Circuit/System Testing

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.

Ignition ON, command the fuel pump relay ON with a scan tool and observe the fuel pressure while the fuel pump is operating. Verify the fuel pressure is between 380-410 kPa (55-60 psi).
- If the fuel pressure is more than the specified range, replace the fuel pump.
- If the fuel pressure is less than the specified range, remove the fuel tank and test/inspect for the following:
  - Restricted fuel feed pipe
  - Restricted or plugged fuel filter
  - Restricted or plugged strainer
  - Stuck or binding fuel level float
  - Restricted siphon jet pump
  - Restricted transfer lines between fuel tanks
  - Faulty fuel pressure regulator
  - Poor connections at the harness connectors and ground circuits of the fuel pump
- If you find a condition, repair as necessary.
- If all components test normal, replace the fuel pump.

IMPORTANT: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.

Verify that the fuel pressure does not decrease more than 34 kPa (5 psi) in 1 minute.
- If the fuel pressure decreases more than the specified value, perform the following procedure:
  1. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief (With CH 48027 - LP1, LY7) or Fuel Pressure Relief (Without CH 48027 - LP1, LY7) or Fuel Pressure Relief (With High Pressure Pump - LLT) .
  2. Install the J 37287 between the fuel feed pipe and the fuel rail. See Special Tools .
  3. Open the valve on the J 37287 . See Special Tools .
  4. Bleed the air from the fuel pressure gage.
  5. Close the valve on the J 37287 . See Special Tools .
  6. Verify that the fuel pressure does not decrease more than 34 kPa (5 psi) in 1 minute.
    - If the fuel pressure remains constant, replace the fuel pump.
    - If the fuel pressure drops, locate and replace the leaking fuel injector.
Relieve the fuel pressure to 69 kPa (10 psi). Verify that the fuel pressure does not decrease more than 14 kPa (2 psi) in 5 minutes.
- If the fuel pressure decreases more than the specified value, replace the fuel pump.
Remove the J 37287 and CH-48027 . See Special Tools . Refer to Fuel Pressure Gage Installation and Removal (LP1, LY7) .
Operate the vehicle within the conditions of the customer concern while monitoring fuel related parameters with a scan tool.
- If the scan tool parameters indicate a lean condition, test/inspect for the following:
  - Restricted fuel feed pipe
  - Restricted fuel filter
  - Restricted siphon jet pump
  - Restricted transfer lines between fuel tanks
  - Faulty fuel pressure regulator
  - Poor connections at the harness connectors and ground circuits of the fuel pump
- If all components test normal and the scan tool parameters indicate a lean condition, replace the fuel pump.