DAF XF105. Manual - part 87

1

©

 200528

1-9

System description

DMCI ENGINE MANAGEMENT SYSTEM

XF105 series

Start of injection
When the injector (2) is also activated, the 

injector valve (2a) releases the path to the return 

(7). The pressure above the injector plunger (2d) 

is now slowly released via a throttle (2b). Now the 

pressure under the injector needle (2e) is able to 

lift the injector needle. Fuel is now injected.

The fuel pressure (x) now experiences a small dip 

because fuel is being injected, but the pressure 

immediately rises again. The needle is now 

lifted (y).

Start of injection

1

2

c

b

b

d

e

a

X

Y

3

P

5

6

4

7

i400797

a

1

DMCI ENGINE MANAGEMENT SYSTEM

1-10

©

 200528

System description

XF105 series

Pressure reduction
To ensure that the injector needle (2e) closes 

quickly enough, the fuel pressure in the injector is 

first reduced. The pump unit (1) is no longer 

activated and, as a result, the pump unit valve 

(1a) re-opens the supply and the pressure in the 

fuel injection pipe drops. Injection still continues.

The fuel pressure (x) now decreases. The injector 

needle is still lifted to its maximum extent (y).

Pressure reduction

1

2

c

b

b

d

e

a

X

Y

3

P

5

6

4

7

i400798

a

1

©

 200528

1-11

System description

DMCI ENGINE MANAGEMENT SYSTEM

XF105 series

End of injection
The injector valve (2a) is now no longer 

energised. In the meantime, the fuel pressure in 

the injector has decreased and the injector 

needle (2e) is closed by the spring above the 

injector plunger (2d).

The fuel pressure (x) now decreases even 

further. The injector needle is about to close (y).

End of injection

1

2

c

b

b

d

e

a

X

Y

3

P

5

6

4

7

i400799

a

1

DMCI ENGINE MANAGEMENT SYSTEM

1-12

©

 200528

System description

XF105 series

Closed
The fuel pressure has now dropped as much as 

possible and the injector needle (2e) is pushed 

down by the spring above the plunger (d).

The fuel pressure (x) is now at its minimum level. 

The injector needle has closed (y).

Closed

1

2

c

b

b

d

e

a

X

Y

3

P

5

6

4

7

i400800

a