Economic Driving (Economy)

Testing economy driving gauge




- Disconnect vacuum line at distributor (arrow).
- Connect tester 201 589 13 21 00 to vacuum line at intake manifold.
- Start engine.
Specification at idling speed: -0.4 to -0.6 bar. If the specification is not achieved, the vacuum line is fouled or leaking; clean or replace as necessary.
- Connect tester 201 589 13 21 00 between intake manifold and gauge.
- Gauge pointer moves to the left (1), specification at left stop: >= -0.585 bar.
- Increase idle speed until pointer of gauge is at start of red field (2).
Specification: approx. 0.4 bar.
- If specified value or reading on gauge not reached check for leak in vacuum system of headlamp range control and/or air conditioner.

Note: If a faulty vacuum unit at the transmission is found on vehicles with automatic transmission, oil may also be present in the gauge and in the cable. Clean cable and replace gauge.

- Disconnect tester 201 589 13 21 00.

Special Tool:

Function



The gauge is connected by a vacuum line to the intake manifold and indicates the momentary fuel consumption as a function of intake manifold vacuum. At a high intake manifold vacuum the pointer is in the black field of the gauge (low fuel consumption); as intake manifold vacuum drops, the pointer moves into the red field. The momentary fuel consumption increases.

When the engine is not running, the pointer is in the red field against the right stop pin.





Note: The pointer only indicates a reading at a vacuum of >= 0.08 bar.

Note:
If the pointer remains in the red field against the right stop, there is a leak in the vacuum line to the gauge (connection point, line) or the gauge is faulty.

Replace vacuum line and/or gauge.

If the gauge is very sluggish, the cause may be oil in the vacuum line and/or in the instrument. Oil can get into the vacuum system as a result of a faulty membrane in the vacuum unit at the automatic transmission, and this may cause failure of the gauge.