Patent ID: 9739248
Date: 2017-08-22
CPC Classifications: F02M

Claim:
1. A method for a vehicle with an engine, comprising: with a temperature sensor, measuring ambient temperature; generating engine off pressure in a fuel system for leak diagnostics, the pressure held via first and second mechanical relief valves and without a valve holding current, the relief valves positioned in parallel in a vent line, outside of a fuel tank, between a fuel vapor canister and a vent to the atmosphere, the canister also positioned outside of the fuel tank; in response to the measured ambient temperature increasing at a rate greater than a threshold temperature increase rate during the generation of the engine off pressure, initiating leak testing, indicating a leak in the fuel system in response to a pressure increase in the fuel system less than a threshold, and indicating no leak in the fuel system in response to a pressure increase in the fuel system greater than the threshold; and generating engine off vacuum in the fuel system, the vacuum held via the first and second mechanical relief valves and without a valve holding current; in response to the measured ambient temperature decreasing at a rate greater than a threshold temperature decrease rate during the generation of the engine off vacuum, initiating leak testing, indicating a leak in the fuel system in response to a vacuum increase in the fuel system less than a threshold, and indicating no leak in the fuel system in response to a vacuum increase in the fuel system greater than the threshold.