A faulty cold start valve causes difficulty starting (cold and warm), dips in transient modes and high fuel consumption.
The thermal time switch limits the fuel injection time depending on the engine temperature.
Removal
Disconnect the plug from the cold start valve.
Unscrew the fuel line to the cold start valve.
Caution: The system is under pressure, so place a rag over the connection and slowly loosen the bolt. If the cold start valve is removed only for inspection, the fuel line remains connected.
Unscrew the cold start valve and remove it from the intake elbow.
Examination
Disconnect the central high-voltage cable - terminal 4 - from the ignition distributor and short it to ground. If necessary, use an auxiliary cable of the same cross-section.
Disconnect the plug from the thermal time switch.
Connect the green-white wire of the thermal time switch to ground using an auxiliary cable.
Caution: Do not short-circuit the black-red wire to ground. Possible short circuit!
Disconnect the plug from the cold start valve and connect it to the contacts of the voltmeter or indicator plug.
Turn on the starter, the indicator should show voltage. Otherwise, find and eliminate the break according to the diagram.
Engines 113/115/136 hp, designations 3A, AAD, NG
The injection time of the cold start valve is determined by the KE-Jetronic/-Motronic control unit depending on the engine temperature.
NG: Disconnect the plug from the coolant temperature sensor and short both contacts of the plug to ground through a 3 kOhm resistor. The valve injection stream should be cone-shaped, the injection time should be 2-3 seconds.
3A, AAD: Disconnect the coolant temperature sensor plug and connect both contacts of the plug through a 15 kOhm resistor. The injection stream should be cone-shaped, the injection time should be 8 seconds.
If the valve does not inject, disconnect the plug on the cold start valve and check the resistance between the contacts. Nominal value: 10 Ohm.
If the resistance of the valve is OK, connect the voltage indicator to the plug and turn on the starter. The indicator should light for 8 seconds. Otherwise, have the control device checked and replace it if necessary.
Connect the plug to the cold start valve, the fuel hose is connected.
Place the cold start valve into the measuring vessel.
Turn on the starter briefly. The injection stream should have the shape of a regular cone.
Wipe the vent nozzle.
Not a drop should come out of the valve within a minute. The outside of the valve should also be dry.
Installation
Install the cold start valve with a new seal and screw it on.
Connect the plug to the thermal time switch.
Put on the ignition wire - terminal 4-.
If removed, screw the fuel hose to the cold start hose with a torque of 10 Nm. Connect the plug.