Kia Optima Hybrid: Evaporative Emission Control System / NVLD(Natural Vacuum Leakage Detection) Description and Operation

Kia Optima Hybrid (TF HEV) 2016-2020 Service Manual / Emission Control System / Evaporative Emission Control System / NVLD(Natural Vacuum Leakage Detection) Description and Operation

Description

NVLD(Natural Vacuum Leakage Detection) is located between the canister and the fuel tank air filter. NVLD is to detect leaks equivalent to a 0.5 mm hole in the fuel tank, canister and hoses. When the engine has been running, the temperature of the fuel in the fuel tank is raised slightly. When the engine is shut off, the temperature of the fuel should drop. The ideal gas law states that in a sealed system the pressure drops proportionately to a drop in temperature.

[No leak]

[With 0.5mm leak]

While the engine is shut off, ECM monitors a pressure switch that is built into the NVLD for detecting slight drop in pressure. If the switch change is not detected after an engine shut down, it assumes there is a leak in the sealed system.

Fuel Tank Air Filter Repair procedures

Removal 1. Turn the ignition switch OFF and disconnect the battery negative (-) cable. 2. Lift the vehicle. 3. Disconnect the canister close valve connector (A). 4. Disconnect the ventilation hose (B) ...

NVLD(Natural Vacuum Leakage Detection) Specifications

Specification Pressure [kPa (kgf/cm?, in H2O)Output Voltage (V)-6.67 (-0.068, -26.8)0.502.5+6.67 (0.068, 26.8)4.5 ...

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