Note: With the Digifant system, the supply voltage and resistance for all valve injectors are checked at the common connector. With the Simos system, the check is performed for each injector separately. The tightness of the injectors and the shape of the fuel jet are checked in the same way in both cases. Removal of the valve injectors of the Simos system is carried out in accordance with Figure 24-0389 (see below).
Valve injectors do not inject all of the fuel at once, meaning that half of the fuel required to complete the working cycle is injected per revolution of the crankshaft.
The injector injects fuel in a cone-shaped stream and closes tightly after injection. Leaky injectors create difficulties when starting a hot engine. Injector defects cause spontaneous engine operation after the ignition is turned off and lead to its shutdown.
AFT engine: Remove upper intake manifold.
Checking the supply voltage and resistance
Digifant: Disconnect plug "1" of the valve injectors.
Simos: Disconnect the valve injector plug.
Connect a semiconductor diode test lamp to the plug. Ask an assistant to turn on the starter. The LED should blink.
Note: The ABF engine has a 5-pin plug. Pin 5 (opposite the locking bracket) connected to ground, contacts 1-4 are connected to individual valve injectors. Connect the test lamp in series between contact 5 and contacts 1-4
If the LED does not blink, the cause may be a faulty Hall sensor, a broken wire, or the control unit itself. Perform an electrical test of the injection system, see below.
Turn off the ignition.
Digifant: Measure the total resistance of all valve injectors on the plug connector "2". The prescribed resistance value is 3.7-5.0 Ohms.
Note: If the measured value does not correspond to the prescribed value, it is possible to draw a conclusion on how many valve injectors are defective depending on the measured value. If one injector is defective, the measured value should be 5.0-6.7 Ohm: if two injectors are defective, 7.5-10.0 Ohm; if three injectors are defective - 15.0-20.0 Ohm.
ABF Engine: Measure the resistance in series between terminal 5 and terminals 1-4. The prescribed resistance value is 15.0-20.0 ohms.
If the resistance at connector block "2" is greater than 5 ohms, remove the wire guide from the fuel distributor bracket and, as with AFT/ADY/AGG engines, perform an individual check of the valve injectors.
AFT/ADY/AGG engines: connect a test lamp between the contacts of a separate valve injector. The prescribed resistance value is 15.0-20.0 Ohm respectively.
If necessary, replace the valve injector.
Checking the jet shape and tightness (Digifant/Simos)
Disconnect the high-voltage wire from the ignition coil at the ignition distributor and connect it to ground; use an auxiliary wire if necessary.
Remove the air intake hose together with the idle speed stabilization valve, as well as the bracket and the crankcase ventilation pressure control valve. First loosen and move the fastening clamps back.
Disconnect plug "1" from the wire guide block.
Disconnect the wire guide "2" from the fuel distributor holders (arrows).
Unscrew bolts "3" and "4" securing the fuel distributor.
Unscrew the throttle valve pipe from the intake manifold by loosening the 4 Allen bolts at the flange.
Pull the valve injectors together with the fuel distributor and wire guide out of the exhaust manifold. The valve injectors are just inserted and can be easily removed.
Place the valve nozzles into a suitable measuring vessel.
Disconnect the blue temperature sensor plug at the coolant pipe.
Connect a 15 Ohm resistor between the contacts of the temperature sensor plug.
Connect plug "1" of the valve injector to the wire guide block "2".
Ask an assistant to turn on the starter for a few seconds and compare the shape of the fuel jets of the valve injectors. The fuel jets of all injectors should have the same conical shape.
Turn off the ignition.
Disconnect the plugs from the valve injectors.
Turn on the ignition for about 5 seconds, do not turn on the starter. Within one minute, no more than two drops of fuel should come out of the injector nozzles.
Install valve injectors.
Caution: When installing the injectors, ensure that the sealing rings are not damaged.
Check the rings for damage, replace the rings if necessary. Moisten the sealing rings with fuel before installation.
Install the fuel distributor, wire guide and inlet hoses in the reverse order. Secure the hoses with clamps and tightening screws.
Screw the throttle valve pipe to the intake manifold, not forgetting to install the sealing gasket. Tighten the 4 Allen bolts with a torque of 20 Nm using a cross pattern.
Connect the high voltage wire to the ignition coil.
The information is posted on this website [www.VWMANUAL.ru]
AFT Engine: Install upper intake manifold.
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