SERVICE MANUALROBERT BOSCH MODEL MW INJECTION PUMPSection 11a portion of the full stroke. Therefore the fuel quantitydelivered per stroke is smaller and the fuel pressureremains constant. If the return fuel line were blocked atthe fuel check valve assembly or orificed fuel returnhose, the pump pressure would rise to a maximum valueand the supply pump would deliver only the amount offuel necessary to maintain the maximum value. Thisself-limiting feature protects the injection pump fromexcessively high fuel pressures.Hand Priming Pump OperationEach injection pump assembly is equipped with a handpriming pump which is screwed into the supply pumphousing just above the suction valve (Figure 9). With theaid of the hand priming pump, fuel can be pumpedfrom the fuel tank through the primary and final fuelfilters into the injection pump. Approximately sixmilliliters are delivered per stroke.To operate the pump, loosen the knurled knob until theplunger can be pulled upwards. Moving the plungerupward causes the fuel suction valve to open and fuel toflow into the suction chamber. When the plunger ispressed downward, the suction valve closes thepressure valve opens. Fuel then flows through thepressure valve and towards the final filter and injectionpump housing. Operate the pump until solid fuel flowsfrom the final filter bleeder fitting. Always tighten theknurled knob after operating the pump because engineoperation with the knob loose will damage the handpriming pump.Figure 9. - Hand Priming Pump OperationCGES-185-3PRINTED IN UNITED STATES OF AMERICAPage 8
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