5.5 Injection Pump

The diesel fuel injection pump performs three functions. It pressurizes the fuel, precisely times the delivery of fuel to the injectors, and meters the amount of fuel delivered. The pump is driven by the camshaft drive belt at 1/2 crankshaft speed. Internal parts are lubricated by the diesel fuel, so no routine maintenance is required. If clean fuel is used, and the fuel filter and water separator properly maintained, the pump can be expected to operate reliably for a long time.

Most diesel fuel system problems are caused by a problem outside the injection pump. If injection pump problems do occur, it will most likely be due to wear and high mileage. Internal injection pump wear is most often characterized by an unsteady idle, or the inability to precisely adjust pump timing. Internal repairs to the injection pump require specialized knowledge and equipment, and parts for rebuilding are not generally available. Faulty pumps must be serviced by the pump manufacturer or other qualified diesel fuel injection repair shop.

Parts are available to service the stop solenoid, the external throttle and advance mechanisms, the barometric element, and the outlet check valves. Adjusting injection pump timing requires some special tools. More serious problems generally require replacement of the injection pump.