949187 Volvo.Penta O-ring

The fuel system consists of the injection pump assembly (injection pump proper, governor, feed pump), automatic timer, fuel filter, injection nozzle, injection pipe, and other parts.Fuel is fed from the fuel tank through suction pipe to the feed pump of the injection pump assembly, and then to the fuel filter, injection pump, and injection nozzle. The excess fuel is returned from the injection pump to fuel tank. (1) A Type Injection Pump Proper The Bosch A type injection pump is used which is constructed as illustrated.The injection pump, that forces fuel into the injection nozzle under pressure, is provided with a mechanism to increase or decrease the amount of fuel. It has one plunger and delivery valve for each cylinder.The plunger, pushed up by the camshaft and pushed back by the plunger spring, moves up and down in the plunger barrel on a predetermined stroke to feed fuel under pressure. In so doing, it opens and closes the suction and discharge ports to adjust the fuel injection rate.The camshaft is supported by two taper roller bearings at its ends, provided with cams operating the plunger and one operating feed pump.The camshaft is driven by the injection pump gear at half the engine speed.(a) Plunger The plunger has a groove obliquely cut in its side as shown. There is a hole at its top which leads to this groove. The plunger barrel has a suction/discharge port.The fuel delivered to the injection pump is forced as described above by the rotating motion of the camshaft or reciprocating motion of the plunger.With the plunger at the lowest position (BDC), fuel flows through the suction/discharge port into the plunger barrel.As the camshaft rotates, the plunger moves up, and when the plunger top surface and suction/discharge port line up, fuel begins to be compressed.When the plunger moves up further, the fuel pressure is increased until the delivery valve is pushed up against the delivery valve spring. While the delivery valve is pushed up, the fuel flows through the injection pipe to be pressure-fed to the nozzle.As the plunger moves further up and the groove cut in plunger meets the suction/discharge port, the high-pressure fuel flows through the hole in the plunger and runs through the groove back to the suction/discharge port, completing pressure feed of fuel. The plunger stroke during which fuel is fed under pressure is called the effective stroke. The fuel injection rate is increased or decreased according to the engine load by turning the plunger at a certain angle to change the position where the groove meet the port during its upward stroke, thus increasing or decreasing the effective stroke. The illustration above shows the mechanism that varies the plunger's effective stroke.The control rack is coupled to the floating lever in the governor. As the control rack moves to the right or left by the operation of the accelerator pedal or governor, the control sleeve in mesh with the rack turns. Since the bottom of the control sleeve is in mesh with the claw of the plunger, the plunger turns with the control sleeve, thus varying the effective stroke to increase or decrease the fuel injection rate.The more the control rack is pulled toward the governor, the less the effective stroke and fuel injection rate.Each plunger is in mesh with this single control rack and turns by exactly the same amount.(b) Delivery Valve The fuel compressed to a high pressure by the plunger pushes the delivery valve up, spouting out. As soon as the pressure feed of fuel completes, the delivery valve is brought back to its original position by the delivery valve spring force to block the fuel passage, thereby preventing back flow of fuel.The delivery valve goes further down until its seat surface is held tight. During this stroke, the fuel is drawn back from the injection pipe side, instantaneously dropping the residual pressure between the delivery valve and nozzle. This draw-back effect improves the end break of an injection from the nozzle and prevents after-injection dripping.A delivery valve stopper is provided on the top of the delivery valve spring. The stopper limits the lift of delivery valve and prevents valve surging during high speed rotation. It also reduces the dead volume between the delivery valve and nozzle, thereby stabilizing the fuel injection rate.(c) Overflow Valve The overflow valve, mounted to the top of the pump, stabilizes the fuel temperature in the injection pump and temperature distribution to make sure that the amount of fuel injected into each cylinder is maintained constant.The valve is a ball seal type. When the fuel pressure in the pump housing exceeds a predetermined level, the valve opens to allow fuel back into the fuel tank. (2) RSV Type Governor The RSV type governor is a centrifugal type all-speed governor coupled to the camshaft of the injection pump. The governor not only controls the maximum and minimum speeds but also automatically controls the engine speed at any intermediate speed position. The governor, as shown, consists of flyweights mounted to the injection pump camshaft. When the flyweights turning on the flyweight supporting shaft open outward, the roller mounted to the end of flyweight arm pushes the end of the sleeve in the axial direction. The governor sleeve, being made integral with the shifter through a bearing, moves only in the axial direction.The shifter, mounted to the guide lever hung on the supporting lever shaft to the governor cover, prevents rotation. The floating lever is mounted to the middle of the guide lever by the shaft with the bottom end as the fulcrum, whereas the top of the lever is coupled through the shackle to the control rack.The start spring, attached to the top end of the floating lever, always pulls the control rack in the direction that fuel is increased. The turning shaft of the swivel lever is fitted into the bushing of the governor cover and its center is eccentric with respect to the mounting position of the governor spring installed to