Clean and degreas the area and see where the leak is.

If you have an MW Fuel Injection Pump do not loosen the 13 or 14mm Nuts (2 Nuts per each Element) that hold the Fuel Elements into the Fuel Injecion Pump Housing; that is how the set the Fuel amount when the Fuel Injection Pump is on the Test Stand.

Check for leaks around the Delivery Valve Holder (the part you remove to take out the Delivery Valve Springs when you Drip Time). Some times they develop a crack down by the threads or I have also seen the Crush Washer eaten through by the high pressure Fuel (on other Bosch fuel Injection Pumps).
If it is an M Pump they have an O-ring as well as a Crush Washer.

Also there are Crush Wahers on the Banjo Bolts of the Fuel Inlet and the IP Overflow/Pressure Valve and I suppose the Plastic tubing itself could crack.

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84 300D, 82 Volvo 244Gl Diesel