Injectors — checking (BMW 7 Series E32)

The injectors inject fuel in portions. The fuel stream from the injector has a cone shape, and the injector closes tightly after injection. Leaky injectors create difficulties when starting a hot engine. Faulty injectors cause the engine to run after the ignition is turned off, which leads to damage.

Unscrew the bolts and remove the cover above the nozzle.

The engine should be idling.

Using a stethoscope, check each injector on a running engine to see if there are any clicks when it operates. These clicks correspond to the opening and closing of the injector.

If you don't have a stethoscope, you can check the operation of the injector by placing a screwdriver or even your finger on it.

If there is no noise from the injectors or they are unusual, then you need to check the voltage supply, resistance and density of the injectors.

Checking the voltage supply and resistance

Check the voltage supply. To do this, remove the injectors and connect a test lamp (LED) between the plug contacts. The assistant should turn on the starter, and the LED should blink.

If the LED does not blink, the fault may be in the wires or in the control unit itself.

Turn off the ignition.

Connect an ohmmeter to the terminals of each injector and measure the resistance. If the resistance of one or more injectors differs from the required (15 -17.5 Ohm), then it (they) need to be replaced.

Replace the injector if necessary.

Density test

Remove the injectors. The valves and fuel lines remain connected to the fuel rail.

Install the electrical connections (bar) on the injectors.



Place the nozzles in suitable measuring containers.

The assistant should turn on the starter for a few seconds. While it is running, compare the shape of the fuel stream from different injectors. It should be approximately the same for all injectors and have the shape of a cone.

Turn off the ignition.

Remove the electrical connections from the injectors.

Turn on the ignition for about 5 seconds without turning on the starter, then check the density: no more than one drop of fuel should come out of the injectors in 1 minute.

Install the injectors.

Note: In specialized workshops, the tightness of the removed injectors is checked using compressed air. Leaky injectors are cleaned in a special ultrasonic device using a special cleaning liquid.