Method of leak detection during low engine vacuum for an evaporative emission control system
First Claim
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1. A method of leak detection for an evaporative emission control system during periods of low engine vacuum, said method comprising the steps of:
- closing a canister vent valvepulsing a leak detection pump at a predetermined rate to pressurize the evaporative emission control system;
determining whether an engine vacuum level is less than a predetermined vacuum level;
maintaining pressurization of the evaporative emission control system by pulsing the leak detection pump if the engine vacuum level is less than the predetermined vacuum level;
incrementing a current low vacuum mode indicator and an accumulated low vacuum indicator;
determining if the accumulated low vacuum indicator is less than a predetermined accumulated low vacuum indicator limit;
ending said method if the accumulated low vacuum indicator is equal to or greater than the predetermined accumulated low vacuum indicator limit;
determining if a vacuum of a vacuum pump is less than a predetermined minimum vacuum limit if the accumulated low vacuum indicator is less than the predetermined accumulated low vacuum indicator limit;
pulsing the leak detection pump at a predetermined frequency if the accumulated low vacuum indicator is less than the predetermined accumulated low vacuum indicator limit; and
ending said method if the accumulated low vacuum indicator time is greater than the predetermined accumulated low vacuum indicator limit.
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Abstract
A method of leak detection for an evaporative emission control system during periods of low engine vacuum includes the steps of pulsing a leak detection pump at a predetermined rate and determining whether engine vacuum level is low. The method also includes the steps of maintaining pressurization of the evaporative emission control system if the engine vacuum level is low, maintaining pressurization behind a vapor canister vent valve if the engine vacuum level is low, and detecting for leaks in the evaporative emission control system after a normal engine vacuum level is attained.
32 Citations
4 Claims
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1. A method of leak detection for an evaporative emission control system during periods of low engine vacuum, said method comprising the steps of:
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closing a canister vent valve pulsing a leak detection pump at a predetermined rate to pressurize the evaporative emission control system; determining whether an engine vacuum level is less than a predetermined vacuum level; maintaining pressurization of the evaporative emission control system by pulsing the leak detection pump if the engine vacuum level is less than the predetermined vacuum level; incrementing a current low vacuum mode indicator and an accumulated low vacuum indicator; determining if the accumulated low vacuum indicator is less than a predetermined accumulated low vacuum indicator limit; ending said method if the accumulated low vacuum indicator is equal to or greater than the predetermined accumulated low vacuum indicator limit; determining if a vacuum of a vacuum pump is less than a predetermined minimum vacuum limit if the accumulated low vacuum indicator is less than the predetermined accumulated low vacuum indicator limit; pulsing the leak detection pump at a predetermined frequency if the accumulated low vacuum indicator is less than the predetermined accumulated low vacuum indicator limit; and ending said method if the accumulated low vacuum indicator time is greater than the predetermined accumulated low vacuum indicator limit.
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2. A method of leak detection for an evaporative emission control system to maintain system pressurization and a canister vent valve seal during times of low engine vacuum, said method comprising the steps of:
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pulsing a leak detection pump at a predetermined rate; incrementing a current low vacuum mode indicator and an accumulated low vacuum indicator; determining if the accumulated low vacuum indicator is less than a predetermined accumulated low vacuum indicator limit; ending said method if the accumulated low vacuum indicator is equal to or greater than the predetermined accumulated low vacuum indicator limit; determining if a vacuum of a vacuum pump is less than a predetermined minimum vacuum limit if the accumulated low vacuum indicator is less than the predetermined accumulated low vacuum indicator limit; pulsing a leak detection pump at a predetermined frequency if the accumulated low vacuum indicator is less than the predetermined accumulated low vacuum indicator limit; and ending said method if the accumulated low vacuum indicator timer is greater than the predetermined accumulated low vacuum indicator limit. - View Dependent Claims (3, 4)
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Specification