Porsche 911SC l980 hard tostart, runs for about 15 minutes and

#1

wouldn’t start again until the engine cools and will start again and run for onlyl5 minutes. Is it fuel pump? Does this car have a crank sensor?

#2

To see if it is a fuel problem you could try spraying some starter fluid into the intake and see if it tries to run on that. If not, check for spark at the plugs.

#3

People involved with Porsche automobiles usually have a close relationship with a mechanic,where is yours?

You need to find a mechanic and let him move in with you.You will save on transportation costs.

#4

It’s going to be near impossible to guess at the problem until it’s known if the problem is fuel or spark related.
You need to determine if there is fuel pressure and/or spark when the car will not start.
Your complaint could point to an ignition fault (coil, ign. module, etc.), fuel injection fault, or electrical (ign. switch, relay, etc.)

When it will not start you could try giving the intake a healthy shot of aerosol carb cleaner and see if it starts. If it does, you know the problem is fuel related.

If it’s fuel related then your best bet is to find a Porsche mechanic because this car uses CIS fuel injection. This system requires some special tools and fuel pressure gauge along some expertise to diagnose.

I’m familiar with CIS but am a bit hesistant to even start explaining how this quirky system works.
While I don’t think the fuel distributor is the problem you might say a silent prayer that it’s not. Fuel distributors, even reman ones, are kind of up into the four digits price-wise.

#5

Part of your post is a bit unclear to me but if the car has a hot-start problem after being shut off it’s possible the injectors could be leaking off. This is a common problem with CIS injectors.

When they’re leaking off on a warm engine this causes the engine to flood. After cooling it will restart as much of the dribbled gasoline has evaporated and the flooding condition has pretty much disappeared.