GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Monte Carlo 🢒 Engine 🢒 Engine Controls - 3.1L 🢒 Fuel Injector Replacement

Removal Procedure

Notice: Use care in removing the fuel injectors in order to prevent damage to the fuel injector electrical connector pins or the fuel injector nozzles. Do not immerse the fuel injector in any type of cleaner. The fuel injector is an electrical component and may be damaged by this cleaning method.

Important: Important the fuel injector is serviced as a complete assembly only. If the fuel injectors are found to be leaking, the engine oil may be contaminated with fuel.


    Object Number: 12687 Size: SH
  1. Relieve fuel system pressure. Refer to Fuel Pressure Relief .
  2. Remove the upper intake manifold. Refer to Intake Manifold Replacement .
  3. Remove the fuel rail. Refer to Fuel Injection Fuel Rail Assembly Replacement .
  4. Remove the fuel injector retaining clips (2).
  5. Remove the fuel injectors (3).
  6. Remove the fuel injector Upper O-ring (1).
  7. Remove the fuel injector lower O-ring (5).
  8. Remove the fuel injector lower O-ring Backup (4).

Installation Procedure

Important: When ordering new fuel injectors, be sure to order the correct injector for the application being serviced.

The upper and lower fuel injector O-rings use different part numbers. To identify the correct O-ring, the upper O-ring is black and the lower O-ring is brown. Both O-rings are the same size but consist of different material.

The fuel injector lower O-ring uses a nylon collar, called the O-ring backup, to properly position the O-ring on the injector. Always reinstall the O-ring backup, or the sealing O-ring may move on the injector when installing the fuel rail and result in a possible vacuum leak.

Fuel injector O-rings should always be replaced whenever fuel injectors are serviced


Object Number: 12639 Size: SH

The fuel injector assembly (1) is stamped with a part number identification (2) and a build date code (3). The build date code consists of the month (4) 1-9 (Jan-Sept) O, N, D, (Oct, Nov, Dec), day (5), and year (6).


    Object Number: 12687 Size: SH
  1. Install the fuel injector Upper O-ring (1).
  2. Install the fuel injector lower O-ring Backup (4).
  3. Install the fuel injector lower O-ring (5).
  4. Install the fuel injector (3) to fuel rail.
  5. Install the fuel injector retaining clips (2).
  6. Reinstall the fuel rail. Refer to Fuel Injection Fuel Rail Assembly Replacement .
  7. Reinstall the upper intake manifold. Refer to Intake Manifold Replacement .
  8. Reinstall the fuel filler cap.
  9. Inspect for fuel leaks through the following steps:
  10. Connect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection in engine electrical.
  11. Inspect for fuel leaks
    12. 11.1. Turn the ignition switch ON for 2 seconds.
    11.2. Turn the ignition switch OFF for 10 seconds.
    11.3. Turn the ignition switch ON.
    11.4. Check for fuel leaks.