The rollercoaster cam is the part inside the engine that operates the mechanism in the vacuum pump. If you peek in the hole that the vac pump attaches to, you'll see it on the sprocket that drives the injection pump.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

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

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]

The discs must be positioned properly as explained and the rod must be fully extended forward when the cover is tightened.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer

Tomorrow I will have to take off the pump to get inside:

https://www.youtube.com/watch?v=obCFLey6obo

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1991 300E 124.030 103.983KE 722358 03 412178
207K

1979 240D 123.123 250K (Project car)

2000 Ford Ranger, 187K

2015 Dodge Ram 1500 EcoDiesel 37K