DIY Video: Porsche 911 Bosch Starter Motor and Solenoid Rebuild
Here is a detailed video series explaining how to rebuild and test your factory original Bosch starter motor and solenoid.
Note: The following information is for educational use only. Before proceeding please read my disclaimer page.
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The venerable Bosch starter motor I rebuilt here was used on the entire run of 915 transmissions (1973-1986) and is very similar to the earlier 901 transmission starters as well. This early design was designed to be easily rebuildable so when mine started acting up, I figured I would give it a go before scrapping it.
This first video focuses on the removal, disassembly, and inspection of the starter:
This second video covers the reassembly, bench testing, and reinstallation process:
Before embarking on this process, if you just want to see how to bench test the starter out of the car, watch this short video:
If you just want to see how to bench test the solenoid out of the car, watch this short video:
Now I know what some of you may be thinking: “Why didn’t you just toss the heavy factory starter and get one of those new-fangled lightweight hi-torque units?” That is a valid question. The new units are very light and have a design based on Denso starters. If that name sounds familiar it is because Denso is an OE supplier to Toyota.
Well the reason is two-fold: First, I wanted to see if I could save an original Porsche part rather than discard it (and save a few bucks in the process). Second, the new units are indeed higher torque, due to a more modern design with a reduction gear.
If you don’t set it up correctly you could cause more problems. You have to make sure the teeth on the starter gear make full contact with the flywheel ring gear teeth. To do this the starter needs to be clocked (rotated) correctly and spaced axially (in and out) correctly. If you have partial tooth engagement, the starter is going to eat up the ring gear prematurely, and then you are looking at an engine drop (using this procedure) plus separating the gearbox and engine (using this procedure) to replace the ring gear.
Here is an Amazon link to a compatible high-torque unit. The choice is yours, but the purist in me says try rebuilding your OE starter first. 🙂
After completing this procedure, my starter fires up every single time I turn the key, with no drama whatsoever.