P0451 Fault on 2000 Suzuki Esteem Sedan - Fuel Pumping Issue Due to EVAP System Pressure
2000 Suzuki Esteem Sedan (L4, 1.8L engine) I'm assisting my nephew who is experiencing a persistent issue with his vehicle's fuel filling system. When attempting to refill the tank at a gas station, the fuel pump stops after only a small amount of fuel is added — it must be filled slowly in a trickle manner. This behavior suggests an obstruction or excessive pressure within the fuel fill tube or EVAP (Evaporative Emission Control) system. I recently removed and inspected the fuel tank assembly, including all components of the EVAP system. The issue appears to stem from abnormally high tank pressure: the check valve or flap located between the filler hose and the fuel tank is being forced shut by this pressure. This plastic-valve component shows no visible damage or blockage, and the fill tube itself is clear. All key components have been checked and replaced: - The Fuel Tank Pressure Sensor has been replaced - The EVAP canister is clean and dry - The EVAP air suction filter was previously full of water but is now dry and intact after removal The only component not replaced is the Vapor Control Valve (VCM). Despite these repairs, the OBD2 diagnostic code P0451 persists, and the fuel filling issue remains unresolved. Could this be a faulty or improperly seated vapor control valve? Is there any known compatibility or installation issue with the 2000 Suzuki Esteem's EVAP system? Thanks for your help — located in Milwaukee, WI.
Is the Vapor Control Valve (VCM) mounted at the top of the fuel tank? Has it been inspected or tested for proper operation? Are there any kinks or restrictions in the vacuum lines leading to or from the valve? Did this issue develop after replacing the Fuel Tank Pressure Sensor? If so, could that replacement have triggered a system misalignment? What happens if you disconnect the vacuum line downstream of the tank — does fuel flow normally when the line is removed and the tank is reinstalled? This test might help determine whether the pressure buildup originates in the EVAP system or elsewhere.