Well I broke everything open today and Installed one of the M pump washers (by necessity, long story). I drove about 80 miles and had no issues. It kind of seems wrong though... what could happen by doing this? The p/n of the washer i used was 1410105021.

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1981 240D 4sp manual. Ivory White.

If it isn't leaking, nailing, or running rough, probably no harm no foul.

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Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Okay, it's running rough... no leaks however. How does this work? Is there some lost displacement due to the smaller o-ring? What gives?

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1981 240D 4sp manual. Ivory White.

Usually leaks or "nailing" after servicing DV's is due to failing to torque the holder correctly and not seating the crush washer. If you got any dirt in there, it can cause an injector to "hang up" a bit. If the DV were moved any, the mating surfaces no longer align either. It can take a couple hundred miles of running before everything settles back in.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

I torqued to 45nm, surfaces were pretty spotless. I read something about a spring having to settle in to the slightly different height? In any event I managed to find some of the correct size washer. It’s not really nailing or anything, just running rougher than it was. Using throttle doesn’t take away as many shakes as it used to.

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1981 240D 4sp manual. Ivory White.