Page 58 - E BOOK ENGINE MECHANICAL M2

3. FUEL SYSTEM

(2) Supply Pump
The supply pump transfers the fuel from the fuel tank into the supply pump using a feed pump that it
is driven by the rotation of the supply pump camshaft. The camshaft lobe in the supply pump actuate
the reciprocal movement of two spring loaded plungers. The plungers have an intake and an exhaust
strokes which receives and delivers fuel through the suction and deliver valves respectively. Fuel is
delivered to the common rail when the cam lobe pushes the plunger to exhaust the fuel to the deliv-
ery valves. The electronically controlled suction control valve, which is located between the feed
pump and the suction valve, regulates the amount of fuel that is supplied to the feed pump in accord-
ance with the pulses received from the Engine-ECU.

<Construction Diagram>
Fuel pressure limiter valve

Fig. 3-5

◆ Feed pump: It transfers the fuel from the fuel tank, and delivers it to the plungers through the
suction valve.
◆ Regulator valve: It returns the fuel to the fuel tank when the outlet fuel pressure from the feed
pump becomes higher than a predetermined value.
◆ Suction control valve: It regulates the amount of fuel that is delivered to the common rail.
◆ Plunger: A spring loaded piston driven by the spring tension and the camshaft lobe. When the
spring pushes the plunger, fuel enters through the suction valve into a cylinder area known as
the high-pressure chamber. When the lobe pushes the plunger, the plunger forces the fuel
through the delivery valve to the common rail.
◆ Suction valve: It works as one-way valve, and prevents the fuel which delivered to the common
rail from flowing back to the feed pump.
◆ Delivery valve: It works as one-way valve, and stops the fuel back flow from the delivery side
when the fuel is suctioned into the high-pressure chamber.

<Feed Pump>
It is a trochoid gear type pump driven by the supply pump camshaft. It is located on the back part,
inside the supply pump. The feed pump draws fuel from the fuel tank and feeds it to the supply pump.

Fig. 3-6

Pub. No. PTAE1228 3 - 4