SAI Pump diagnostics with Durametric,Bentley and Multimeter - FAILED !

[Qmulus]

I do repairs like this almost weekly. My guess is that you either forgot to hook up the power wire to the 40 Amp fuse from the alternator when you did the rebuild, or you have a break or bad connection at the connections from the engine harness to rear harness. Wires pretty much never break in the middle unless they get pinched, etc., and generally you will have multiple issues and shorts and often smoke... That doesn't match your failure descriptions. That wire has no splices, so the likelihood of having a break in the middle of the run is virtually nil (barely a physically damaged harness of course).

Personally, I would first inspection the connection from the engine harness to the rear harness. If there is no power there, then I would disconnect the battery, and get to the back of the alternator and inspect. If you have to pull the alternator to get to it, so be it. My guess is that your problem lies there.

As for the SAI pump, if it is at all noisy, it must be disassembled, the bearings should be replaced, and the commutator turned and polished. Use the best quality bearings with good seals, not just skate board bearings. They don't last long.

One of the big issues with those pumps is that the carbon from the brushes gets into the bearings, first causing noise, then they seize and finally windings burn. If the motor has stopped or doesn't run full speed or has trouble starting, check continuity and shorting of the windings (I do on all of them). Most that have seized have damaged windings IME. If you don't polish the commutator (and brushes for that matter) and remove ALL the carbon dust, the carbon will get into the bearings (especially the one on the fan side) and cause the same problem again. These pumps are not a very good design, and they don't last particularly long. There are a couple of other issues, like exhaust getting into the pump, that is common on Audis that use the same pump, but I haven't seen it on the Porsches.