Originally Posted by latemodel21

here is the part of the schematic that shows the entire IC pump circuit. It is designated as "M44".

The relay that you seek is part of the "N65" Pulse Module. it is located in the same box as the fuse (drivers side on real cars ... passenger side on yours : )

However, I have NEVER ever heard of this (relay) being the failure. with rare exception, the pump fails (fuse blows) by 20,000 to 30,000 miles AND replacing the pump and fuse solves the problem.

Worth noting on my 1st SLK32 (which I bought at 30,000 miles) the pump was not running when I bought it. the fuse was blown and I replaced it (fuse only) ... and it worked (until 50,000 ?) when the fuse blew agian ... once more I replaced it (fuse only) and it lasted for more than 10,000 or 20,000 additional miles until it blew one more time (and this time the pump actually had failed) So. I finally replaced the pump for the FIRST time near 80,000 miles. NOW, on my 3rd SLK32, I bought it with 17,000 miles AND ITS FUSE WAS BLOWN ALSO when I bought it. I replaced the fuse and have put 1,000 miles on it since and it is still working fine. MY POINT... while this part does NOT last the life of the car, I Suspect it is slightly under-fused and often prematurely replaced. (I seem to recall a mention somewhere that a higher value fuse is used in other models, but never looked into it.

Hope the schematic helps,
Chris