Fuel system - Design and function

Fuel shut-off valve supplied with voltage during stopping General

Fuel shut-off valve for stopping the engine. The valve changes the direction of flow in the fuel system during the stop procedure.

A.Solenoid valve

B.Valve housing

Connections in valve housing, markings:

T.Inlet from fuel tank

F.Outlet to feed pump

P.Inlet from fuel filter

I.Outlet to injection pump

The diagram shows the fuel flow during operation.

Tightening torque for pipe connections: 22 Nm.

Function

During operation

The valve is not connected and the fuel has the normal direction of flow. The fuel pump (3) induces fuel from the tank (5) via the pre-filter (1) after which the fuel is pressed through the fine filters (4) and on to the injection pump (7).

During the stop procedure

When the key switch is moved to the stop position (“S”) the solenoid valve (2) is activated. The valve therefore changes the direction of the fuel flow to and from the feed pump, whereby an underpressure of 0.3–0.4 bar is built up in the injection pump’s fuel chamber. This prevents filling of the pump element and the engine stops (the pump element requires overpressure for filling). The overflow valve (6) prevents fuel flowing into the injection pump via the return pipe.

12/24 Volt

Fuel shut-off valve supplied with voltage during operation

General

12/24 Volt

Fuel shut-off valve for stopping the engine. The valve changes the direction of flow in the fuel system during the stop procedure.

A.Solenoid valve

B.Valve housing

Connections in valve housing, markings:

T.Inlet from fuel tank

F.Outlet to feed pump

P.Inlet from fuel filter

I.Outlet to injection pump

Tightening torque for pipe connections: 22 Nm.

When the engine is switched off the valve is in the stop position. It is not supplied with voltage. With the valve in this position the engine will not start.

Function

During operation

The valve is connected and the fuel has the normal direction of flow. The fuel pump (3) induces fuel from the tank (5) via the pre-filter (1) after which the fuel is pressed through the fine filter (4) and on to the injection pump (7).

During the stop procedure

When the key switch is moved to the 0 position or the stop button is pressed, the solenoid valve (2) releases. The valve therefore changes the direction of the fuel flow to and from the feed pump, whereby an underpressure of 0.3–0.4 bar is built up in the injection pump’s fuel chamber. This prevents filling of the pump element and the engine stops (the pump element requires overpressure for filling).

The overflow valve (6) prevents fuel flowing into the injection pump via the return pipe.

12/24 Volt 0 Volt

Flow diagram, fuel shut-off valve

Engine in operation (the solenoid valve is activated).

Flow diagram, fuel shut-off valve

The stop function is activated (the solenoid valve is not activated)