Checking modulating piston movement sender and metering adjuster — VW

The metering adjuster is an electromagnetic swivelling positioner which is controlled by the control unit via a directed duty cycle (on-off ratio). The eccentric shaft on the metering adjuster moves the modulating piston on the high pressure piston and thereby regulates the quantity of fuel injected.

The modulating piston movement sender informs the control unit of the position of metering adjuster -N146 and therefore stipulates the amount injected.

Special tools, workshop equipment, 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 1598/31
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 (V.A.G 1552) and select engine electronics control unit with the "Address word" 01. When doing this the engine must be running at idling speed.
(Connecting fault reader and selecting engine electronics control unit => Page
01-4
.)

Rapid data transfer
HELP
Select function XX
Indicated on display:

Press keys 0 and 8 for the function "Read measured value block" and confirm entry with Q key.

Read measured value block
Enter display group number XXX
Indicated on display:

Press keys 0, 0 and 1 for "display group number 001" and confirm entry with Q key.

Read measured value block 1
⇒
840 rpm
6.5 mg/H
1.480 V
87.3 5C
Indicated on display:

Check coolant temperature in display zone 4.
Specification: at least 85 °C

Continue with check only when coolant temperature is attained.

Check display in display zone 3 (voltage supplied from modulating piston movement sender).

Read measured value block 1
⇒
840 rpm
6.5 mg/H
1.480 V
87.3 5C
Check voltage at modulating piston movement sender in display zone 3.
Specification: 1.45...2.00 V
If specification is not obtained, check modulating piston movement sender and metering adjuster as described in following:

Checking modulating piston movement sender (G149).

Press the ⇒key.
Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.

Switch off ignition.
Disconnect 10-pin connector for fuel temperature sender (connection to injection pump metering control).
Measure resistance between connector contacts 1 + 2 and 2 + 3.
Specification: 4.9 ... 7.5 ω

If the specification is not obtained:

Replace injection pump => Page
23-16
.

If the specification is obtained:

Connect test box V.A.G 1598/31 to control unit wiring harness.

Check wiring between test box and connector for open circuit according to current flow diagram.
Contact 1 + socket 108
Contact 2 + socket 106
Contact 3 + socket 99
Wire resistance: max. 1.5 ω
Additionally check wires for short to one another, to vehicle earth and to battery positive.
Specification: ∞ω

If no fault is detected in the pipes:

Renew Diesel direct injection system control unit (J248) => Page
23-108
.

Checking metering adjuster (N146)

Press the ⇒key.
Press keys 0 and 6 for the "End data transfer" function and confirm input with the Q key.

Switch off ignition.
Disconnect 10-pin connector for fuel temperature sender (connection to injection pump metering control).
Measure resistance between connector contacts 5 + 6.
Specification: 0.5...2.5 ω

If the specification is not obtained:

Replace injection pump => Page
23-16
.

If the specification is obtained:

Connect test box V.A.G 1598/31 to control unit wiring harness.

Check wiring between test box and connector for open circuit according to current flow diagram.
Contact 5 + sockets 1 and 2
Contact 6 + sockets 121 and 116
Wire resistance: max. 1.5 ω
Additionally check wires for short to one another, to vehicle earth and to battery positive.
Specification: ∞ω

If no fault is detected in the pipes:

Renew Diesel direct injection system control unit (J248) => Page
23-108
.