X03

so yeah basically where is it at? I bought another one to hopefully get rid of this CEL I have on now. Its supposed to be behind the battery near the ECU right? When i look though i dont see anything, am i supposed to remove the ECU to get to the relay? any help is appreciated.

YNVDIZW124

it's next to the OVP relay...The one next to the KLIMA relay...

lkchris

It's the one that looks just like the one you bought.

Remove the sheet of plastic behind the battery to see it.

oliverb

If you have a 1990 as listed in your sidebar info., IIRC, there is no separate fuel pump relay. The "ECM" (sometimes called the "ECU") is the larger black box behind the battery. It has a knob on top that must be twisted to remove the module and controls 4 functions. In Stu Ritter's "E-Class Owner's Bible", he lists: fuel injection, fuel pump relay, and AC compressor control. The module also controls the air injection pump. This module is very expensive! Mine was first replaced 5 years ago because of an intermittent problem with the fuel pump relay portion. Found a used one for $50. That one was replaced a year later with a new one at dealer cost (independent repair shop) of $300 - list was $500! The AC portion of the used one failed that time. Not a bad item to have on hand if yours is original since it controls so many important functions and can't be purchased at the corner auto parts store. Stu Ritter lists it as being used in the 124 Es from 1986-1992. Don't know if it controls all 4 things for earlier years, but I do know in 1990 it contains the fuel pump relay. Also, did you retrieve a code that said "fuel pump relay"? I ask because when mine failed for both the fuel pump and AC, the CEL did not come on.