DAF LF45, LF55 Series. Manual - part 311

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General

CE ENGINE FUEL SYSTEM

ΛΦ45/55 series

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5

Location of components, production date 

 2003-49 (chassis number  0L253643) 

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3 4

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CE ENGINE FUEL SYSTEM

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General

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ΛΦ45/55 series

4

1.

Suction pipe to electronic unit cooling plate

2.

Fuel rail pressure sensor

3.

Fuel pipe to fuel rail

4.

Fuel rail

5.

Fuel return overflow valve

6.

Fuel rail pressure-limiting valve

7.

Return pipe from fuel return overflow valve

8.

Fuel pipe to fuel fine filter

9.

High-pressure pump leak-off pipe

10. Fuel pipe to fuel lift pump

11. High-pressure pump

12. Return pipe to fuel tank

13. Fuel pump control solenoid valve

14. Fuel pipe to high-pressure pump

15. Fuel supply pipe

16. Fuel fine filter

17. Fuel pipe from electronic unit cooling plate

18. ECS-DC3 electronic unit

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General

CE ENGINE FUEL SYSTEM

ΛΦ45/55 series

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2.2 SYSTEM DESCRIPTION, ECS-DC3 FUEL SYSTEM

The fuel lift pump (4a) draws the fuel from the fuel 

tank (1) through the cooling plate of the electronic 

unit (3).

The purpose of the cooling plate (3) is to ensure 

that the electronic unit does not become too hot.

The fuel lift pump (4a) is fitted against the high-

pressure pump (4c) and is driven by the camshaft 

gear.

From the fuel lift pump, fuel is forced towards the 

fuel fine filter (5).

After the filter, the fuel enters the high-pressure 

pump (4c) via the fuel pump control solenoid 

valve (4b), which controls the amount of fuel 

going to the high-pressure pump. Fuel not taken 

in by the high-pressure pump returns via the by-

pass valve (4d) to the fuel lift pump supply pipe 

and part of it is used for lubricating the high-

pressure pump.

The high-pressure pump forces the fuel under 

high pressure to the fuel rail (6). The fuel rail 

distributes the fuel among the injectors (7). The 

fuel rail (6) also functions as an accumulator to 

ensure that large fluctuations in pressure, 

resulting from injector openings and pump 

pressure pulses, are prevented as much as 

possible.

The pressure in the fuel rail is registered by the 

rail pressure sensor (6a). The electronic unit uses 

this data to control the high-pressure pump (via 

the fuel pump control solenoid valve), so that the 

rail pressure can be kept at the desired level. The 

desired pressure is not constant, but depends on 

the operating conditions.

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CE ENGINE FUEL SYSTEM

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General

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ΛΦ45/55 series

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A pressure relief valve (6b) is fitted at the end of 

the fuel rail. If the pressure in the fuel rail rises too 

high (in emergencies only), this valve ensures 

that the excess fuel flows back to the return pipe. 

The return pipe is connected with the return pipe 

to the fuel tank (1).

The electronic unit uses the present rail pressure 

to calculate the time during which the injector 

needs to be opened in order to obtain the desired 

injection quantity.

A pressure relief valve (8) connects the injector 

leak-off ducts in the cylinder head with the return 

pipe to the fuel tank (1). This pressure relief valve 

prevents the fuel from flowing out of the injectors 

when the engine has stopped running.

If the system has been "open", the fuel system 

can be bled using the primer pump (2a), which is 

integrated in the water separator/coarse 

filter (2b).