Porsche Repair: 1980 Porsche 911SC, fuel injection computer, porsche 911sc

Question
Hi Dave - 1980 Porsche 911SC. Car is running perfectly, except non-starting when engine is hot. Once engine is hot and car is turned off for 1/2 hr., the engine will not start. It acts like a "vapor lock" from many years ago, but car is fuel injected. I have had all of the obvious items replaced - fuel pump, spark plugs, complete tune up all to no avail. Any ideas on this mysterious problem?  

Answer
Hi Doug,

The obvious question is what "thing" is being affected by the heat the most.  It could be the fuel...if it is boiling because a hard line is touching the exhaust manifold, for instance, the newly created oxygen bubbles in the lines would negatively affect how the fuel injection computer gets things going the next time.

More likely, the wiring at the starter and to the starter could be getting hot enough to raise the resistance level of the wires...this reduces the voltage you'd expect at the starter when you're trying for a warm start.

Even more likely is the heat is affecting the starter solenoid and it doesn't pump out enough torque to start until it cools down sufficiently.

First thing I'd do is to consider how your wiring and then your starter might be affected by proximity to very hot things.  Then, unless you want to buy a new starter, is to buy a starter blanket.  Essentially, it's purpose is to reduce the heat the starter absorbs.  It might be an interesting experiment.

Good luck.

Dave