DAF CF65, CF75, CF85 Series . Manual — part 442

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2-5

General

PE ENGINE FUEL SYSTEM

CF65/75/85 series

4

5

The valve (6), back plate (8) and the pump

plunger (13) are located in the top of the pump

unit.

These parts are lubricated by the fuel.

A roller (17), tappet (15) and a spring (14) with

spring retainer (16) are situated on the bottom of

the pump unit.

These parts are lubricated by the engine

lubrication system.

The lower sealing ring on the pump unit

separates the fuel system from the engine

lubrication system.

A pressure valve (5) is fitted on the top of the

pump unit.

The function of the pressure valve is to prevent

the supply section from being interrupted by

pressure peaks from the injector pipe.

The injection timing and the quantity of fuel to be

injected are controlled by a solenoid valve (9) that

consists of an electromagnet and valve (6) with

back plate (8), via the electronic unit control.

If the solenoid valve (9) is not energised, the

valve (6) is forced against the valve stop (4) by

the force of the valve spring.

This creates a very small opening between the

space above the pump plunger (13) and the

supply ducts (2).

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15

17

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4

6

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8

10

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12

13

14

16

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PE ENGINE FUEL SYSTEM

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General

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CF65/75/85 series

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If the solenoid valve (9) is energised by the

electronic unit, the back plate (8) with the valve

(6) will be attracted by the electromagnet due to

the influence of the magnetic field.

The valve (6) closes the connection between the

space above the pump plunger (13) and the

supply ducts (2), causing pressure to build up in

the space above the plunger (13).

This causes the injection.

The fuel will now flow via the fuel supply ducts (2)

to the space above the pump plunger (13).

The valve (6) is not re-opened against the force

of the magnet by the high-pressure in the high-

pressure area, as the forces in the valve (6) slot

are balanced.

In other words, the left and right surfaces in the

valve (6) slot are equal.

The time at which the valve (6) shuts depends on

the injection timing calculated by the electronic

unit.

The time that the valve (6) remains closed, and

therefore the quantity of fuel injected, is also

calculated by the electronic unit.

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15

17

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4

6

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8

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11

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PE ENGINE FUEL SYSTEM

CF65/75/85 series

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2.3 DESCRIPTION OF COMPONENTS

Fuel lift pump with integrated primer pump

The fuel lift pump with integrated primer pump is

fitted to the rear of the pump housing. The fuel lift

pump section (1) is driven via the pulse plate (3)

by the camshaft (4) in the pump housing.

The fuel lift pump (1) is a vane pump.

The vane pump consists of a stator (7) in which

the rotor (8) with the vanes (9) can be found. The

vanes (9) are forced against the surface of the

stator (7) by the centrifugal force and two

successive vanes form an enclosed space, the

pump chamber. Due to the elliptically-shaped

stator (7), with each revolution each pump

chamber undergoes a volume increase, the

suction stroke (angle A), a volume reduction and

the compression stroke (angle B).

To achieve a good seal, the rear of the vanes are

connected to the compression pipe of the pump.

This forces the vanes against the stator with

increased pressure, resulting in a good seal.

A pressure-relief valve (5) is fitted in the fuel lift

pump to protect the fuel system against

excessive fuel lift pump pressure caused by

excessive flow resistance.

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6

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CF65/75/85 series

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Note:

Excessive fuel lift pump pressure may damage

the fuel filter element and/or leakage may occur

along seals.

A primer pump (2) is fitted for bleeding the fuel

system. To operate the primer pump (2), it must

first be loosened.

On the upward stroke, the volume above the

priming pump piston is reduced. This causes the

non-return valve (6) to close and the fuel flows

along the piston seal to the bottom of the piston.

On the downward stroke, the volume below the

priming pump piston is reduced. This forces the

fuel via the fuel lift pump section to the fuel fine

filter.

At the bottom of the fuel lift pump is a pressure-

relief area (10).

The pressure-relief area prevents fuel

penetrating the lubrication system through

sealing ring C and lubricating oil penetrating the

fuel system through sealing ring D in the event of

leakage.

A visual inspection for leaks is also possible

with this.

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D

C