944 Tech

Distributor Rotor: 924S, 944

A 944 that had recently come out of a maintenance service quit cold on the owner and would not restart. This was especially embarrassing since the car's owner was the daughter of an experienced Porsche technician and owner of a repair facility.

When a cursory check of the car revealed no spark, it was towed back to the repair facility for more detailed inspection and testing of the DME sensors which are located near the flywheel and which provide both timing and rpm information to the engine management computer.

Prior to replacement of these items, however, the distributor cap was removed and a much simpler and less costly problem was discovered: the distributor rotor retaining screw had come out which had allowed the rotor to twist freely on its shaft.

A review of the factory service manual revealed the reasons for this malfunction: when the rotor was replaced as part of the service, the old set screw had been reused without applying a thread locking compound and instead of applying the special rotor cement that Porsche specifies, the rotor had been simply slipped on.

When replacing rotors on these models, it is necessary to break off the old rotor and to clean the rotor shaft thoroughly. Then, prior to

installing the new rotor, the specified adhesive (Porsche part no. PNA 043.011.00) should be applied to both the shaft and the interior of the brass fitting that is embedded in the rotor.

It is imperative that the engine be cold when this operation is performed as any heat will cause the adhesive to immediately take a set, resulting in the new rotor also having to be broken off as there will not even be time to properly position the rotor before the adhesive dries. Following the instructions that come with the adhesive will insure no further problems.

The rotor set screw may be re-used providing that a medium-strength thread locking compound is applied to the threads. Or a new screw may be purchased from Porsche (part no. 999.218.007.02) which will have the compound already applied to the threads.