(4) Operation of the Supply Pump a. As shown in the illustration below (in case of HP3 pump), the rotation of the eccentric cam causes the ring cam to push Plunger A upwards. Due to the spring force, Plunger B is pulled in the opposite direction to Plunger A. As a result, Plunger B draws in fuel, while Plunger A pumps it to the rail. In the case of the 4-cylinder engine used with the HP3 pump, each plunger pumps fuel in a reciprocal movement during the 360° cam rotation. Conversely, in the case of the 6-cylinder engine used with the HP4 pump, 3 plungers pump fuel in a reciprocal movement for each one rotation of the cam.
Delivery Valve Suction Valve Plunger A Eccentric Cam Ring Cam SCV Plunger B Plunger A: Complete Compression Plunger B: Begin Compression Plunger A: Begin Intake Plunger B: Complete Intake Plunger B: Begin Intake Plunger A: Begin Compression Plunger A: Complete Intake Plunger B: Complete Compression QD0707E NOTE: There are 3 plungers for the HP4. 12