3208 – Fuel Injection Pumps

A. Fuel Injection Pump uses a reverse flow check valve (RFC).

B. Fuel Injection Pump uses an orificed delivery valve (ODV).

C. Fuel Injection Pump also has an orificed delivery valve (ODV).

D. Fuel Injection Pump uses an orificed reverse flow check (ORFC).

Operation Of Fuel Injection Pumps

The main components of a fuel injection pump in the sleeve metering fuel system are barrel (A), plunger (B), and sleeve (D). Plunger (B) moves up and down inside the barrel (A) and sleeve (D). Barrel (A) is stationary while sleeve (D) is moved up and down on plunger (B) to make a change in the amount of fuel for injection.

Fuel Injection Sequence
(1,2,3) Injection stroke (positions) of a fuel injection pump. (4) Injection pump camshaft. (A) Barrel. (B) Plunger. (C) Fuel inlet. (D) Sleeve. (E) Fuel outlet. (F) Lifter.

When the engine is running, fuel under pressure from the fuel transfer pump goes in the center of plunger (B) through fuel inlet (C) during the down stroke of plunger (B). Fuel can not go through fuel outlet (E) at this time because it is stopped by sleeve (D), (see position 1).

Fuel injection starts (see position 2) when plunger (B) is lifted up in barrel (A) enough to close fuel inlet (C). There is an increase in fuel pressure above plunger (B), when the plunger is lifted by camshaft (4). The fuel above plunger (B) is injected into the engine cylinder.

Injection will stop (see position 3) when fuel outlet (E) is lifted above the top edge of sleeve (D) by camshaft (4). This movement lets the fuel that is above, and in, plunger (B) go through fuel outlet (E) and return to the fuel injection pump housing.

When the sleeve (D) is raised on plunger (B), fuel outlet (E) is covered for a longer time, causing more fuel to be injected in the engine cylinders. If sleeve (D) is low on plunger (B), fuel outlet (E) is covered for a shorter time, causing less fuel to be injected.

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