Checking the valve injectors (BMW 5 Series E39)

Valve injectors periodically inject fuel with a cone-shaped stream and close tightly after injection. Leaky valve injectors cause difficulties when starting a hot engine. Faulty valve injectors sometimes lead to spontaneous ignition of the working mixture in the cylinders and engine shutdown.

Unscrew the cover fastening above the valve injectors.

Leave the engine to idle.

With the engine running, use a stethoscope to check the operation of each injector valve. The opening and closing of the injector valve should be clearly audible.

If the stethoscope is missing, the valve can be felt by touching the nozzle with a screwdriver or finger.

If there is no noise from the valve operation or it is uncharacteristic, then it is necessary to check the supply voltage, winding resistance and the tightness of the valve injector.

Checking the supply voltage and resistance

Check the supply voltage. To do this, remove the plugs from the valve injectors and connect a semiconductor test lamp between both contacts of the supply wire. When the assistant turns on the starter, the test lamp should flash.

If the control lamp does not flash, the cause of the malfunction may be a break in the electrical circuit or the control unit itself.

Turn off the ignition.

Connect an ohmmeter to both contacts on the valve injector and measure the resistance. If the winding resistance of any injector does not correspond to the prescribed value, it must be replaced. The prescribed resistance value is 15-17 Ω.

If necessary, replace the faulty valve injector.

Checking for leaks

Remove the valve injectors. Leave the injectors and fuel lines connected to the fuel distribution manifold.

Place the plug cover with electrical connectors on the valve injectors.

Insert the valve nozzles into a suitable measuring vessel.

Ask an assistant to turn on the starter for a few seconds, while comparing the shape of the jets of the injectors with each other. The fuel should come out in a cone-shaped stream, the same for all the injectors.

Turn off the ignition.

Remove the plug cover from the valve injectors.

Turn on the ignition for about 5 seconds, do not turn on the starter. Check for leaks: after a minute, no more than one drop of fuel should appear on the nozzles of the valve injectors.

Install the injectors.

Note: At the BMW service station, the tightness of the removed valve injectors is checked with compressed air. Leaky injectors are repaired using a cleaning liquid on a special ultrasonic unit.