Model and year?
For your info, I swapped out the Fuel Pump Relay coz I had an intermittent stalling problem when braking to a stop from high speeds.
Yes, it is the big black one with round pins, and is the one closer to the battery.It has the word "kickdown" printed on the label.They are known to go bad coz the original ones are not well sealed - moisture gets in...
And by the way, my battery is also on the passenger's side.
After the swap, the problem still existed for about 1 to 2 weeks.Then it disappeared for good. This was about 3 months ago and I have never had a stalling incident since. My car used to have a stall at least once a week, sometimes up to 2 times in one day.
I was skeptical about solving my stalling problem by swapping the Fuel Pump Relay coz it didn't go away instantly.Now, I believe that was the fix.
The part cost me about 85 Singapore Dollars (approx. USD50).Merc parts are cheap here...
Good luck and let us know if you need more info.
Babybenz 1991 190e 1.8