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Home >> Cadillac >> 2010 >> Escalade EXT >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Control System & Fuel System - 5.3L, 6.0L, 6.2L - Troubleshooting & Diagnosis >> Fuel System Diagnosis (w/o FPCM) >> Circuit/System Testing
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Circuit/System Testing

    IMPORTANT:
    • The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.
    • DO NOT start the engine.
  1. Ignition ON, command the fuel pump relay ON with a scan tool and observe the fuel pressure gauge while the fuel pump is operating. Verify the fuel pressure is between 345-414 kPa (50-60 psi).
    • If the fuel pressure is greater 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, and repair the items listed below. If all items test normal, replace the fuel pump.
      • Restricted fuel feed pipe
      • Restricted or plugged fuel filter
      • Restricted or plugged strainer
      • Stuck or binding fuel level float
      • Inspect the harness connectors and the ground circuits of the fuel pump for poor connections.
    2. 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.
  2. 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 (CH-48027) or Fuel Pressure Relief (Without CH-48027) .
      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. Ignition ON, command the fuel pump relay ON with a scan tool and bleed the air from the fuel pressure gauge.
      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 drops, locate and replace the leaking fuel injector.
      7. If the fuel system test normal, replace the fuel pump.
  3. 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.
  4. Remove the J 37287  and CH-48027  . See Special Tools . Refer to Fuel Pressure Gauge Installation and Removal .
  5. Operate the vehicle within the conditions of the customers concern while monitoring the fuel trim and O2 parameters with a scan tool. The scan tool parameters should not indicate a lean condition.
    • If the scan tool parameters indicate a lean condition, test for a restricted fuel feed pipe, restricted fuel filter, or poor connections at the harness connectors and ground circuits of the fuel pump. If all test normal, replace the fuel pump.
  6. If the fuel system components test normal, refer to Symptoms - Engine Controls .
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