Fuel Pump Follow

The fuel pump is a submersible pump with a permanent magnet electric motor. Fuel enters the pump inlet tube after passing through a sock style filter and is pushed through the pump by the motor to the outlet. The purpose of the fuel pump is to convey the fuel reaching from its fuel tank into the individual cylinders under the requisite high pressure in order to ensure good atomization and good combustion of fuel.

Fuel pump consists of a motor, a vane roller pump, a fuel damper, and a relief valve to prevent system damage from over pressure. The pump contains a single check valve on the output side which restricts fuel movement in either direction, maintaining fuel system pressure, typically, at 40 to 45 psi when the pump is not operating.

The pump plunger is moved upwards by the two piece cam through the roller and the guide plunger. A spring forces the guide plunger with the roller down on to the cam, while a second spring presses the pump plunger on to the guide plunger, returning the latter. The suction valve is controlled by spring loaded pins. Pins, which is of adjustable length, obtains motion from the guide plunger through the lever with unequal arms, which rests on the eccentric of the regulating shaft.

When the roller lies on the base circle of the cam, the pump plunger is in its bottom position and the suction valve is closed. As the roller run up on the cam the guide plunger, pump plunger and the control pins move upwards. As the suction valve is closed, the fuel is forced through the automatic discharge, non return valve and discharge pipe into the fuel valve, from where it is injected into the cylinder. As the plunger stroke increases, the control pins also move downwards, finally lifting the suction valve from its seat. Discharge ceases at this moment and injection into the cylinder is terminated. The plunger now conveys the fuel back into the suction space. On the downward motion of the plunger the space which becomes free gets filled with fuel through the suction valve, this fuel flowing into the pump under pressure. The distance travelled by the pump plunger from the moment discharge commences until the end of discharge with the lifting of the suction valve is called the effective delivery stroke.

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