BMW 1 Quiz
Fuel and Exhaust Systems

Injector Testing

In this manual: Fuel and Exhaust Systems
Introduction — 10Owner's Manual — 29Routine Care and Maintenance — 30Engine — 18Cooling and Heating Systems — 13Fuel and Exhaust Systems — 29Engine Electrical Equipment — 20Manual Transmission — 4Automatic Transmission — 4Clutch and Drive Shafts — 12Brake System — 19Suspension and Steering — 22Body — 36Body Electrical Equipment — 34Electrical Circuit Diagrams — 30On-board diagnostic system — 5
~1min read

Injectors deliver fuel in pulses. The spray pattern is cone-shaped. After injection ends, the injector valve closes tightly. Leaking injectors cause difficulty starting a hot engine. Faulty injectors cause the engine to keep running for some time after it is switched off and cause misfiring.

CHECKING
1. Remove the injector cover.
2. Start the engine and let it idle.
3. With the engine running, listen to each injector with a stethoscope. The injector valves should click when opening and closing.
4. If no stethoscope is available, use a screwdriver or a finger.
5. If the noise is abnormal or absent, check the voltage, resistance and tightness of the injectors.

Checking Injector Voltage and Resistance

PROCEDURE
1. Check the voltage. Disconnect the injector connector and connect a diode test light between the supply wire terminals. Crank the engine with the starter. The LED should flash.
2. If the diode does not flash, the cause may be an open circuit in the wiring or a fault in the control unit.
3. Switch off the ignition.
4. Connect an ohmmeter between the two terminals on each injector and measure the resistance. If the resistance differs from the specified value, replace the injector. Resistance must be 15–17.5 ohms.
5. If necessary, replace the faulty injector.

Checking Tightness

PROCEDURE
1. Remove the injectors. Do not disconnect the fuel lines from the fuel rail.
2. Connect the plugs to the injectors.
3. Lower the injectors into a container.
4. Have an assistant crank the engine with the starter for several seconds. Compare the spray pattern of the injectors. The spray must be cone-shaped and identical for all injectors.
5. Switch off the ignition.
6. Disconnect the injector connector strip.
7. Switch on the ignition for 5 s without cranking the engine. Check tightness: no more than one drop should form within one minute.
8. Install the injectors.

* At BMW service centers, tightness is checked with compressed air. Leaking injectors are cleaned in an ultrasonic cleaner using cleaning agent.

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