Attention: injection pump with distributor is particularly sensitive to contamination (water, mud) in fuel. The hole in the clutch of the centrifugal governor is clogged, which entails serious interruptions in the operation of the engine. This will be costly when the pump cannot be repaired without a special wire stand. Therefore, you should pay special attention to the timely replacement of the fuel filter and the removal of water from it.
The work of the injection pump
Impeller pump (low pressure pump)
The first section in the injection pump with distributors is the impeller fuel pump. It draws fuel from the tube that goes to the injection pump from the fuel filter.
Operation: The pump wheel, inserted into the movable sliders, sits in the round hole of the pump. In this hole, the wheel is slightly offset from the middle. The sliders, on the contrary, always adhere to the walls of this hole, since the pump wheel rotates when the engine is running and, they (crawlers) squeezed out by centrifugal force. They are thus sealed with the walls of the hole. When the pump wheel rotates, a volume is always formed between these sliders, which decreases towards the pressure side on the pump, i.e. to the exit. The liquid contained in this volume is thus forcibly squeezed out.
Distributor piston and lift plate
The pressurized fuel now enters the housing of the high pressure pump itself. There is - on the same shaft as the impeller of the fuel pump - the distributor piston, thanks to which the injection pump got its name. This «heart» system and it is similar in its principle of operation to the ignition distributor of a gasoline engine.
«Secret» The distributor piston consists in the fact that it is riddled with a large number of holes and recesses. Thus, it can perform both filling and injection functions.
Operation: During filling, the control gap (4) the piston is opposite the filling hole (3). The fuel pumped by the low pressure pump flows into the free space under the piston. distribution piston (1) spins longer (driven by a toothed belt from the crankshaft). The filling opening closes again, filling ends.
2 - engine stop device
5 - return line to the fuel tank
7 - nozzle
After filling is completed, the distributor piston rotates further. The filling port is now closed by the piston. Further, behind, in the high-pressure fuel pump, the protrusion of the lifting disk now runs over the roller of the roller wheel. The distributor piston, which is now rigidly connected to the lifting disc, therefore moves forward. The pressure in the high-pressure space rises above the normal pressure level in the injection pump. At this point, the distributor channel (3) due to simultaneous rotation becomes in such a way that it coincides with the outlet channel (4). By high pressure pipe (6) the fuel now under high pressure reaches the injector (7), which performs the injection. Known residual amount of fuel in the return tube (return line) (5) back into the tank again. Stop device (1) must, of course, be open, otherwise the fuel will not enter the high-pressure space at all. Fuel comes out of the filling port. The distributor piston rotates to the outlet port of the next cylinder. The protrusion on the lifting disc again runs into the roller ring. The distributor piston is pushed forward and injects fuel under pressure.
Stop device
Shortly before the diesel fuel enters the distributor piston fill port, it passes the solenoid valve - the stop device. When the key «ignition» turns to the first position, the valve is energized and the fuel path is cleared. When the engine is turned off, the power supply is cut off by the key «ignition». The stop device closes the fuel supply channel and the engine stalls. Another possibility is to close or shut off the intake air supply or exhaust - not good for stopping a diesel engine. Vehicles with automatic transmission are partially equipped with a mechanical stop device on the front of the pump, which can be used to stop the engine if the electrical stop device fails.
Centrifugal regulator
In order to cover various engine operating modes and thus be able to provide the desired injection mode as needed, a centrifugal regulator is installed on the high-pressure fuel pump. The weights of the centrifugal governor are pressed out more or less in accordance with the engine speed. It pushes the control valve through a lever mechanism, which, by opening a hole in the distributor piston, allows excess fuel to flow out. If the engine speed in relation to the position of the gas pedal is too high, the regulator opens the hole and the speed drops.
To start, the control hole is completely closed. The engine receives the full amount of fuel, but only until then. until the idle speed is reached. Then it is adjusted again.
The same happens at idle and at partial load. The centrifugal regulator compares the position of the speed and the position of the gas pedal via sensitive mechanics. When the speed set by the accelerator pedal is reached, it can be adjusted again.
The maximum engine speed is also limited by the centrifugal governor. If the engine exceeds 5200+100 rpm, then the control hole is released. The engine cannot run faster.
Injection regulator
At increasing speeds, the fuel must be injected earlier, while ignition still takes place at the set time. This advance control is taken over by the injection controller. It is also installed in the injection pump.
If the engine speed increases, the low pressure pump in the injection pump rotates faster. The fuel pressure therefore increases. This fact is used in injection control. The fuel pressure acts on the piston and moves it against the spring force. The roller ring is rigidly connected to this piston. With increasing fuel pressure - and also with an increased speed - the piston of the roller pin shifts it relative to its axis. The lugs of the lifting disc therefore run up against the rollers earlier; i.e. injection occurs earlier. When the speed drops, the piston and with it the roller ring moves back.
Load dependent injection timing
For achievement «soft» In addition to the already mentioned speed control, the injection controller is also affected by a load-dependent delivery rate. Start of delivery - the point in time when fuel is injected into the cylinder (also called moment of injection). changes as the engine load changes. The load condition of the engine is recognized by the injection pump as follows:
- The gas pedal is pressed hard, the speed is low - the load is high;
- Accelerator pedal released, engine speed high (downhill) - no load.
At a high engine load, the high-pressure fuel pump performs the injection moment earlier; at low load, on the contrary, later.
Switchable load-dependent injection timing
In order to do everything to the fullest, the 55 kW engine has an electric actuator located on the injection pump, which cuts off the load-dependent injection timing at speeds above 3000 rpm. Switching on and off is carried out by a control device for automatic regulation of the warm-up time (see section «Preheat system»).
This has the following effect: the composition of the exhaust gases is improved and fuel consumption is slightly reduced.
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