Hyundai Coupes/Sedans 1986-1993 Repair Guide

Fuel Injectors

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See Figures 1 through 5

Fuel injectors are injection nozzles with solenoid valves. They're responsible for injecting fuel into the intake manifold at precisely the right instant based on signals from the engine's electronic control unit (ECU).



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Fig. Fig. 1: Fuel injector and delivery pipe-4 cylinder engine Sonata



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Fig. Fig. 2: Fuel injector installation on all engines



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Fig. Fig. 3: Fuel pressure regulator positioning on Sonata

REMOVAL & INSTALLATION



1596cc, 1796cc and 1997cc Engines
  1. Relieve the fuel system pressure.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Wrap the connection with a shop towel and disconnect the high pressure fuel line at the fuel rail.
  6.  
  7. Disconnect the fuel return hose.
  8.  
  9. Disconnect the vacuum hose from the fuel pressure regulator. Remove the fuel pressure regulator and O-ring.
  10.  
  11. Disconnect and remove the PCV hose.
  12.  
  13. Label and disconnect the electrical connectors from each injector.
  14.  
  15. Remove the injector rail retaining bolts. Make sure the rubber mounting bushings do not get lost.
  16.  
  17. Lift the rail assembly up and away from the engine.
  18.  
  19. Remove the injectors from the rail by pulling gently. Discard the lower insulator. Check the resistance through the injector. The specification is 13-16 ohms at 70°deg;F (20°deg;C). If resistance is out of desired reading, replace the injector.
  20.  

To install:
  1. Install a new grommet and O-ring to the injector. Coat the O-ring with light oil.
  2.  
  3. Install the injector to the fuel rail turning to the left and right during installation.
  4.  
  5. Install the fuel rail and injectors to the manifold. Make sure the rubber bushings are in place before tightening the mounting bolts.
  6.  
  7. Tighten the retaining bolts to 72 inch lbs. (11 Nm).
  8.  
  9. Connect the electrical harness connectors to the injectors. Install and connect the PCV hose.
  10.  
  11. Replace the O-ring, lightly lubricate it and connect the fuel pressure regulator.
  12.  
  13. Connect the fuel return hose.
  14.  
  15. Replace the O-ring, lightly lubricate it and connect the high pressure fuel line.
  16.  
  17. Connect the negative battery cable and check the entire system for proper operation and leaks.
  18.  

1468cc, 1495cc and 2351cc Engines
  1. Relieve the fuel system pressure.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Disconnect and remove the air intake hoses as required.
  6.  
  7. Wrap the connection with a shop towel and disconnect the high pressure fuel line at the fuel rail.
  8.  
  9. Disconnect the fuel return hose.
  10.  
  11. Disconnect the accelerator cable connection from the throttle body and position aside.
  12.  
  13. Disconnect the vacuum connection from the fuel pressure regulator.
  14.  
  15. Disconnect the electrical harness connector from each fuel injector.
  16.  
  17. Remove the injector rail retaining bolts. Make sure the rubber mounting insulators do not get lost.
  18.  
  19. Lift the rail assembly up and away from engine.
  20.  
  21. Remove the injectors from the rail by pulling gently. Discard the lower insulator. Check the resistance through the injector. The specification is 13-16 ohms at 70°deg;F (20°deg;C).
  22.  

To install:
  1. Install a new grommet and O-ring to the injector. Coat the O-ring with light weight oil.
  2.  
  3. Install the injector to the fuel rail.
  4.  
  5. Install the fuel rail and injectors to the manifold. Make sure the rubber bushings are in place before tightening the mounting bolts.
  6.  
  7. Tighten the retaining bolts to 9 ft. lbs. (12 Nm).
  8.  
  9. Connect the electrical connectors to the injectors.
  10.  
  11. Replace the O-ring on the fuel pressure regulator, lightly lubricate and install on the delivery pipe. Connect the vacuum hose to the fuel pressure regulator.
  12.  
  13. Connect the fuel return hose.
  14.  
  15. Replace the O-ring on high pressure fuel line, lightly lubricate it and connect to delivery pipe.
  16.  
  17. Reconnect the accelerator cable to the throttle body and adjust to specifications.
  18.  
  19. Connect the negative battery cable and check the entire system for proper operation and leaks.
  20.  

2972cc Engine
  1. Relieve the fuel system pressure.
  2.  
  3. Disconnect the negative battery cable.
  4.  
  5. Drain the cooling system.
  6.  
  7. Disconnect all components from the air intake plenum and remove the plenum from the intake manifold. Discard the gaskets.
  8.  
  9. Wrap the connection with a shop towel and disconnect the high pressure fuel line at the fuel rail.
  10.  
  11. Disconnect the fuel return hose and remove the O-ring.
  12.  
  13. Disconnect the vacuum hose from the fuel pressure regulator. Remove the fuel pressure regulator and O-ring.
  14.  
  15. Disconnect the electrical connectors from each injector.
  16.  
  17. Remove the injector rail retaining bolts. Make sure the rubber mounting bushings do not get lost.
  18.  
  19. Lift the rail assemblies up and away from the engine.
  20.  
  21. Remove the injectors from the rail by pulling gently. Discard the lower insulator. Check the resistance through the injector. The specification is 13-16 ohms at 68°deg;F (20°deg;C).
  22.  

To install:
  1. Install a new grommet and O-ring to the injector. Coat the O-ring with light oil.
  2.  
  3. Install the injector to the fuel rail.
  4.  
  5. Replace the seats in the intake manifold, if equipped. Install the fuel rails and injectors to the manifold. Make sure the rubber bushings are in place before tightening the mounting bolts.
  6.  
  7. Tighten the retaining bolts to 72 inch lbs. (11 Nm). Install the fuel pipe with new gasket.
  8.  
  9. Connect the electrical connectors to the injectors.
  10.  
  11. Replace the O-ring, lightly lubricate it and connect the fuel pressure regulator.
  12.  
  13. Connect the fuel return hose.
  14.  
  15. Replace the O-ring, lightly lubricate it and connect the high pressure fuel line.
  16.  
  17. Using new gaskets, install the intake plenum and all related items. Torque the plenum mounting bolts to 13 ft. lbs. (18 Nm).
  18.  
  19. Fill the cooling system.
  20.  
  21. Connect the negative battery cable and check the entire system for proper operation and leaks.
  22.  

TESTING



Removal of the fuel injectors is not necessary to test them. To test the injectors you will need an engineer's stethoscope and an ohmmeter.



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Fig. Fig. 4: Checking for injector operating sound with a stethoscope

Operating Sound Check

The sound check is performed to check for an injector(s) that is not working. To check operating sound, have an assistant start the engine and operate the gas pedal. With an engineer's stethoscope touching the injector body, listen for the operating sound at idle speed. You should hear a distinct "ticking" sound at a steady interval as the solenoid valve opens and closes. Listen to all four injectors. Have the assistant increase the engine speed and listen again. The ticking interval should increase in proportion to the increase in engine speed. Again, perform this test on all injectors.

Sometimes the sound from an adjacent injector will be transmitted to another injector across the delivery pipe. In this case a bad injector will appear to be working fine. To avoid this, make sure the tip of the stethoscope is placed directly on the injector body and does not bridge the delivery pipe.



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Fig. Fig. 5: Measuring injector resistance

Resistance Check

To measure injector resistance, disconnect the electrical connector from the injector and place the probes of the ohmmeter across the injector terminals. Set the ohmmeter to the x1 range and check the resistance. It should be 13-16 ohms. Connect the injector connector and move on to the next injector. If the resistance reading is not as specified, replace the injector.

 
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