Passat L4-1984cc 2.0L DOHC (1991)
Cold Start Valve: Description and Operation
Component Locations
The cold start valve which is located in the intake manifold injects fuel for a limited period to aid the starting process.
Cold Start Valve Operation
The control of the cold start valve occurs according to a CIS-E Motronic control unit map based on coolant temperature that creates a pulsating injection
(duty cycle) of the cold start valve. Normal duty cycles range from 50% - 100%.
The cold start valve receives power whenever the ignition switch is in the "ON" or "RUN" position. The Motronic control unit determines how long the
valve is open by switching the ground side (duty cycle) of the circuit.
The Motronic control unit also operates the cold start valve to aid in hot starting if the coolant temperature is above approx. 239°F. In the event that the
engine does not run after approx. 2 seconds of starter operation the cold start valve will operate at a 10% duty cycle for seven to eight seconds.
If the cold start valve fails to inject fuel during cold starting, it will be difficult or impossible to start the engine.
