DAF 95XF. Manual - part 390

4

XF ENGINE FUEL SYSTEM

Inspection and adjustment

95

XF series

3-8

3.4

INSPECTION OF INJECTOR OPERATION

Fuel or test fluid discharged by an
injector may penetrate the skin and
be very harmful to your health.
Make sure the fuel jet is discharged
into a suitable container.

Evaluating the spray pattern, spray angle, and
sound is practically impossible. New injectors or
injectors which have been used for some time
cannot be tested in this way.

1.

Place the injector on an injector tester.

2.

First allow the injector to inject a number of
times.

3.

Check the injector for:
-

opening pressure

-

leaks

-

nozzle holes.

Opening pressure
1.

Check the opening pressure by slowly
building up the pressure inside the injector.

Leaks
1.

Dry the nozzle immediately after the final
injection.

2.

Increase the pressure to the opening
pressure minus 20 bar. Within approx.
10 seconds, fuel must have ceased to leak
from the nozzle. A moist nozzle is
permitted. If the injector does not pass the
fuel leakage test, the injector body (nozzle)
must be replaced.

Nozzle holes
1.

Quickly build up pressure in the injector and
check whether all the holes are fully open.

2

©

 0008

4

95

XF series

Inspection and adjustment

XF ENGINE FUEL SYSTEM

3-9

3.5

INSPECTION OF FUEL SYSTEM FOR LEAKS

To avoid deforming the fuel tank,
the pressure in the fuel tank may
not exceed 0.4 bar.

1.

Fit a pressure reducing valve connection to
a fuel filler cap (without bleeding) and
connect it to the fuel tank.

2.

Dry the inspection points.

3.

Pressurise the fuel tank (maximum 0.2 bar).

4.

Open the union nut (A) a few turns to check
whether the non-return valve is leaking into
the banjo bolt (B). If it is leaking, this banjo
bolt should be replaced.

5.

Check the entire fuel system (low pressure
area) for leakage.

6.

Depressurise the system and replace the
banjo bolt with integrated non-return valve
in the filter head with a normal banjo bolt.

7.

Remove the valve covers.

8.

Re-pressurise the system (maximum
0.2 bar).

9.

Check the leakage seal and the side
connection of the injectors for leakage.

Note:
Engine oil may be used to detect leaks at
the O-ring.

10. Fit the valve covers.

11. Replace the normal banjo bolt with a banjo

bolt with integrated non-return valve.

i 400333

A

B

I 400332

2

©

 0008

4

XF ENGINE FUEL SYSTEM

Inspection and adjustment

95

XF series

3-10

3.6

BLEEDING OF FUEL SYSTEM

Fuel is released during bleeding of
the fuel system. This fuel must be
collected, bearing in mind the risk
of fire.

1.

Open the bleed screw (1) on the filter body.

2.

Using the hand pump (2), pump fuel
through the system until fuel without air
bubbles comes out of the bleed screw.

3.

Close the bleed screw (1).

i 400172

1

2

2

©

 0008

4

95

XF series

Inspection and adjustment

XF ENGINE FUEL SYSTEM

3-11

3.7

CHECKING OF GALLERY PRESSURE

Fuel is released when the gallery
pressure is checked. This fuel must
be collected, bearing in mind the
risk of fire.

1.

Remove the banjo bolt from the fuel pump
supply pipe and replace it by a banjo bolt
containing an extra connection.

2.

Connect an attenuated pressure gauge with
a range of up to 5 bar to the banjo bolt.

3.

The weight of the vehicle should
approximate the maximum combination
weight.

4.

Engine at operating temperature.

5.

Select the highest gear but one.

6.

Apply full throttle starting from approx.
900 rpm until the maximum loaded engine
speed has been reached.

7.

Measure the gallery pressure during
acceleration and at maximum loaded
engine speed. Compare the values as
indicated. See “Technical data”.

i 400194

2

©

 0008