Alleman Hall McCoy Russell & Tuttle LLP
Feedforward compensation for fuel system vacuum relief
Methods and systems are provided for relieving excess fuel tank vacuum in a vehicle. In one example, responsive to a fuel tank vacuum above a threshold or a rise in fuel tank vacuum level being higher than a threshold rate, a canister purge valve is opened to dissipate the fuel tank vacuum into an engine intake manifold while the engine is combusting, and the amount of intake air inducted into the intake manifold is adjusted such that air/fuel ratio errors are reduced. In this way, fuel tank vacuum may be relieved under engine operating conditions wherein the likelihood of air/fuel ratio errors are high, thus enabling rapid relief of fuel tank vacuum such that fuel tank degradation can be reduced and fuel system integrity can be better maintained.
Ford Global Technologies, LLC
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Yonghua
Li