I have a 1991 300SE that has been sitting for over a month. Now it will not start. The fuel pump is not being energized when the ignition switch is turned to the start position to crank the engine. The fuel pump does make some noise and the measured votage varies but for the most part it is not running while cranking. The fuel pump does run if I connect 12V directly to the pump terminals. I did verify that there is spark while the engine is cranking.

I have ordered a new overload protection relay and a new(used) MAS control unit. Hope they solve the problem.

After looking at the control circuits for the 1991 300SE, I really love the simplicity of my diesels.