If you've ever admired a Porsche 928, you understand what a solid, capable Grand Touring automobile this is. The car was certainly a technical marvel in it's time, and can now be found at very reasonable prices in the secondary market. But there are some technical issues that can make proper repairs a bit difficult.
The first thing a prospective Porsche 928 owner might want to do is check out the supportive and knowledgeable community over at Rennlist. This group has solved many repair and part sourcing problems that would put the average auto enthusiast to shame. One particularly ingenious solution is the The Engine Guardian Water Pump Drive System (EGDS) ™ developed by Perfex Manufacturing. Water pump failure in the Porsche 928 can be a very big deal with camshaft and valve train damage resulting from a broken timing belt. Many thanks to Ed at Perfex and the 928 community as a whole for addressing the quirks of this fabulous car.
One very common problem is the electrical wiring harness, particularly the engine section. The connectors seem to hold up well, but the wire and sheathing become very brittle and crack, open or short out, many times out of sight, causing poor running and outright no start conditions. Again thanks to Ed at Perfex, I decided to look into possible solutions.
The best answer for owners who want to keep their cars running correctly seems to be a complete harness replacement. Of course, the harness for earlier cars is NLA (Porsche term for "you're out of luck") and would probably break the bank if you could find one. I see this as a four part project- remove the old harness, source the needed wiring and connectors, copy the harness and reinstall it in the car.