Servo Removal
Remove the air filter.
Disconnect the servo connector.
Disconnect the vacuum and atmospheric valve hoses from the servo.
Disconnect the idle switch connector.
Remove the servo from the carburetor by unscrewing the three fastening nuts (to facilitate this operation, you can first remove the carburetor from the engine).
Leak test
Apply 12V to the plug «2» servo connector and connect to «mass» plug «3» connector; at the same time, the contacts of the vacuum valve open.
Connect tester (in ohmmeter mode) to plugs «4» And «7» servo connector.
Connect the hand vacuum pump hose to the «A» servo and create vacuum (the push rod of the servo drive moves in), at which the tester will show a resistance of 500-700 ohms.
Disconnect from plug «3» servo connector «mass» the wire; while the contacts of the vacuum valve are closed.
Disconnect the vacuum pump hose from the nozzle «A» servo. If the resistance value increases by more than 200 ohms within 1 minute, replace the servo.
Checking the stroke length and duration of retraction of the servo pusher
Apply a constant negative pressure of approx. 250 mbar to the connection using a hand vacuum pump «A» servo.
Apply 12V to the plug «2» servo connector and connect to «mass» plug «3» connector. In this case, the pusher of the servo drive must quickly move in (no more than 1 s).
Disconnect the electrical wires and the vacuum pump hose from the servo drive.
measure distance (see photo) between the end of the servo housing and the end of the idle switch (in a free position), which should be within 56.8-59.2 mm.
If the duration or length of the pusher retraction stroke is not correct, replace the servo.
Apply 12V to the plug «2» servo connector and connect to «mass» plug «8» connector. In this case, the pusher of the servo drive should move forward within no more than 1 s.
measure distance (see photo) between the end of the servo housing and the end of the idle switch (in a free position), which should be within 69.5-71.5 mm.
If the duration or length of the stroke of the extension of the pusher is not correct, replace the servo.
Checking the idle switch
Connect tester (in ohmmeter mode) to the plugs of the idle switch connector and measure the resistance, which should be 9 ohms when the switch is closed, and R = ∞ when the switch is opened.
Checking vacuum and atmospheric valves
Connect tester (in ohmmeter mode) to plugs «2» And «3» servo connector and measure the resistance of the vacuum valve winding. Then connect the tester to the plugs «2» And «8» servo connector and measure the resistance of the atmospheric valve winding. In both cases, the resistance value should be in the range of 35-80 ohms.
Potentiometer test
Connect tester (in ohmmeter mode) to plugs «4» And «5» servo connector and check the total resistance of the potentiometer, which should be between 1.3-2.5 kΩ.
Connect tester to terminals «4» And «7» servo connector and measure the resistance with the servo pusher extended, which should be between 0.9-1.9 kOhm.
Slowly slide the servo pusher in and measure the resistance of the potentiometer, which should be between 0-500 ohms.
If the resistance values are not within the specified limits, replace the servo.
Servo Installation
Installation of the servo is carried out in the reverse order of removal. If necessary, adjust the servo, replace the idle stop screw.