Starter Solenoid not working when hot?

[Tom '74 911]

My car is a '74 911 w/a '77 2.7. I've experienced a few non-start issues and thought it could be related to heat and the starter solenoid - I'd love some other opinions though. It seems to occur under 2 scenarios - the first is after a nonstop long drive (like 3-4 hrs. at freeway speeds 75-85 mph) and the second is after getting hot at the track. I've pulled off the highway to get fuel after a long drive a few times and not been able to start it back up, and had the same symptom after the second or third track session of the day - a hot summer day. In all scenarios, I do get power by turning the key to the "on" position, but turning it further to the "start" position yields nothing. It will bump start no problem - which is something I'm getting embarrassed to do in the hot pits! My thought is that the solenoid is getting hot and then malfunctioning. In every case, the next morning, or sometimes even a few hours later, it starts no problem - right up. Other possible culprits I've thought of are the ignition switch itself or a starter relay? (which I'm not sure exists?) I'd love some input.

Also, I looked in the Pelican catalogue, but couldn't find just solenoids - only the full starter/solenoid combo. Can I buy just the solenoid?

Thanks,
Tom

[GH85Carrera]

I had a similar problem on my 85 Carrera. On long trips in the summer it would not start after a good heat soak. As soon as if cooled down a little, it would fire right up.

Just replace the starter. On a 74 it is easy. Do a search for starter on this site. You will find more problems just like yours, and the real solution (for me) was a starter replacement.

[sean m]

Tom,
I've got the same problem after a 2-3 hour trip. From my searching this forum, I understand it's the "fuel accumulator" that's the issue.

I've not replaced mine yet, but it appears a straight forward project. Only problem is cost.....about $125.00 from our host.

Good luck.

[3.2 CAB]

Your solenoid is doing like a lot of older P-cars. It is related to heat, but I have seen many times, if the solenoid does not make any noise at all, it is actually due to the yellow, ignition circuit wire that goes from the ignition switch all the way to the starters solenoid. I had this same problem several years ago. It got to the point, that when I parked the car when I got where I was going, I would always park it where I could let it roll off to start, if it would not start on its own. I finally tracked the cause to the yellow ignition wire. With a cold engine, using a volt meter, it would show 12+volts, but after the engine got to operating temps, it would still show the 12+volts, but when you attempted to crank it, the yellow wire would not carry enough current to actuate the solenoid. I had been told by everyone, that it was a bad starter, bad solenoid, etc. I removed my starter, to bench test, and to open up the solenoid to check the internals(solder iron needed for this) I cleaned the contacts, there was a little bit of sooting on them, I cleaned the contacts with a wire wheel and reassembled my starter, knowing that I "fixed" the problem...WRONG! The next few times, when I would drive it for 45 min. to an hour, then try to start it, the same problem remained. This is when I checked the wiring again, and found the problem being the yellow wire. This is also the same wire that most all after market alarms get tied into for the start circuit kill. It was then I checked the current through the yellow wire, it was great till you tried to actually crank the engine, then the wire would just not supply enough power to the solenoid to actuate. I replaced the entire length of the yellow wire, and have had no further problems like this again. It has been several years now, still OK!! Some will still probably say that you need a new starter or a new solenoid, but get your voltage meter out and check that yellow wire. Good luck!! Tony.

[GH85Carrera]

It certainly can be other things. My starter was the factory original starter with 119,000 miles. It would spin the engine nice and fast in normal conditions. Only on long trips did I ever have a problem. I put a new starter on it last spring before my trip to San Diego. I was careful to park on a hill the 1st couple of times I shut it off. I have not had any problem since I replaced my starter. Even after driving from San Diego to Phoenix. It was well over 100 most of the way. It was nice to feel certain it was going to start. I drove over 4,000 miles and the starter problems are gone on my car.

[glenncof]

3.2 CAB,

I have a 1985 with 187K original miles.

I have intermittent start and measured the yellow wire to be 8.6V at solenoid on original starter pulling 1.7 Amps. I used a short jumper to a battery cable and was still not working.

I had starter rebuilt and there appears to be interference with the starter pinion gear and the flywheel which prevents solenoid from retracting to start the starter motor. I beveled the edges of the worn pinion gear and it worked better but not fully correct.

My next step is to replace pinion gear but my question is:

What voltage do you measure at the yellow wire terminal on solenoid ?

[Tom '74 911]

Thanks for the replies so far - I appreciate it.

Is it possible to replace just the solenoid part of the starter? I could not find such a part in the PP catalogue. The actual cranking mechanism seems fine - it just won't turn over under certain circumstances.

Tony - I will certainly check the yellow wire. That's a seemingly simple fix as my engine and trans. are not in the car at the moment - although nothing ends up being as simple as it seems!

I'm fairly sure it's not the fuel accumulator, as the engine isn't cranking at all.

Is it possible that the ignition switch is at fault?

Thanks,
Tom

[sean m]

Sorry Tony I misunderstood. I read your post again. You get "nothing" when hot.

That's definitely different from mine in that mine turns over when hot, its just tough to start.

Good luck.