1)An Injection Pump is the device that pumps fuel into the cylinders of a diesel engine 2a)the main parts are shown on the picture 2b)the way it works goes like this:It rotates at half crankshaft speed in a conventional four-stroke engine. Its timing is such that the fuel is injected only very slightly before top dead centre of that cylinder's compression stroke The purpose of the fuel injection pump is to deliver an exact metered amount of fuel, under high pressure, at the right time to the injector. The injector, unlike in a gasoline engine, injects the fuel directly into the cylinder or a prechamber connected to the cylinder. The plunger (right middle in the figure) in the VE pump both rotates along its axis and performs a reciprocating translation in and out. It is the translation that performs the high pressure pumping, while the rotation is responsible for metering and sending the fuel to the correct cylinder. The cam disk is rigidly attached to the plunger. The drive shaft rotates the cam disk. The cam disk rides on four rollers (only one shown in this picture), and has four lobes. Thus for each revolution the plunger will pump four times. Note that with this arrangement the plunger stroke is constant. The metering (regulation of how much fuel is delivered) is done not by changing the mechanical stroke, but by spilling some of the fuel through spill ports, and thus changing the effective stroke . This is done by uncovering a spill port under the control sleeve at a particular angle of rotation. The other purpose of the rotation is to deliver the fuel to the correct cylinder. This is done by having four four delivery valves (only one shown in the figure), one for every 90 degrees of rotation. During a full revolution the plunger makes four strokes, one at 0, 90, 180 and 270 degrees. During each stroke the delivery port in the middle of the plunger is connected to a particular delivery valve. The timing is adjusted in response to engine RPM. At higher RPM s, the fuel pressure from the vane transfer pump is higher. Pressure changes effects a spring loaded plunger, and the resulting movement will move the cam rollers to either advance or retard the timing. There is also a cold start device which advances the idle timing manually. A mechanical governor limits the maximum speed of the engine to 4800 rpm in the bus/vanagon application and 5350 rpm in newer passenger cars. It can be seen just above the cam disk in the middle figure. A magnet valve or solenoid (shown in the figures) opens and shuts off the fuel channel between the feed pump and the metering pump. An air inlet pressure sensor is used to determine maximum amount of fuel delivered on injection pumps for turbo engines. On newer ('89 and later) naturally aspirated engines a similar arrangement is used for altitude compensation.