1986 Intermintent Does Not Start
 

1986 3.2 911 Carerra has died a couple times in the last month. Symptoms exactly the same as when the DME Fuel Filter Relay conked out about 10 years ago. Just dies like shut off at key. Won't start sounds like no fuel.

I did a full debug of the relay and found it was not getting voltage to the Fuse nor the fuel pump hot wire. Took the fuel pump out. It spins fine on floor with 12v. Ordered a Fuel Pump Relay. While waiting for new part, put the fuel pump back in. Car started right up with old relay.

Drove for a week (close to home) and it died at parking lot of grocery store. Installed new relay in the parking lot. Still would not start. Towed it home. Did same tests on relay. All looks good. Pulled the fuel pump again. Spun it on the garage floor. Reinstalled and the car started right up.

New pumps are 200. Is there a way to test them for sure or is it a guess item? I have not done any pressure or current draw tests yet. Ideas, suggestions?

If the engine doesn't run after key is turned on, the fuel pump will not be reactivated. The DME (computer) will only power the fuel pump for a short duration unless engine fires up and runs. I suspect you diagnosed proper operation.

When you get into another no-run situation, it will help a lot to know if you have a lack of fuel or ignition.

Had a similar problem years ago with my 930. Drove me crazy. Ended up being a faulty cdi box.

Swap out the yellow relay in engine bay ... Had this problem a few years ago.

Does your car have a factory alarm system on it? The alarm module is capable of causing this symtom, as well as flywheel sensors.

Mine had the same symptoms, drove me nuts. Check for spark. No fuel and no spark can be caused by a bad fly wheel sensor. Ask me how I know...

The flywheel sensors and the cylinder head temp sensors are easy to check with a multimeter. Mine turned out to be a bad speed sensor. Wish I'd checked it before I bought the new fuel pump...

You realize the fuel pump relay is the DME relay correct?

The fuel pump only runs when the key is in the start position or the DME senses the car is running.

You can jumper 12 volts to the fuel pump fuse and walk around to the back and hear fuel "shoosing" (tech term) through the regulator. If you want to get real technical you could put a gauge on the test port on the left distributor rail.