Fuel system control

摘要

Methods are provided for reliving excess vacuum from a fuel tank. In response to elevated fuel tank vacuum levels, a canister purge valve is opened to dissipate the vacuum to an engine intake manifold while the engine is not combusting. Alternatively, the purge valve is opened to dissipate the excess vacuum to the intake manifold while the engine is combusting during conditions when the likelihood of air-fuel ratio errors are lower or when any incurred errors are better tolerated.

主权项

1. A method for a fuel system coupled to an engine, comprising:
in response to a rise in fuel tank vacuum above a threshold,
opening a canister purge valve to dissipate excess fuel tank vacuum into an engine intake manifold, a timing of the opening based on intake manifold vacuum, wherein the timing of opening based on intake manifold vacuum includes opening the canister purge valve after the intake manifold vacuum is lower than the fuel tank vacuum.