Testing Start Valve Actuation

Testing start valve actuation

Preceding work:
Testing starting device. Testing Start Device





- Connect testers:
- multimeter (003)
- ohms decade (038)124 589 09 63 00.
- Test starting voltage. At least 10 V in approx. 5 seconds.
- Test electric wiring between starting valve and fuel pump relay for continuity. Resistance approx. 0 ohm.
- a) Vehicles with actuation via thermo-time switch (S26)
- Test thermo-time switch (S26) (102.961 USA).
- b) Vehicles with actuation via fuel pump relay module
- Test voltage at fuel pump relay module. Contact 12 (terminal 50) at least 10 V, contact 2 (terminal TF).

Special Tools:

Commercially Available Tester:

a) Vehicles with actuation via thermo-time switch (arrow)

The start valve is operated by the closed thermo-time switch only when the engine coolant temperature is below +5°C.

The actuation time increases as the temperature drops and reaches approx. 12 seconds at -20°C.

Test below + 5°C engine coolant temperature

Remove thermo-time switch and cool with commercially available refrigerant.

Connect voltmeter to terminal of start valve (Y8).

Operate starter. Depending on the engine coolant temperature, the voltmeter must then indicate >=10 volts over a certain period.

The switching time increases as the temperature drops by approx. 1.5 seconds per 5°C.
e.g. +5°C = 0 seconds
0°C = 1.5 seconds

It is recommended to still test the thermo-time switch (S26) with an ohmmeter for this test.

Test value below +5°C:
Terminal W-G approx. 93 ohm (contacts in switch closed).

Test above + 5°C engine coolant temperature

Above an engine coolant temperature of +5°C the test of the thermo-time switch (S26) can only be performed with an ohmmeter. Unplug the connector at the thermo-time switch for this step.

Test value above +5°C:
Terminal W-G infinite ohm (contacts in switch open).

b) Vehicles with actuation via fuel pump relay

Depending on the engine coolant temperature the start valve is actuated by the coolant pump relay.

Example:
-20°C=10 seconds.
No further actuation occurs above +60°C or +15°C, respectively.

Key To Symbols:

Test Steps 1.0:

Test Steps 1.0 - 2.0:

Test Steps 3.0 - 5.0:

Resistances Of Engine Coolant Temperature Sensor (B11/2):