Disconnect the green control wire from the ignition.
Remove the air filter.
Checking the supply voltage
Disconnect the coolant temperature sensor plug.
Remove the cold start valve plug (98). Measure the voltage between the black and pink wire of the connector and the ground of the engine block with a voltmeter.
Turn on the starter. If the voltage is approximately 10 V, remove and check the cold start valve. Otherwise, according to the diagram, check for a break in the wire circuit between the cold start valve and the fuel pump relay, respectively, between socket 2 on the relay board and terminal 9 of the control unit. Replace the wire if necessary.
If no fault is found, connect a voltmeter between socket 12 (terminal 50) on the relay board and ground. When the starter is running, this voltage should be approximately 10 V. In this case, replace the fuel pump relay, otherwise eliminate the open circuit according to the diagram.
Checking the cold start valve
Relieve excess pressure in the fuel system.
(Original published on the website: MercedesMan.ru)
The temperature sensor wire remains disconnected, the fuel pump relay is in place.
Unscrew the cold start valve fuel line.
Unscrew the cold start valve, screw the fuel line onto it and lower the valve into the measuring cup.
Install the cold start valve plug.
Remove the fuel pump relay and short-circuit contacts 1 and 2. Connect to the battery terminal.
The valve should spray the fuel in a uniform cone.
Dry the valve sprayer.
There should not be a drop of gasoline on it for a minute.
Put on the temperature sensor plug.
Install the cold start valve with a new gasket, tighten the fuel line with a force of 10 Nm.
Connect the green ignition control wire.
Install an air filter.