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Diesel direct injection and glow plug system
Servicing Diesel direct injection system
Checking injection adjuster control range

The control range of the injection adjuster can be checked with help of final control element test and at the same time calling-up measured value block 04. To do this it is required to activate the control element Commencement of injection valve -N108 and then exiting the final control element test with key -C-. Using this sequence the commencement of injection valve continues to be pulsed so that with help of measured value block 04 (display zone 3) the injection adjuster control range can be read.

Special tools, testers, measuring instruments and auxiliary items required

  • ◆ Fault reader V.A.G 1551 or vehicle system tester V.A.G 1552 with cable V.A.G 1551/3
  • ◆ Test box V.A.G 1598/18
  • ◆ Hand multimeter V.A.G 1526 or multimeter V.A.G 1715
  • ◆ Adapter set V.A.G 1594
  • ◆ Current flow diagram

Test sequence

  • ‒ Connect fault reader V.A.G 1551 and select engine electronics control unit (address word 01); selection is carried out with engine idling.
 
→ Indicated on display:
Rapid data transfer     HELP
Select function XX
  • ‒ Input 03 for "Final control diagnosis" function.
 
→ Indicated on display:
Rapid data transfer     Q
03 Final control diagnosis
  • ‒ Confirm entry with Q key.
 
→ Indicated on display:
Final control diagnosis     ⇒
Commencement of injection valve -N108

Note:

Control of the individual control elements is limited to 30 seconds. The following switching sequence must therefore take place rapidly so that sufficient time to read off the specifications exists.

  • ‒ Press C key.
  • ‒ Input 08 for "Read measured value block" function and confirm with Q.
 
→ Indicated on display:
Read measured value block     HELP
Input display group number XXX
  • ‒ Press keys 0, 0 and 4 for "Display group number 4" and confirm entry with Q key.
 
→ Indicated on display:
Read measured value block 4     ⇒
840 rpm     0.95 BTDC     0.95 BTDC     3 %
  • The displays in display zones 3 and 4 must fluctuate within following control range:
  • ‒ Specification display zone 3
         Lower range1°after TDC...4.0°before TDC
         Upper range 14.0...17.4°before TDC
  • ‒ Specification display zone 4
         Lower range 2...5%
         Upper range 90...95%

Because the fault reader display is slow the displayed figures vary greatly. Therefore ensure that only in
display zone 3 the lowest figure lies between 1.0 and 4.0 and the highest figure lies between 14.0 and 17.4
and in display zone 4 the lowest figure lies between 2 and 5, and the highest figure lies between 90 and 95.

  • ‒ If specifications are not attained, check commencement of injection valve as follows:
 
V23-0296

Electrically checking commencement of injection valve (N108)

  • ‒ Switch off ignition.
  • ‒ Disconnect connector on injection pump =>Fitting locations overview, Page 23-4 .
  • ‒ → Carry out resistance measurement between contacts 2 + 3 using hand multimeter V.A.G 1526.
         Specification: 12 ... 20 ω

If the specification is not attained:

  • ‒ Replace commencement of injection valve (N108)

Checking wiring connection to commencement of injection valve (N108)

  • ‒ Switch off ignition.
  • ‒ Disconnect connector on injection pump =>Fitting locations overview, Page 23-4 .
  • ‒ Connect test box .

The following wiring connections are to be checked for open circuits and/or short to positive or negative.

 
V28-1074
  • ‒ → Wiring from connector contact 2 to test box socket 51.
  • ‒ Wiring from connector contact 3 to test box socket 68.
  • ‒ Rectify any open/short circuit as necessary.
  • ‒ If neither an open or short circuit exists, renew Diesel direct injection system control unit.

Power unit > Diesel direct injection and glow plug system > Fuel preparation system Diesel injection > Servicing Diesel direct injection system > Checking injection adjuster control range

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