DAF CF65, CF75, CF85 Series . Manual — part 419

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200416

3-5

Description of components

CE ENGINE FUEL SYSTEM

ΧΦ65/75/85 series

4

2

3.4 FUEL RAIL PRESSURE-LIMITING VALVE

The fuel rail has a pressure-limiting valve so that
the rail pressure is maintained at a safe value in
emergency situations.

The fuel rail pressure control circuit is normally
active. This consists of the fuel lift pump, fuel
pump control solenoid valve, high-pressure
pump, fuel rail, rail pressure sensor and
electronic unit. If a fault occurs, the rail pressure
can no longer be controlled. This can rise to the
actuating pressure of the fuel rail pressure-
limiting valve. This pressure is approx. 1650 bar.
In the open position all surplus fuel flows without
pressure to the fuel tank return connection.

The valve includes a sealing cone (1), a valve
body (2), a spring (3) and a return connection with
quick-release coupling (4).

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CE ENGINE FUEL SYSTEM

3-6

©

200416

Description of components

2

ΧΦ65/75/85 series

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3.5 FUEL RETURN OVERFLOW VALVE

The injectors are mounted in the cylinder head.
The injectors do not have a separate return
connection. In place of this there is a longitudinal
bore in the cylinder head that meets the injector
bores of all cylinders coinciding with the height of
the return ports of the injectors. A pressure relief
valve is mounted at the end of the bore to prevent
vapour bubbles forming in it and to prevent it
emptying after the engine is turned off. This valve
maintains a residual pressure in relation to the
return pressure of 1.2 to 2.0 bar.

The pressure relief valve consists of a spring-
loaded plunger (1) and a housing (2) with quick-
release inlet and outlet connections (A and B
respectively).

A

B

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200416

4-1

Inspection and adjustment

CE ENGINE FUEL SYSTEM

ΧΦ65/75/85 series

4

2

4. INSPECTION AND ADJUSTMENT

4.1 INSPECTING FUEL LEVEL ELEMENT

To prevent deformation of the fuel
tank, the delivery pressure in the fuel
tank must not exceed 0.4 bar.

Note:
To prevent dirt from entering, first clean the
exterior of the fuel tank.

1.

Fit a pressure reducer valve connection on a
fuel-tank cap (without bleed vent) and
connect the cap to the fuel tank.

2.

Slowly increase the pressure until the
system audibly blows off via the pressure
relief valve and check the opening pressure
of the fuel level element. See "Technical
data".

3.

De-pressurise the fuel tank and remove the
tank cap with the air connection.

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CE ENGINE FUEL SYSTEM

4-2

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200416

Inspection and adjustment

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ΧΦ65/75/85 series

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4.

Remove the fuel level element.

5.

Check the angular displacement of the fuel
level element and the resistance value. See
"Technical data".

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