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Hyundai Coupes/Sedans 1986-1993 Repair Guide

Diagnosis And Testing


See Figures 1

If the FBC system components (sensors, carburetor control unit computer, solenoid, etc.) fail, interruption of the fuel supply or failure to supply the proper amount of fuel for engine operating conditions will result.

This condition will have several effects on the system: The engine will be hard to start or will not start at all, The engine idle will be unstable or poor performance will occur. If any of the above conditions are noted, first perform basic engine checks (ignition system malfunctions, incorrect engine adjustment, etc.).

If the basic engine checks show no faults, the FBC system can be checked by the use of FBC checker as follows:

Before disconnecting the battery terminals, make sure the ignition switch is in the OFF position. If the battery terminals are disconnected while engine is running or when ignition switch is in the ON position, malfunction or damage of the ECU could result. Disconnect the battery cables before charging the battery. When battery is connected, be sure not to reverse polarity. Make sure all electrical harness connectors are securely connected. Be careful not to allow entry of water or oil into connectors.

  1. Turn ignition switch to the OFF position.
  3. Remove the harness connector A (13 poles) and connector B (7 poles) from carburetor computer control unit.
  5. Set the check switch of the FBC checker to the OFF position. Set the select switch of checker tool to the A position.

Click image to see an enlarged view

Fig. Fig. 1: Feedback carburetor checker tool wiring harness

  1. Connect the FBC harness connector to the connectors of FBC checker tool. Connect the FBC harness connectors and place FBC checker tool on front seat of the vehicle.
  3. If the checker tool shows any departure from specifications, check the corresponding sensor and related electrical wiring. Repair or replace defective components as required.
  5. After repair or replacement, check the system to confirm that repaired or replaced part is performing properly.
  7. If the problem is still not corrected and the control unit appears to be at fault, perform all checker tests and individual sensor tests again. If everything is in order, replace the carburetor control unit.