Engine Cut-out 2X

[wsp8]

Looking for a solution to this: while out driving last night, the engine in my '76 911S twice cut-out at speed and stopped. At the time it immediately restarted and ran fine. Although now it will not start.

Fuses good and fuel flows fine so searching for an illusive electrical issue, I suppose. Any ideas?

[jester911]

If it isn't fuel then it is electrical. Plugs,points,wires, coil, ground.

Time to get out the multimeter.

[AZ1977911]

Check your points gap... If the gap gets bad enough they can stick. A quick fix to get home is to slide a business card between the point contacts a few times to clean them.

Good luck.

[wsp8]

New plugs, wires, coil and dist. cap. No points as it has a Petronix under the cap. Thanks for the idea, though. It's the cutting out and then being able to restart right away that baffles me.

[Paulporsche]

Do you have a Permatune CD? If so, quite few members have said they have had problems like this once the unit heats up.

Check the fuse, relay and connections for the fuel pump.

Check the round black connectors located under the dash/steering wheel.

[wsp8]

I DO have a PermaTune unit. Thanks for the additional list of items to check. Got it towed to my garage last night (before the heavy rains) so I can run diagnostics this weekend.

[ljowdy]

I know this is an old thread however, I do a lot of repairs, modifications and tune up for people that own replica Porsche 550's and Speedsters. On one occasion I had a customer that complained of intermittent spark. The car ran fine then would stumble then resume. Often times, he would stop the engine and several minutes later, the car would again run fine only to begine the stumbling again.

I diagnosed the problem and discovered that this Petronix unit was not grounding properly to the base of his distributor. I removed the Petronix module and lightly sanded the base of the module and the distrubutor base. Once everything was reinstalled, I added a drop of Loctite to the module mounting screw and the engine ran great and for the last year, he has had no similar problems.

[wsp8]

Thanks for the thought. I just re-installed the ignitor so we'll see if that helps. However, I've also just made a new harness from the coil back to the CDI and ignition switch lead. The wire from CDI to coil (+) had a break in the skin, was quite frayed and, I think, grounding to neg. as that wire unshielded right next to it. We'll see tomorrow.

[wsp8]

For anyone who was following, it WAS the wire from the CDI to terminal 15 on the coil, apparently, as my new harness has cured the problem (after ten starts and twenty-five miles or so)! Now to repair the original for that period look.

Thanks for everyone's help.

[Mysterytrain]

My 78SC did that right before it self destructed. Mine would cut out at speed. I could flip the ignition switch to 'off' and then restart while I was coasting and she was fine. I replaced fuel pump, fuel pump relay, ignition switch...etc and couldn't find the problem. Nor could the local gang of Porsche mechanics. One day disaster struck and the engine died for good. Turns out the distributor seized, sheared off the distributor drive gear which dropped down into the case. The gear then got a ride on the intermediate gear and was pushed out of the side of the case. That was the bad news. I had the engine rebuilt and bumped up to a 3.2 SS with the same CD box, same ignition switch, same coil etc the only part of the ignition that is different [rebuilt] is the distributor. Well, guess what my problem is gone. Before you waste a lot of time dicking around with the other things pull the cap and see how much play you have in the distributor shaft. Look inside the cap and see if it is eating the copper conductors. On mine the bearings were toast. A $300 distributor rebuild may save you thousands!