Try runing the Engine without the Fuel Fill Caps on; to eliminate the Tank Vent as a cause.

I was looking in the manual and there is a Fuel Heater and somewhere there what appears to be a Thermostat for the Fuel Heater. I do not know if it could block off the flow or not if it was not working right.

I think I would bypass everthing to the rear by runing a Fuel hose with a pre-filter from the Fuel Supply/Lift Pump to a container of clean Diesel Fuel and see if the Engine will run OK on that. If so you need to trouble shoot the Fuel lines from their back.

There could also be something sticking inside of the Fuel Supply/Lift Pump.

Also one of the other members recently said that if your crakcase pressure cannot vent itself it puts pressure on the Shutoff Valve and will shut you down if it the pressure is high enough.

A different Engine but I put my Thumb over the crankcase breather hose and in about 7 seconds my Engine started to bog down. I tried this several times but did not let it shutoff all the way.

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84 300D, 82 Volvo 244Gl Diesel