DAF LF45, LF55 Series. Manual - part 291

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Inspection and adjustment

BE ENGINE FUEL SYSTEM

ΛΦ45/55 series

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4. INSPECTION AND ADJUSTMENT

4.1 BLEEDING THE FUEL SYSTEM

Stop pumping as soon as a greater 

resistance is felt. If you continue 

pumping, the fuel system may 

become internally damaged.

Note:

When the hand pump is used, the fuel system will 

be automatically bled. Air will be fed back to the 

tank through the return pipe.

1.

Unscrew the button of the primer pump and 

pull it out.

2.

Use the primer pump until a clearly higher 

resistance is perceptible.

3.

Press the button and tighten it.

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©

 200416

Inspection and adjustment

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ΛΦ45/55 series

4

4.2 CHECKING FUEL LIFT PUMP PRESSURES

When inspecting the fuel pressure, 

fuel will escape. Collect the fuel and 

avoid the risk of fire. 

Dirt in the fuel system can lead to 

significant damage to parts of the 

system. Prevent this by cleaning the 

parts before disassembly and then 

sealing all open connections.

Checking underpressure on suction side of 
fuel lift pump
1.

Disconnect the fuel pipe from the electronic 

unit cooling plate to the fuel lift pump on the 

suction side of the fuel lift pump; see 

"Removal and installation".

2.

Fit the adapter (1), special tool 

(DAF no. 1329476), between the pipe which 

has been removed and the fuel lift pump and 

couple a pressure gauge (2) to this adapter.

3.

Bleed the fuel system.

4.

Measure the underpressure when the engine 

is idling. Compare the readings with the 

specified values. See "Technical data".

5.

Remove the pressure gauge and the adapter 

and fit the fuel pipe.

6.

Bleed the fuel system, start the engine and 

check the fuel system visually for leaks if no 

further measurements are to be carried out.

Checking fuel pressure in fuel lift pump in 
front of fuel fine filter
1.

Disconnect the fuel pipe from the lift pump to 

the fuel fine filter on the delivery side of the 

lift pump; see "Removal and installation".

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©

 200416

4-3

Inspection and adjustment

BE ENGINE FUEL SYSTEM

ΛΦ45/55 series

4

2

2.

Fit the adapter (1), special tool 

(DAF no. 1329476), between the pipe which 

has been removed and the fuel lift pump and 

couple a pressure gauge (2) to this adapter.

3.

Bleed the fuel system.

4.

Start the engine and measure the pressure 

when the engine is idling. Compare the 

readings with the specified values. See 

"Technical data".

5.

Remove the pressure gauge and the adapter 

and fit the fuel pipe.

6.

Bleed the fuel system, start the engine and 

check the fuel system visually for leaks if no 

further measurements are to be carried out.

Checking fuel pressure in fuel lift pump after 
fuel fine filter
1.

Disconnect the fuel pipe from the fuel fine 

filter to the high-pressure pump on the side of 

the high-pressure pump; see "Removal and 

installation".

2.

Fit the adapter (1), special tool 

(DAF no. 1329476), between the pipe which 

has been removed and the high-pressure 

pump and couple a pressure gauge (2) to 

this adapter.

3.

Bleed the fuel system.

4.

Disconnect the electrical connectors of the 

injectors from the valve sleeve.

5.

Start the engine and measure the pressure 

when the engine is idling. Compare the 

readings with the specified values. See 

"Technical data".

6.

Connect the electrical connectors of the 

injectors to the valve sleeve.

7.

Remove the pressure gauge and the adapter 

and reconnect the fuel pipe.

8.

Bleed the fuel system, start the engine and 

check the fuel system visually for leaks if no 

further measurements are to be carried out.

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BE ENGINE FUEL SYSTEM

4-4

©

 200416

Inspection and adjustment

2

ΛΦ45/55 series

4

Check pressure drop across fuel fine filter
1.

Check the fuel pressure in front of the fuel 

fine filter.

2.

Check the fuel pressure after the fuel fine 

filter at maximum engine speed.

3.

Compare the measured pressure drop 

across the fuel fine filter with the specified 

value. See "Technical data". If the pressure 

drop is too great, the fuel fine filter must be 

replaced.