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Kirkham Motorsports

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  • 1 Post By pormgb
  • 1 Post By Tommy

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  #1 (permalink)  
Old 06-10-2017, 09:16 AM
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Cobra Make, Engine: SPF Coupe #136, 427SR FI
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Default Starter does not activate once in a while

Hey Gang

Need some wisdom please...here's the scenario. This has happened twice in about 400 miles (6-8 weeks apart) and the exact same scenario.

Drive about 10-15 miles. Car is at full operating temperatures.
Pull into get gas (yes on both occasions)
After filling up hit the switch and nothing from the starter. No noise, no click, no nothing...silent. When I hit the switch I see the lights dim a pinch so I know it is sending current to the starter.
All other electrical functions properly.
The volt meter at this moment reads like 9 volts.
Let sit. First time was 15 minutes. Today was 10 minutes.
Fires right up.

Here's what I have done:

After the first occurrence got a new battery.
Tested the alternator - tested fine.
After today check the power and ground cables. Cleaned ends all good.
Went out for another ride today (only difference didnt stop at a gas station) got her good and hot and restarted MANY times just fine.
While driving the volt meter shows 14 +/-

Any thoughts on next steps (beside not going to gas stations...hehe)?

Thanks in advance.

Jeff
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  #2 (permalink)  
Old 06-10-2017, 09:48 AM
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I had a similar problem on my LS6 swapped Porsche 944, the starter would not turn after the car reached its full temperature then sat for a few minutes, if I drove the car hot then restarted it, it would start right up. Since you are seeing a power drain, power is getting to the starter, it sucking almost all available amps.

My issue was related to the close proximity of my starter to the exhaust headers and the stock starter could not handle the heat, I think it was heat soak why it would not turn once the car sat for a few minutes.

I replaced the stock starter with a high torque gear reduction starter and the problem went away, I also use a high torque starter the 352 in my Cobra.
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Old 06-11-2017, 02:51 AM
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Quote:
Originally Posted by pormgb View Post
I had a similar problem on my LS6 swapped Porsche 944, the starter would not turn after the car reached its full temperature then sat for a few minutes, if I drove the car hot then restarted it, it would start right up. Since you are seeing a power drain, power is getting to the starter, it sucking almost all available amps.

My issue was related to the close proximity of my starter to the exhaust headers and the stock starter could not handle the heat, I think it was heat soak why it would not turn once the car sat for a few minutes.

I replaced the stock starter with a high torque gear reduction starter and the problem went away, I also use a high torque starter the 352 in my Cobra.
THanks!

The other possibility I just thought of is the clutch depression switch which only allows the car to start when the clutch is fully depressed. Although it is not located in an area subjected to major heat (if that was the case it would also impact the brake light switch as they are co-located) it is a link in the starter circuit. I will run a jump wire in the event it happens again and I can easy jump the circuit to diagnose if that is causing the problem.

THanks

Jeff
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Old 06-11-2017, 04:08 AM
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This can be hard to diagnose if it only happens occasionally, but here are my thoughts. If you are seeing a strong drain on the system when you engage the starter, but nothing else is happening, it is not likely the clutch safety switch. That would interrupt the signal from the ignition switch to the starter so there would be no drain. .... My guess is that the heat is causing an intenal short inside the starter. That would explain both the large current drain and the lack of starter movement. ... The only way I know to confirm this is to bypass all the external wiring and manually supply power to the starter with a jumper cable. This can be dangerous so use extreme caution (e.g., out of gear, wheels chocked, don't touch the wrong thing with the hot jumper cable). Plus it will only confirm the starter as the problem if it failed to work immediately before the test. If you let the car sit for a while before you jump it, you won't know if it cooled enough to "fix" itself.

If this were my car I'd first check to see if there was any way to shield the starter from exhaust heat (e.g, wrapping on starter, wrapping on exhaust, metal shield between the two). If it was already shielded or there was nothing that could be done, I'd get a new starter as was mentioned above.

Good luck sorting this out.
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Old 06-11-2017, 04:25 AM
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Quote:
Originally Posted by Tommy View Post
This can be hard to diagnose if it only happens occasionally, but here are my thoughts. If you are seeing a strong drain on the system when you engage the starter, but nothing else is happening, it is not likely the clutch safety switch. That would interrupt the signal from the ignition switch to the starter so there would be no drain. .... My guess is that the heat is causing an intenal short inside the starter. That would explain both the large current drain and the lack of starter movement. ... The only way I know to confirm this is to bypass all the external wiring and manually supply power to the starter with a jumper cable. This can be dangerous so use extreme caution (e.g., out of gear, wheels chocked, don't touch the wrong thing with the hot jumper cable). Plus it will only confirm the starter as the problem if it failed to work immediately before the test. If you let the car sit for a while before you jump it, you won't know if it cooled enough to "fix" itself.

If this were my car I'd first check to see if there was any way to shield the starter from exhaust heat (e.g, wrapping on starter, wrapping on exhaust, metal shield between the two). If it was already shielded or there was nothing that could be done, I'd get a new starter as was mentioned above.

Good luck sorting this out.
Hi Tommy - appreciate your insights.

Regarding exhaust heat this is a Daytona Coupe and the headers rise up and out the side; i.e. they are not hear the starter. I was going to start with a starter heat shield but that would only cover up the root cause and make me feel good for the moment.

Good point on the clutch safety switch.

All things point to the starter.

Take care,

Jeff
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Old 06-11-2017, 06:25 AM
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I had a similar problem on my Kirkham awhile ago which got to where if
I stopped anywhere, then tried to start it after about 2 minutes, nothing would
happen. It was a heat soak situation with the MSD 6a1 which was mounted on
the passenger side fire wall in the cockpit. I sent it to El Paso for checkup and
aout $36 and 2 weeks later got it back - end of problem. (They replaced some
electrical components that had gone bad on it)

If you have the MSD 6a1 or similar, and find no problems with the starter, you
might want to check it out.
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Old 06-11-2017, 06:27 AM
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Jeff,

I had that happen on my car a few years ago and after trying several things I got a new gear reduction starter and it has been in there for about 6 years now and no problem at all. I never had the old one checked out but a starter shop here told me it most likely had a winding that was shortening out after it got warm.

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Old 06-17-2017, 02:49 AM
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Thanks everyone for the very helpful feedback. After checking anything wiring related I took the starter in to the rebuild shop and they said there was evidence of damage in the starter that would impact turning when hot. They should me some wire/connecter and it looked shot.

Thanks again.

Jeff
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