Out of the blue - it won't start!

[Thumper]

No fancy tools for me. I used the largest channellock wrench I could find at Home Depot. It fit over the top and without squeezing the retaining ring, I was able to catch the tabs on the side of the retaining ring with the sides of the channellock jaws and twist counterclockwise. Once it's broken loose, it spins off rather easily. Porsche does put a dab of silicone sealer on the ring and sending unit to "lock" the ring into place. It helps to remove the dab of sealer before attempting to break the ring loose.

If the channellock's hadn't worked, my next attempt would've been a strap wrench. It's pretty tight quarters, but the retaining ring isn't really torqued down very tight. Worst case, I could've broken off the ring and just bought a new one, as it's plastic (I'm amazed at the amount of plastic Porsche uses).