I think it was one of our members who posted this within the last 2 weeks:
Acetone Diesel Mix used to free Plungers in Fuel Injection Pump
I decided to try another experiment which was to see if I could cycle acetone through the fuel system by mixing it with diesel and driving it which would have the benefit of heat and vibration and flushing. Some trial and error suggested that I could run the car on about 1:14 acetone: diesel before the engine started running poorly. After 1 gallon of acetone and 14 gallons of diesel in multiple small batches the car starts and run perfectly on normal fuel.

I have never read of someone using Acetone as the Person above did. I think Marvel Mystery Oil would also work.

A Fuel Injection Pump sitting on the Shelf after being calibrated (meaning the Fuel was clean) can suffer from a sticking Plunger. A Fuel Injection Pump with Diesel Fuel from the Tank can get stuck Plungers due to dried Fuel and Rust.

In the past I have loosened up stuck Plungers by removing the Delivery Valve Holder and Delivery Valve assembly and taking a piece of about 1/8" or slightly thicker Brass Brazing Rod and using as a punch to tap gently on the top of the Plunger. The trick is to do that the Fuel Injection Pump Camshaft is best at the lowest position so that the Plunger has someplace to go.
The MW Pumps do not have a removable Side Cover like the M Pumps do that would allow you to visulize the position of the Tappets.

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84 300D, 82 Volvo 244Gl Diesel