Cold Start Enrichment (Cabriolet & Scirocco)

To ensure smooth running, the system supplies additional fuel to a cold engine by increasing differential pressure regulator current for a short period after starting and during warm up. A coolant temperature sensor provides control unit with temperature information. The starter provides an additional signal for after-start enrichment. After-start enrichment lasts approximately 40 seconds. Cold running enrichment decreases gradually as the engine warms up, finally reaching the normal warm running value.

To test either function, remove the harness connector from the coolant temperature sensor to simulate a cold engine. To check cold running enrichment, turn ignition on. Differential pressure regulator current should be 80 to 100 mA.

After-start enrichment is checked after operating the starter. To prevent engine from starting during test, disconnect ignition coil wire from center of the distributor cap and use a jumper wire to connect it to ground. Actuate starter 2 to 3 seconds, then leave the ignition on. The differential pressure regulator current should increase to more than 120 mA for 30 to 60 seconds and then return to the cold running value given above. When the test is incomplete, turn the ignition off. Reconnect coil wire and the coolant temperature sensor harness connector.

Test coolant temperature sensor by detaching its harness connector and checking resistance across the sensor's terminals. The correct resistance varies with engine coolant temperature. When replacing sensor, drain and refill coolant.