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

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3-5

Description of components

CE ENGINE FUEL SYSTEM

ΧΦ65/75/85 series

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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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Description of components

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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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4-1

Inspection and adjustment

CE ENGINE FUEL SYSTEM

ΧΦ65/75/85 series

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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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Inspection and adjustment

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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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