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Home >> GMC >> 2001 >> C3500 HD 6.5 F, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - 6.5L - Troubleshooting >> Fuel System Diagnosis >> Fuel Lift Pump Suction Line Check

Fuel Lift Pump Suction Line Check

  1. Remove the fuel tank cap and repeat the Lift Pump Flow Check.
    • If the flow is more than 0.24 liter (1/2 pint) in 15 seconds, replace the defective fuel tank cap.
    • If the flow is less than 0.24 liter (1/2 pint) in 15 seconds, proceed to the next step.
  2. Separate the lift pump suction line from the fuel sender.
  3. Connect the suction line to a source of clean fuel by using an additional hose.
  4. Repeat the Lift Pump Flow Check.
    • If the flow is more than 0.24 liter (1/2 pint) in 15 seconds, proceed to Fuel System Air Leak Check.
    • If the flow is less than 0.24 liter (1/2 pint) in 15 seconds, proceed to Step 5.
  5. Check the lift pump suction line for a restriction.
    • If a restriction exists, repair the restriction and recheck lift pump flow.
    • If no restriction exists, replace the lift pump and recheck the lift pump flow. Refer to Fuel Pump Electrical Circuit Diagnosis .
  6. Attach the lift pump suction line to the fuel sender.
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