But as of last w/end racing, it has done it again. Don't know where else to look?
Thanks
Alan

[DRACO A5OG]

DOes alt light go on after it heats up prior to trying to start?

[mpetry]

I have had this exact problem on other cars, P-car and not. I suggest you need a starter relay so that the starting current does not go thru the keyswitch.

The other thing you could do is install one of those "high torque" IMI starters, available from our host - about $200. I have one in my SC and it is fantastic.

Assuming your grounds are all good and the battery strong, this is the fix.

[Alan L]

Thanks guys. Yes Alt light is on - all the dash looks normal. But when you turn the key, the alt light does dim a bit. Yes, a relay may be the answer - for some weird reason, maybe the solenoid draws too much load thru the key switch terminals?
I am completely baffled by this one.
Maybe the heat soaked starter is drawing a lot more load than normal, and maybe too much for the key terminal. I should say this last w/end it performed faultlessly and I thought I had it licked. We even had one race red flagged (1 lap in), then re started on the track, and the engine fired up fine.
THEN, I went to put it on the trailer after sitting 15 mins after last race - no go. Had to tow start it. Until then I would have told you I had it licked. So I am thinking the key switch terminals are the issue?
But the starter load doesn't go thru the key switch - right? Only the solenoid load? But maybe that is too high when really hot?
Alan

[Alan L]

[QUOTE=mpetry;7265345]I have had this exact problem on other cars, P-car and not. I suggest you need a starter relay so that the starting current does not go thru the keyswitch.

QUOTE]

PS - I had a VW that did this too me about 30 yrs ago too.
Never figured it out - used to have to crawl underneath with a bit of jumper wire across the solenoid/starter (and hope I hadn't left it in gear ;-). 930 a bit low to crawl under.

Alan

[911-detroit]

My very first thought was it's hot,metal expansion. Grounds simple answer. Second would be contacts, not uncommon issue with distributor or on ignition switch. This happened on a Volkswagen only when hot,turned out to be faulty starter, I discovered this when I by-passed starter circuit and jump wired starter directly.

[mpetry]

a bit of jumper wire across the solenoid/starter

Yes, that's what the relay does - the high current goes straight to the starter and does not run thru the keyswitch. This was the classic VW fix back in the day - somehwhere I have a pic from the old John Muir book "How to keep your bug alive"



You can make your own for about 15 bucks. The Ford relay is just a big beefy relay. Note the connections.

I believe our host also offers a kit for about 25.

If you want a pic of a built set up like this with Bosch relay let me know and I'll post a pic

[Alan L]

So, where would you insert the relay Mark?
Since I don't seem to be getting power TO the solenoid when this happens, I'm guessing it should go between the ign switch and solenoid - so the solenoid can draw power direct from the battery, rather than thru the switch?
Thanks
Alan

[mpetry]

I had to study the diagram carefully. The relay is a remote switch at the starter that draws the current directly from the battery.

The control wire switches on the relay switches that current on and off. The high current is not going thru the keyswitch.

[Alan L]

OK,got it - many thanks - for some reason your pic did not come up on the initial post I got.
I'll try that.
I always figured the ign switch was only carrying current load to the solenoid windings and all the battery/starter load went directly across the terminals at the end of the solenoid. Is this not correct?
Alan

[OsoMoore]

Originally Posted by mpetry

Yes, that's what the relay does - the high current goes straight to the starter and does not run thru the keyswitch. This was the classic VW fix back in the day - somehwhere I have a pic from the old John Muir book "How to keep your bug alive"



You can make your own for about 15 bucks. The Ford relay is just a big beefy relay. Note the connections.

I believe our host also offers a kit for about 25.

If you want a pic of a built set up like this with Bosch relay let me know and I'll post a pic

The John Muir book was amazing - we had 4+ VW Golfs growing up and we each bought a copy for doing repairs.

[Alan L]

Wow, great art work. Is that the front cover?
Alan

[Alan L]

"Good" news. It now won't start when cold . So, I have a fault I can hopefully trace. When I turn the key the Ign/Alt light dims. And there is a relay clicking. I have traced the relay to the fuse panel. It is next to my fuel pump relays. But I cannot find a relay in that part of the circuit diagram - so a bit stumped at moment. Swapped the relay out, made no difference. The relay is functioning and sending current somewhere (getting warm). just not to the solenoid. I shall continue. Hopefully it stays dead so I can trace it.
Alan

[DRACO A5OG]

Alan,

I have iginition issues, found the culprit to be my electronic part of the switch, try grabbing the back of the swtich and see if it moves around?

The Track enviromnet is harsh in vibration so I think it may dislodge just enough if there is a solder joint crack it will be significant to cause a fault.

Today,I was on some rough roads and when I got back into start her, I got all lights and fuel pump working and solenoid click but no start. Grabbed the back of the switch and found it to be dislodged a bit, pushed her back in, VOILA, Voroom

I have a new switch sitting on the shelf, but I don't worry about it since I can get her to start right after a no start, push back of the switch, Good to Go.

Jim

[Alan L]

Thanks Jim - I will check that too.
Correct about track being harsh environment. Just found I am missing a tranny mount bolt. Shook it right out. It will have happened when I had a 'bad' start and lots of clutch shudder/wheel spin.
I checked if I had power at the solenoid terminal end. This time I did.
So I jumped the solenoid and it worked. Put the lead back on and now it works again.
Go figure.
No wonder these things are hard to track down. But I think I'll put a relay in from the switch anyhow - can't hurt.
Regards
Alan

[DRACO A5OG]

Alan L,

Check your "positive cable to starter" post, I was about to swap my ignition switch today but when I tested the new switch, FAIL. WTD???

So I started trouble shooting:

12.87 at battery,
All terminals clean and tight
9.4 volts at Solenoid
12 Volts at Starter.

WTD? per bentley Starter Fault, but wait I just refurbed it, oh poop thank goodness it is under warranty.

I started to remove the starter then noticed the battery via cable to starter "POST" was loose. I tightened it.

VOILA, there was the littler culprit. She started right up, no jiggling the switch doo doo.

Jim

I was thinking about your and thought maybe it was the same issue, without removing the cable, you can not tell. once removed it was quite apparent, here was my open circuit.

[Alan L]

Yes, Jim, good thought - definitely a possibility - especially on a track car suffering severe vibration regularly.
So, now my plan is to throw everything at it - install relay from ignition switch to take load off the switch terminal, going to pull the solenoid apart - again - and see if there is any possibility it is jamming when hot or vibrated, and like you suggest - make sure I have secure voltage at the starter - although in this case, I am sure it is lack of action on the solenoid that is the issue. But of course this may be due to lack of voltage too.
regards
Alan