I have a 90 300E and a 91 300SEL. I took out the MAS relay from the 300E and plugged it into the 300SEL. FUEL PUMP works on the SEL! I found one post that talks about MAS units containing the fuel pump relay.

Do the M103 motors have the fuel pump relay included in the MAS relay? Neither of my cars have a fuel pump relay.

Why does FAST LANE show a fuel pump relay for both the 300E and 300SEL when it appear that they do not have one? Nothing against FAST LANE, my local benz shop thought the car had a fueld pump relay too.

This post is for the benefit of the next poor fellow who is trying to figure this one out. The parts books appear to not be very clear on this subject.