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Injector Quantity Comparison

  1. Remove fuel pump relay, from relay panel, and install Jumper Switch (US 4480/3). Attach Fuel Quantity Analyzer (US 4480) to bumper and secure in place. Remove injectors from cylinder head with fuel lines attached. Check and replace fuel injector "O" rings as necessary.
  2. Check tightness of injector insert (2-piece inserts). If inserts are loose, remove and clean threads. Use sealing compound when installing upper insert. Replace sealing washer against cylinder head below lower portion of insert. Lubricate injector "O" rings with gasoline and install injectors with fuel lines connected, into fuel quantity analyzer tubes.
  3. Ensure lines are not kinked or bent. Loosen fittings to align fuel lines and retighten. Remove rubber boot from airflow sensor housing above sensor plate. Turn and lift setting screw and adjusting slide of Sensor Plate Adjustable Holder (VW 1348/1) into upper position. This simulates full throttle operation. See Fig 1 .
    Fig 1: Sensor Plate Adjustable Holder (VW 1348/1)
    G94326Courtesy of AUDI OF AMERICA, INC.
  4. Place sensor plate adjustable holder on airflow sensor housing with holder centered over plate. Pointer on edge of holder base must point toward center of fuel distributor. See Fig 1 . Push adjusting slide of holder down onto stop.
  5. Turn adjusting screw clockwise until magnetic end touches sensor plate retaining bolt. Activate fuel pump with jumper switch. Turn adjusting screw of holder counterclockwise until any one injector starts to deliver fuel. Turn off jumper switch and empty fuel quantity analyzer into fuel tank.
  6. Idle injection quantity is measured first. Lifting adjusting slide of holder to first stop simulates idle position of sensor plate. Activate fuel pump with jumper switch until fuel level reaches 20 ml on scale of any tube for quantity comparison.
    NOTE: The abbreviation "ml" stands for milliliters.
  7. Check that all injectors have identical spray patterns that are even and cone-shaped. If not, raise sensor plate up quickly to full lift position and release. Repeat idle quantity test. Maximum difference in delivery quantity between injectors is 3.0 ml of fuel.
  8. If fuel delivery quantity differs between high and low levels by more than 3.0 ml, interchange injectors and repeat test. If difference of delivery quantity changes with injectors, replace injectors. If difference of delivery quantity does not change with movement of injectors, either fuel lines are pinched or fuel distributor is defective.
  9. Measure full throttle injection quantity. Empty analyzer into fuel tank and reinstall injectors in analyzer. Lift adjusting slide of holder to last stop to simulate full throttle position of sensor plate. Activate fuel pump with jumper switch until fuel level reaches 80 ml on scale of any tube of analyzer.
  10. Check that all injectors have identical spray patterns that are even and cone-shaped. Maximum difference in delivery quantity between injectors is 8.0 ml of fuel.
  11. If fuel delivery quantity differs between high and low levels by more than 8.0 ml, interchange injectors and repeat test. If difference of delivery quantity changes with injectors, replace injectors. If difference of delivery quantity does not change with movement of injectors, either fuel lines are pinched or fuel distributor is defective.
  12. Check fuel injectors for leakage immediately after delivery quantity test is complete. Set sensor plate in rest position. Activate fuel pump with jumper switch for 2 minutes. Injectors should not drip. Replace injectors that do drip.
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