Shriram Fuel Injection Industries Limited

The element comprises of the barrel and the plunger which are closely matched together with clearances of 1 2 microns which provides an adequate seal even at high pressures. The functional part of the barrel is the inlet port and that of the plunger is the helix. With the plunger at the BDC the fuel enters the barrel through the inlet port. As the plunger moves upwards, it passes the inlet port and closes it this is the pre-stroke. During the rest of the stroke called the effective stroke, the fuel pressure is increased and the pressurized fuel is forced through the high-pressure pipe. The effective stroke of the plunger is terminated as soon as the plungers helix opens the inlet port. The amount of fuel delivered is controlled by position of the helix which is varied by rotating the plunger. There are several types of elements depending on the guide diameter and peak pumping pressures. Some element plungers are provided with special machined features for light load advance and cold starting.

The delivery valve comprises of the body and a fluted plunger. In a constant volume delivery valve, the functional part of the body is the conical seat and that of plunger are the retraction piston and the conical seat. The plunger is closely matched together with the body. When the element plunger moves towards the TDC the delivery valve plunger lifyts to allow fuel into the high-pressure line; when the element plunger helix terminates the fuel delivery, the delivery valve plunger closes-off the high pressure line. The volume available in the high-pressure line is increased by the retraction volume. There are various types of delivery valves depending on the guide diameter and the retraction volume. Some delivery valves have a flat machined on the piston to achieve specific fuel delivery characteristics.