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Home >> Chevrolet >> 2020 >> Express 2500 LS, 6.0L Eng VIN G >> Repair and Diagnosis >> External Pages >> Different car >> Section 104 (Engine Controls And Fuel - 6.0L (L96 LC8) - Diagnostic Information And Procedures (2 Of 2)) >> Diagnostic Information and Procedures >> Fuel System Diagnosis (Without FPCM) >> Circuit/System Verification

Circuit/System Verification

WARNING: This page is about a different car, the 2019 GMC Savana 3500, 2019 GMC Savana 2500, 2019 Chevrolet Express 3500, and 2019 Chevrolet Express 2500. However, it is still accessible from the selected car via links, so may be relevant.
    NOTE:
    • Repair all fuel system related DTCs before performing this diagnostic, unless instructed here from a DTC.
    • Inspect the fuel system for damage or external leaks before proceeding.
    • Verify that adequate fuel is in the fuel tank before proceeding.
    • The Fuel Pump Enable may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.
    • DO NOT perform the Fuel System Diagnosis if the engine coolant temperature is above 60°C (150°F). High fuel pressure readings may result due to hot soak fuel boiling. With the engine OFF, the fuel pressure may increase beyond the pressure relief regulator valve's setting point of 550 kPa = / -5 % (80 PSI ±5 %).
  1. Ignition OFF, relieve the fuel pressure, refer to Fuel Pressure Relief . Install the CH - 37287 - 1A  Fuel Pressure Gauge Adapter and CH-48027  Digital Fuel Pressure Gauge to the fuel rail side of the adaptor. Refer to Fuel Pressure Gauge Installation and Removal .
  2. Ignition ON, verify the shut off valve is open on the CH - 37287 - 1A  Fuel Pressure Gauge Adapter, command the Fuel Pump Enable On with a scan tool. Verify the fuel pressure is between 345 - 551 kPa (50 - 80 PSI).
    • If the fuel pressure is less than 345 kPa (50 PSI) 

      Refer to Circuit/System Testing - Fuel Pressure Low.

    • If the fuel pressure is greater than 551 kPa (80 PSI) 

      Replace the G12 Fuel Pump.

    • Go to next step: If the fuel pressure is between 345 - 551 kPa (50 - 80 PSI) 
    3. NOTE:

    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.

  3. Verify that the fuel pressure does not decrease greater than 34 kPa (5 PSI) in 1 minute.
    • If the fuel pressure decreases greater than 34 kPa (5 PSI) 

      Refer to Circuit/System Testing - Fuel Pressure Leaks Down.

    • Go to next step: If the fuel pressure does not decrease greater than 34 kPa (5 PSI) 
    4. WARNING:

    Road test a vehicle under safe conditions and while obeying all traffic laws. Do not attempt any maneuvers that could jeopardize vehicle control. Failure to adhere to these precautions could lead to serious personal injury and vehicle damage.

  4. Operate the vehicle within the conditions of the customer's concern while monitoring the CH-48027  Digital Fuel Pressure Gauge.
  5. Verify the fuel pressure does not drop off during acceleration, cruise or hard cornering.
    • If the fuel pressure drops off 

      Refer to Circuit/System Testing - Fuel Pressure Drops OFF.

    • Go to next step: If the fuel pressure does not drop off 
  6. If the fuel system components test normal, refer to Symptoms - Engine Controls , and Fuel Injector Diagnosis  for further diagnosis.
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