Glow plugs on the 220D were only working intermittently, like there was a short in the circuit, and I know the plugs are all good and wired correctly. Salt shaker would either cherry up on the first or second try or I might spend an hour trying to get them to glow. So I took it to a neighborhood shop that specializes in auto-electric, they have always been solid with my other vehicles (this is the first time I've taken the Benz there), but now after having the car for two weeks, dude tells me they believe there is a 'vacuum component' to the system causing problems and they are going to have to 'smoke it out'. I've been looking at schematics, and I see no vacuum lines having anything to do with the glow plugs. When I took it in, I had figured the gorilla knob was shot or there was a short somewhere else.

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1969 220D - 4spd std
1973 220D - 4spd std