I didn't have the opportunity to blow out the fuel lines, but I did get it started and disconnected the diesel return line from the secondary diesel filter and noticed no fuel was coming out at low RPM but running under higher load caused fuel to come out the return line. It would rev but still didn't feel strong. The primary filter has no visible evidence of air in it. Is it possible for the lift pump or injection pump to just be weak and fail intermittently then work well enough to allow the engine to rev?

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85 300D, PlantDrive VO kit, Stage 2 performance intake
Tampa, FL