The low pressure fuel system

TM 9-2320-312-24-2

Systems Operation Section

(8) Fuel supply line

(11) Fuel filter

(35) Fuel transfer pump

(9) Fuel pressure regulator

(12) Fuel tank

Fuel pressure regulator (9) consists of an orifice

The low pressure fuel system serves three functions.

and a spring loaded check valve. The orifice is a

The low pressure fuel system supplies fuel for

flow restriction that pressurizes the supply fuel.

combustion to injectors (7). Also, the low pressure

The spring loaded check valve opens at 35 kPa

fuel system supplies excess fuel flow in order to

(5 psi) in order to allow the fuel which has flowed

cool the unit injectors and the low pressure fuel

through the orifice to return to fuel tank (12). When

system supplies excess fuel flow in order to remove

the engine is off and no fuel pressure is present,

air from the system.

the spring loaded check valve closes. The spring

loaded check valve closes in order to prevent the

The low pressure fuel system consists of four basic

fuel in the cylinder head from draining back to the

components:

fuel tank.

Fuel pressure regulator (9)

Fuel filter (11)

Fuel tank (12)

Fuel transfer pump (35)

Fuel transfer pump (35) is mounted on the back of

unit injector hydraulic pump (1). The fuel transfer

pump pushes pressurized fuel out of the outlet port

and the fuel transfer pump draws new fuel into the

inlet port.

Fuel is drawn from fuel tank (12) and flows through

two micron fuel filter (11).

Fuel flows from fuel filter (11) to the inlet side of

fuel transfer pump (35). An inlet check valve in the

inlet port of the fuel transfer pump opens in order

to allow the flow of fuel into the pump. After the

fuel flow has stopped, the inlet check valve closes

in order to prevent fuel flow out of the inlet port.

Fuel flows from the inlet port in the pump to the

outlet port, which also has a check valve. The outlet

check valve opens in order to allow pressurized fuel

flow out of the pump. The outlet check valve closes

in order to prevent pressurized fuel leakage back

through the pump.

Fuel flows from the outlet port of fuel transfer pump

(35) to the fuel supply passage in the cylinder head.

The fuel supply passage is a drilled hole which

begins at the front of the cylinder head. The fuel

supply passage extends to the back of the cylinder

head. This passage connects with each unit injector

bore in order to supply fuel to unit injectors (7). Fuel

from the transfer pump flows through the cylinder

head to all of the unit injectors. Excess fuel flows out

of the back of the cylinder head. After the excess

flows out of the back of the cylinder head, the fuel

flows into fuel pressure regulator (9).