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CONSTRUCTION AND WORKING OF CAV FUEL INJECTION PUMP

The function of the fuel injection pump is to measure and deliver the correct quantity of fuel at high pressure to the injector. CAV fuel injection pump is most commonly used in  diesel engines. 


Construction :

It is a plunger type pump. It has a reciprocating plunger which reciprocated inside the barrel. The plunger has a helical groove. This groove extends as vertical groove to the top. The plunger is operated by a cam mechanism.

Working : 

The plunger is moved up by a cam and return back to is initial position by tension spring. The plunger can also be rotated by the rack and pinion arrangement. Fuel Delivery valve is seated in its seat by the force of the spring. Two ports are provided in the barrel. One is known as supply port and other is known as spill port. This port is opened and closed by the moving plunger. The fuel passage is connected to fuel injector. 

When the supply port is opened., The fuel is filled in the barrel. When the cam rotates, it will lift the plunger up. The moving plunger first closes the supply and spill ports. Then the fuel above the plunger is compressed and high pressure is developed. Due to this high pressure, the delivery valve is lifted off and the fuel flows through the fuel passage to the atomizer.

The quantity of fuel delivered is controlled by the rack and pinion arrangement. When the rack moves, the pinion is rotated. The plunger is rotated inside the barrel. It alters the effective stroke of the plunger. Thus, amount of fuel supplied is varied. 

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