W126 91 300SE fuel filter replacement
 

The first step in the CD manual procedure (07-725) is "reduce gauge pressure, open closing cap for this purpose." Does this mean remove the fuel filler cap? Is there another closing cap?

Thanks,
Sixto
91 300SE
81 300SD

Sixto:

I've changed the fuel filter on same yr/make/model twice, once with the gas cap left on; once with it off. I didn't seem to make alot of difference as far as how much fuel flowed downward once things were loosened up. It's not the cleanest maint. task, but not too bad.

I did remove the battery ground strap first and back the car up on ramps for ease of access. Be sure to change the copper O-rings. If you encounter leakage after you put it back together, snug down the connections some more. Things need to be fairly snug.

o-rings? How many and where? Do you have the part numbers?

Thanks,
Sixto
91 300SE
81 300SD

Sixto:

2 O-rings - part number 007603-012102 - dealer part number.
These are used in one of the fuel lines that connects to the fuel filter. I'll include the notes I took when I first performed this task. While it may not be of too much help, be aware of task 0780.4 - Replacing fuel filter in the Maintenance Manual which is on the 126 CD-Rom.

Tools used:
8" long 1/4" extension
10mm socket - 1/4"
1/4" dr. ratchet
17mm open-end wrench
3/4" and 7/8" open end wrench
Flat blade screwdriver
Phillips screwdriver
Ramps to back car up on
Pan to catch residual fuel - some will leak

- Back car up on ramps
- Remove ground strap from battery
- Fuel filter/pump closest to right rear wheel. Remove plastic
shroud that encases the fuel pump/filter assembly. 2 bolts.
10mm socket & 8" extension.
- Loosen/remove 2 screws that fasten mounting bracket around
the fuel filter. It's best to first loosen the fuel line connections
on both ends of the fuel filter. This takes a 17mm open end and
a 3/4" open end on one side and a 7/8" on the other. The SAE
wrenches are used on the counter nuts that are on each end
of the fuel filter. You may find that the size of the counter nuts
varies between the different brands..ie...dealer, Mann: Bosch.
- Remove filter after you get connections from both ends off. Be
prepared for some drippage as things are loosened up. The 2
brass washers(see part # at top) are used on the side of the
fuel filter closest to the right rear wheel. The dealer sold me 6,
but I used only these two. The other side had no washers.
- Snug the connections down really good. If you encounter
leakage afterwards, try to snug down a little more.

Correction - In my first reply I mentioned "copper" washers/O-rings. In my last reply I referred to them as "brass" . Copper is correct; brass is not. Sorry for any confusion.

yes
 

Check for leaks afterward, you may need the extra copper washers for one of the lines. I did a month ago after that
filter replacement.
The instructions given are good.
cheers.

An old post that I responded to 15 yrs. ago. Would like to add a comment. Maybe it will help someone else down the road.

The OP asked what gasket part number to use for an M103 fuel Filter. My response was 007603-012102.

If by chance you order a fuel pump from wherever and it does not come with gaskets, you will need the same 2 gaskets - 007603-012102.

Also - the comments on the 2nd thread above that list SAE sizes 3/4" & 7/8" were for the counter nut(s) used on the fuel filter I used at that time. These sizes will vary, depending on the fuel filter purchased. Since then I have seen many different counter nut sizes; some metric; some SAE.

The 007603-012102 gasket is harder to find these days 3rd party. I have found that in this case the easiest(maybe not cheapest) place to source them is at an MB dealer.

Good update ! Especially taking notice about scarcity of gasket sources.:)