Leave the engine to idle.
With the engine running, use a stethoscope to check each injector for valve operating noises. Valve clicks mean that the valve opens and closes.
If a stethoscope is not available, the operating noises of the injector valve can be felt with a screwdriver or finger.
If there are no noises or they are uncharacteristic, it is necessary to check the supply voltage on the injectors, their resistance and tightness.
Checking the supply voltage and resistance
Check supply voltage. To do this, disconnect the plug connector of the valve injector and connect a semiconductor diode test lamp to the contacts of the supply cable plug. Ask an assistant to turn on the starter. The control lamp should flash.
If the control lamp does not blink, then a broken wire or the control unit itself may be the cause of the malfunction.
Switch off the ignition.
Connect an ohmmeter between the terminals of each valve injector and measure the resistance. If the resistance of any injector differs from the other values, replace the defective valve injector.
Leak test
Remove the fuel manifold complete with valve injectors and attached fuel hoses.
Connect the plug connectors of the valve injectors.
Insert valve nozzles into a suitable measuring container.
Ask an assistant to turn on the starter for a few seconds. Valve injectors must intermittently inject fuel in accordance with the firing order of the cylinders. Compare the shape of the fuel jets valve injectors. The jet of fuel from all nozzles must have the same conical shape.
Switch off the ignition.
Disconnect the plug connectors of the valve injectors.
Turn on the ignition for about 5 seconds, do not turn on the starter. Now check the tightness: within one minute, no more than one drop of fuel should come out of the injector nozzles.
Install valve injectors.
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