DAF CF65, CF75, CF85 Series . Manual — part 441

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General

PE ENGINE FUEL SYSTEM

CF65/75/85 series

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5

2. GENERAL

2.1 LOCATION OF COMPONENTS

1.

Pump units

2.

Pump housing

3.

Fuel fine filter

4.

Fuel lift pump

5.

UPEC electronic unit

6.

Primer pump

7.

Pressure relief valve

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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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2.2 SYSTEM DESCRIPTION, UPEC FUEL SYSTEM

The fuel lift pump (3) feeds the fuel from the fuel

tank (1) through the cooling plate (2).

The purpose of the cooling plate (2) is to ensure

that the electronic unit does not become too hot.

The fuel lift pump (3) is fitted opposite the pump

housing (5) and is driven by the camshaft in the

pump housing.

From the fuel lift pump, fuel is forced towards the

fuel fine filter (4).

For the purpose of constant bleeding, there is a

calibrated bore in the fuel fine filter.

After the filter, the fuel enters the pump

housing (5).

The pump units driven by the electronic unit are

fitted in the pump housing (5).

The pump units force the fuel at high pressure

(approx. 1600 bar) to the injectors.

At the end of the supply channel, there is a

pressure relief valve (6) that connects the supply

and discharge channels at a specific supply

channel pressure. The pressure relief valve

ensures a good degree of filling for the pump

units. The discharge channel is connected to the

fuel tank (1) return pipe via the fuel fine filter.

8,5 bar

5 bar

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General

PE ENGINE FUEL SYSTEM

CF65/75/85 series

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5

The injector leak-off pipe is connected to the

return pipe to the fuel tank (1) via a non-return

valve in the fuel fine filter.

If the system has been 'open', the fuel system can

be bled by means of the integrated primer pump

in the fuel lift pump (3).

Pump unit
Operating principle

Situation A
In this situation the pump plunger (2) makes the

suction stroke.

Due to the constant overpressure in the supply

area of the fuel system, the high-pressure area

above the pump plunger (2) is filled via the fuel

supply ducts (3).

Situation B
In this situation the pump plunger (2) makes the

compression stroke.

As the valve (5) has not yet closed the link to the

fuel supply ducts (3), there is no pressure

build-up.

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B

PE ENGINE FUEL SYSTEM

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General

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CF65/75/85 series

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Situation C
In this situation, the injection timing is

determined.

The solenoid valve (4) is activated by the

electronic unit.

In this way, the valve (5) closes the link between

the space above the pump plunger (2) and the

fuel supply ducts (3).

There is now a pressure build-up above the pump

plunger (2), causing fuel to be injected via the

injector (6).

Situation D
In this situation the quantity of fuel to be injected

is determined.

The solenoid valve (4) is no longer activated by

the electronic unit

The valve (5) opens the connection between the

space above the pump plunger (2) and the fuel

supply ducts (3).

The fuel pressure above the pump plunger (2) will

be quickly reduced.

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