DAF LF45, LF55 Series. Manual — part 292

©

200416

4-5

Inspection and adjustment

BE ENGINE FUEL SYSTEM

ΛΦ45/55 series

4

2

4.3 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.

}

}

}

i400679

1

2

BE ENGINE FUEL SYSTEM

4-6

©

200416

Inspection and adjustment

2

ΛΦ45/55 series

4

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

i400680

i400682

©

200416

4-7

Inspection and adjustment

BE ENGINE FUEL SYSTEM

ΛΦ45/55 series

4

2

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 3

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".

i400681

Leak test results

Blocked cylinder

1

2

3

4

Time (s) to fill to 360ml

35

36

200

37

BE ENGINE FUEL SYSTEM

4-8

©

200416

Inspection and adjustment

2

ΛΦ45/55 series

4

7.

Check the fuel supply pipe for damage and

signs of leakage.

Leakage in the fuel supply pipe can be

recognised by erosion tracks (lines) on the

nose of the supply pipe. If necessary or if in

doubt, replace the fuel supply pipe.

8.

Check that the injector fuel connection is not

leaking.

Leakage in the injector fuel connection can

be recognised by erosion tracks (lines) in the

socket of the fuel connection . If necessary or

if in doubt, replace the injector.

Note:

If fuel has been found in the lubricating oil,

extra attention must be paid to the O-rings of

the injectors, as these have most probably

been damaged by increased pressure in the

return circuit as a result of an internal leak.

Note:

The following guidelines must be adhered to:

-

If the injector is defective, both the injector

and the fuel supply pipe must be replaced.

-

If the fuel supply pipe is defective and in

addition the sealing surface with the injector

is damaged, both the injector and the fuel

supply pipe must be replaced.

-

If the fuel supply pipe is defective and the

sealing surface with the injector is not

damaged, the fuel supply pipe must be

replaced but the injector can be reused.

9.

Fit the injector and fuel supply pipe. See

"Removal and installation".

10. Again inspect for internal fuel leaks to check

that there is no leakage.

i400776