Fuel Injection System Operation Check

PROCEDURE


See the warnings at the beginning of the Fuel System Pressure Relief section.
1. Check the security of electrical connections, especially the ground terminals of the injection circuit. Carefully inspect all electrical connectors related to system operation. Poor electrical contact causes many problems and is the cause of more than half of engine failures.
2. Check the battery charge level. The accuracy of air-fuel mixture control depends largely on the proper operation of the PCM and information sensors, which is determined, among other things, by their supply voltage level.
3. Check the condition of the air cleaner filter element. Even partial restriction of the air filter has a significant effect on fuel economy and engine output (see Chapter Maintenance and Tune-Up).
4. Check the operation of the fuel pump (see section Fuel Pump Operation Check, Fuel Pressure Measurement). If the pump fuse has blown, replace it with a new one. If the new fuse also blows immediately, check the circuit wiring for signs of a short circuit (see Chapter Body Electrical).
5. Check the condition of the vacuum hoses connected to the intake manifold.
6. Disconnect the air duct from the throttle body and inspect the throttle body for carbon buildup and other deposits (especially in areas near the throttle plate). If signs of contamination of the throttle body are found, refer to the Engine Controls chapter and diagnose the PCV and EGR systems. If heavily contaminated, the throttle body must be replaced.

The throttle bore walls, throttle plate and its shaft on these vehicle models are covered with a protective film, which should not be removed in order to avoid accidental damage to components.

7. With the engine running, listen to each fuel injector in turn using a stethoscope. Even clicking indicates that the injector is operating properly. If a stethoscope is not available, use a long screwdriver, pressing the tip against the injector body and noting the vibrations transmitted through the handle.

8. If fuel injector malfunction is suspected, use a special injector test light (available at automotive accessory stores). The light is connected to the electrical connector of the suspect injector. Start the engine and check all injectors with the light. A steady flashing of the light confirms that the injector is operating properly. Otherwise, take the vehicle to a service station for further diagnosis.

9. Turn off the engine, disconnect the injector electrical connectors and measure the electrical resistance of each injector. Compare the measurement results with the Specifications. If necessary, replace the faulty component.

10. Additional information on diagnosing the injection system is provided in the Engine Controls chapter.