No Start when Hot

No Start when Hot

> A while back, my car had acquired the bad habit of refusing to start
> after it had been running at highway speed for extended periods, but
> after cooling for 20 to 30 minutes would start up just fine.
> In trying to start the car, there is no response from the engine, no
> attempt to crank. The dash lights go on, all electrical components are
> working, but the start command to the engine is met with NO response at
> all. Took it to the dealer, he said that a wire to the starter was a bit
> loose, tightened it, checked all the other wires in that part of the
> system, but couldn't be sure that that would be the end of the problem.
> It ran fine for a while.

Symptoms could indicate a starter with worn brushes/dead spots. At high temperatures, this results in larger than normal resistance and the starter won't turn. Sometimes just tapping the starter will be enough to restore contact and you'll be able to crank the engine. When the starter cools, you usually can start the car. However, over time this problem gets worse and the episodes of no starts when hot increase in frequency. Replacing my starter cured the identical problem on my car - the starter was pretty bad inside.

Occasional no starts can also be the result of poor contact on the ignition switch. However, this problem can occur anytime, hot or cold. With the key held in the start position, wiggle it around and up and down - this usually intiates contact and the car will start.

Steve -87S4/auto/GPW

I had the same problem. Now, I have a new starter motor, battery, and cable from the battery to the starter motor....and no more problem ;-)

The basic problem is usually one of not enough current to the starter. Three basic things can cause this:

- broken strands in the cable (boosting the resistance)
- bad connections
- not enough juice in the battery to start with

Michael Cottam

I had seen this problem before, on a non porsche. It turned out to be the stator in the starter. When the starter got hot, via absorbing heat from the warmed up engine, the starter wouldn't work properly. I figured this out, by removing the starter and taking it to a place that rebuilds starters. They tested the starter and it tested fine. However when I told them about the hot start scenario, they placed the starter in an oven to warm it a bit. They used a setting of 300, for 10 minutes, I think. At that point there was almost a direct short in the stater....... I thought that was somewhat intersting.

Food for thought,

90 Cognac S4

Randy Venier has done a great job of documenting the fix he did to his car.
Randy's Fix

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