No start when hot. Starter? Solenoid?

[pfbz]

1982 911 SC.

I am having a very occasional no-start when hot. Recently, a 95 degree day + 3 hour trip + gas stop = no start. At first, I thought I heard nothing, no click, but it could have been that the fuel pump plus traffic noise was just masking it. Later, I definitely heard a faint click.

Seems like this problem is usually attributed to two factors:

• Heat soak on the starter itself causes the malfunction.
• Deteriorated wiring + ignition switch + heat causes too low voltage at the starter solenoid.

Is it really a combination of these two items? If the starter solenoid is sticking due to heat soak, but works 99% of the time, might the extra voltage with the hot-start bypass push the solenoid past the sticking point?

I'm willing to replace the starter with a Pelican sourced high-torque starter, but it obviously would be simpler and much less expensive to put in the hot-start relay plus maybe new tranny and battery ground cables if it would do the trick. Since the problem occurs so rarely already, 'install it and try it' probably isn't going to tell me much. Has anybody installed the hot-start kit and continued to have heat-soak no-start problems?

[GH85Carrera]

On my factory original starter if it got a heat soak it would lock up. When the repair shop took it apart they said it was "very dry" on the bearings. After it was lubed up it worked fine for a while. Then it went back to lockup when hot. I finally just replaced it. The repair shop could not get the rear bearing out because he did not have the proper puller.

[jpnovak]

Plunger on the bendix gear is sticking. The solenoid is not strong enough to pull against it when it heat soaks and expands making the problem worse. Because the solenoid can not pull against it the solenoid does not close and make the motor turn.

If you take them apart you will find the grease all dried up. you also need to lightly sand the oxide off the plunger and the housing so that they slide very free. Lube the bearings and bushings while you have it it apart. I have done this on several starters with excellent results.

Fastest way to fix is replace the starter.

[blucille]

hi torque starter from our host will fix all your troubles.

[pfbz]

What everyone has said makes perfect sense. But the inner engineer in me is wondering is still wondering if the hot-start relay isn't also a solution....

• Old starter = dried lube = more physical resistance.
• Hot starter = parts expansion = more physical resistance.
• Old wiring + undersized wiring + heat = lower solenoid voltage = less magnetic power in the solenoid.

Is seems only when all three of these conditions exist does the no-start problem rear it's ugly head... I'll jack it up and check the solenoid trigger terminal voltage vs. the starter main power terminal voltage.

If there is a significant drop, I might try just putting more power to the solenoid, via the relay and hopefully to overcome the dry lube/heat expansion problems. If there isn't a significant voltage drop, new Starter.

[pfbz]

Read another discussion of the same situation, and a test that makes sense.

If you have a hot-no-start condition, and if JUMP starting from another running vehicle starts the car, then a hot start relay will also likely fix the problem.

Turning the key alone uses battery voltage, about 12.6V if the battery is completely charged...
When jump starting, you are using the alternator output voltage of the other vehicle, around 14V.

So if a 1.5V increase in voltage will engage a hot/sticky solenoid, eliminating a similar voltage drop to the solenoid should also work.

Suppose I'm overthinking this a bit??

[Joe Bob]

The 914s were particularly vulnerable to the hot start problem. Mid engine, exhaust passing under the trans mounted starter on the way to the rear.....trust me, the problem is well documented and discussed to death.

[Joe Bob]

Deeply profound.....

[Nick Triesch]

Mine got hot on a Summer trip a year ago and would not start in the mountains. I push started it and got it home put it on jackstands and cleaned all the starter wires with contact cleaner. (took them off, put them on) They were very filthy. Then I got my rawhide mallet and gave it a few good whacks. Started right up and has been working for a year now.