Figure 3. Four Principle Plunger Positions of Injection Cycle

Figure 1. Robert Bosch Model MW Fuel Injection Pump

TM-5-3820-256-24-5 Drilling System Well Rotary Truck Mounted Air Transportable 600 Feet Capacity Model LP-12 NSN 3820-01-246-4276 Manual
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SERVICE MANUAL GENERAL Section 1 * Code for Robert Bosch governor number RQV 350 1200 MW 43-5: R = Flyweight governor Q = Fulcrum lever model V = Variable speed governing (all-speed) 350 = Low idle pump speed 1200 = Full load rated speed MW = Fits on "MW" size pump 43-5 = Application number ** Code for Robert Bosch combination number PES 6MW 100/320 RS 1108: PE = Inline injection pump S = Flange mounted 6 = Number of cylinders MW = "MW" size pump 100 = Plunger diameter in 1/10 mm / = Pump model 320 = Number code for location of feed pump and governor R = Rotation of pump as seen from drive end (right hand clockwise) S1108 = Application number Figure 2. Injection Pump Identification Each plunger has a delivery valve above the plunger. The delivery valve, which is held on its seat by spring pressure, prevents fuel from draining out of the high pressure line between pumping cycles. The injection cycle can be described by observing the plunger in its four principle positions in the barrel. The four positions are shown in Figure 3. At bottom dead center the plunger is held down on the lowest point of the cam lobe by the plunger spring. Top of plunger is below the charging port of barrel. Fuel at supply pump pressure flows through the charging port to fill the area above the plunger. Figure 3. Four Principle Plunger Positions of Injection Cycle 1. Bottom Dead Center 3. Injection 2. Port Closure 4. End of Injection Port closure begins when the rising plunger covers the charging port and fuel is trapped above the plunger. Start of injection occurs as the plunger continues with charging ports covered, fuel is forced upward under high pressure, unseats the delivery valve and is injected into the cylinder. End of injection occurs when the plunger moves up to the point where the charging port is again uncovered by the lower helix. Fuel pressure above the plunger is relieved to the charging gallery. This pressure drop allows delivery valve and injection nozzle to seat thus ending injection. CGES-375 Printed in United States of America Page 2

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