DAF CF65, CF75, CF85 Series . Manual — part 421

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200416

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Inspection and adjustment

CE ENGINE FUEL SYSTEM

ΧΦ65/75/85 series

4

2

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.

CE ENGINE FUEL SYSTEM

4-8

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200416

Inspection and adjustment

2

ΧΦ65/75/85 series

4

4.4 INSPECTION, INTERNAL FUEL LEAKS

When inspecting for internal fuel
leaks, 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. All open connections must
therefore be sealed.

The common rail system is under
high pressure when the engine is
running. This pressure can rise to
approx. 1400 bar. Even when the
engine is not running, there may be
a high residual pressure in the fuel
rail (approx. 50 bar). Depressurise
the system before working on the
common rail system by wrapping the
coupling in a cloth and then
unscrewing it and collecting the
escaping fuel in a container.

Inspection, internal fuel leaks
1.

Check that all injector pipes have been
tightened to the correct torque and that there
are no external signs of fuel leakage; see
"Technical data".

2.

Disconnect the fuel return pipe (1) from the
fuel return overflow valve (2) on the rear of
the cylinder head.

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2

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200416

4-9

Inspection and adjustment

CE ENGINE FUEL SYSTEM

ΧΦ65/75/85 series

4

2

3.

Seal the disconnected fuel pipe (1) using the
special tool (DAF no. 1453151) to prevent
the return fuel escaping.

4.

Fit the special tool (DAF no. 1329476) onto
the fuel return overflow valve (2).

5.

Place the free end of the special tool
(DAF no. 1329476) in a container and start
the engine.

6.

While the engine is idling, measure the
quantity of return fuel using a stop watch and
a measuring beaker; see "Technical data" for
the maximum quantity of return fuel.

Note:
If the quantity of return fuel is within the
specified value there are no internal leaks.
If the quantity of return fuel exceeds the
specified value, the internal fuel leak must be
located.

1

2

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CE ENGINE FUEL SYSTEM

4-10

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200416

Inspection and adjustment

2

ΧΦ65/75/85 series

4

Locating internal fuel leak
1.

Take the injector pipe out of cylinder 1.

2.

Seal the connection of cylinder 1 on the fuel
rail using the special tool
(DAF no. 1453133). Tighten the plug to 30
Nm.

3.

While the engine is idling, use a stop watch
to measure the time required to fill a
measuring beaker with 360 ml of return fuel.
See "Technical data" for the minimum time
permitted for filling the measuring beaker.

Note:
Use a measuring beaker with a mark at
360ml.

4.

Remove the special tool (DAF no. 1453133)
and reconnect the injector pipe.

5.

Repeat the above steps for the other
cylinders and note the values.

Note:
When the leaking cylinder has been plugged,
the quantity of return fuel will decrease and,
as a result, the time it takes to fill the
measuring beaker to 360ml will increase.
If several high values are measured, this
indicates that there may be several leaks. If
this is the case, first check the cylinders that
give the highest values and then repeat the
test.
In the example shown in the table below
there is an internal leak in the 5

rd

cylinder,

which could be caused by a leak in the fuel
supply pipe and/or a defective injector.

Example:

6.

In the event of a leak, remove the fuel supply
pipe and the injector of the cylinder in
question; see "Removal and installation".

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Leak test results

Blocked cylinder

1

2

3

4

5

6

Time (s) to fill to 360ml

35

36

35

37

150

38