Method for detecting fuel system degradation

• US 10,077,731 B2
• Filed: 05/22/2015
• Issued: 09/18/2018
• Est. Priority Date: 05/22/2015
• Status: Active Grant

• Current Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Original Assignee: Ford Global Technologies, LLC (Ford Motor Company)
• Inventors: Dudar, Aed M., Pearce, Russell Randall, Yang, Dennis Seung-Man
• Primary Examiner(s): Cronin, Stephen K
• Assistant Examiner(s): Bacon, Anthony L
• Application Number:
  US14/720,464
• Publication Number:
  US 20160341141A1
• Time in Patent Office: 1,215 Days
• CPC Class Codes: B60K 15/03504 adapted to avoid loss of fuel or fuel vapour, e.g. with vapour recovery systems
• CPC Class Codes: B60K 15/03519 Valve arrangements in the vent line
• CPC Class Codes: B60K 2015/03118 Multiple tanks, i.e. two or more separate tanks
• CPC Class Codes: B60K 2015/03514 with vapor recovery means
• CPC Class Codes: F02D 2041/225 Leakage detection
• CPC Class Codes: F02D 33/003 Controlling the feeding of liquid fuel from storage containers to carburettors or fuel-injection apparatus control of electrical fuel pumps F02D41/3082, controlling fuel flow to a common rail F02D41/3845; Failure or leakage prevention; Diagnosis or detection of failure; Arrangement of sensors in the fuel system; Electric wiring; Electrostatic discharge
• CPC Class Codes: F02D 41/22 Safety or indicating devices for abnormal conditions in air/fuel ratio feedback systems F02D41/1495, in electric control linkage F02D11/107, in purge control systems F02M25/0809
• CPC Class Codes: F02M 25/0809 Judging failure of purge control system
• CPC Class Codes: F02M 25/089 Layout of the fuel vapour installation
• CPC Class Codes: F02M 37/0088 Multiple separate fuel tanks or tanks being at least partially partitioned
• CPC Class Codes: G01M 3/3209 Details, e.g. container closure devices
• CPC Class Codes: G01M 3/3245 using a level monitoring device G01M3/3272 takes precedence
• CPC Class Codes: G01M 3/3272 for verifying the internal pressure of closed containers
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

Methods and systems are provided for detecting leaks in an engine fuel system coupled in a vehicle including a first fuel tank and a second fuel tank, and a canister coupled together via a three-way valve. A leak test may be initially performed on the first fuel tank by supplying vacuum to the first fuel tank. The second fuel tank may be tested for leaks immediately following the leak test on the first fuel tank by recycling vacuum from the first fuel tank.

Claims

1. A method for performing leak testing in a fuel system of a vehicle engine, comprising:

applying vacuum to a first fuel tank having a lower fuel fill level than a second fuel tank, including;

applying vacuum to the first fuel tank via a vacuum pump, then ceasing the application of vacuum, monitoring pressure changes in the fuel system based on output from a pressure sensor arranged in the fuel system, and determining whether there is a leak in the first fuel tank based on the monitored pressure changes; and

then

transferring the vacuum from the first fuel tank to the second fuel tank, then ceasing the transfer of vacuum, monitoring pressure changes in the fuel system based on output from the pressure sensor, and determining whether there is a leak in the second fuel tank based on the monitored pressure changes.

2. The method of claim 1, further comprising measuring and comparing fuel fill levels of the first and second fuel tanks.

3. The method of claim 2, further comprising, when the fuel fill level of the second fuel tank is lower than the fuel fill level of the first fuel tank:

applying the vacuum at first to the second fuel tank via the vacuum pump, then ceasing the application of vacuum, monitoring pressure changes in the fuel system based on output from the pressure sensor, and determining whether there is a leak in the second fuel tank based on the monitored pressure changes; and

then

transferring the vacuum from the second fuel tank to the first fuel tank, then ceasing the transfer of vacuum, monitoring pressure changes in the fuel system based on output from the pressure sensor, and determining whether there is a leak in the first fuel tank based on the monitored pressure changes.

4. The method of claim 3, further comprising, when the first fuel tank and the second fuel tank have substantially equal fuel fill levels:

estimating fuel temperature and a level of fuel slosh in each of the first and second fuel tanks;

selecting one of the first fuel tank and the second fuel tank based on one or more of the estimated fuel temperatures and levels of fuel slosh, applying vacuum at first to the one selected fuel tank via the vacuum pump, then ceasing the application of vacuum, monitoring pressure changes in the fuel system based on output from the pressure sensor, and determining whether there is a leak in the one selected fuel tank based on the monitored pressure changes; and

then

transferring the vacuum from the one selected fuel tank to a remaining fuel tank, then ceasing the transfer of vacuum, monitoring pressure changes in the fuel system based on output from the pressure sensor, and determining whether there is a leak in the remaining fuel tank based on the monitored pressure changes.

5. The method of claim 1, further comprising identifying leaks in a fuel system canister prior to applying the vacuum to the first fuel tank, and wherein each of the first fuel tank and the second fuel tank is isolated from the fuel system canister while identifying leaks in the fuel system canister by adjusting a valve to a first position, the valve coupled to each of the fuel system canister, the first fuel tank, and the second fuel tank.

6. The method of claim 5, wherein the applying of vacuum to the first fuel tank includes adjusting the valve to a second position in which the first fuel tank and the fuel system canister are in fluidic communication.

7. The method of claim 6, wherein transferring vacuum from the first fuel tank to the second fuel tank includes adjusting the valve to a third position in which the first fuel tank, the second fuel tank, and the fuel system canister are in fluidic communication.

8. The method of claim 5, wherein the pressure sensor is used to identify leaks in the fuel system canister, leaks in the first fuel tank, and leaks in the second fuel tank.

9. The method of claim 8, further comprising indicating a leak in the first fuel tank in response to a pressure in the first fuel tank being higher than a first threshold pressure.

10. The method of claim 9, further comprising indicating a leak in the second fuel tank in response to a pressure in the second fuel tank being higher than a second threshold pressure, the second threshold pressure being different from the first threshold pressure.

11. The method of claim 10, wherein the second threshold pressure is based on the vacuum transferred from the first fuel tank to the second fuel tank.

12. The method of claim 1, further comprising:

when the vehicle engine is on,

applying vacuum to the first fuel tank via one of intake manifold vacuum and the vacuum pump, then ceasing the application of vacuum, monitoring pressure changes in the fuel system based on output from the pressure sensor, and determining whether there is a leak in the first fuel tank based on the monitored pressure changes; and

then

transferring the vacuum from the first fuel tank to the second fuel tank, then ceasing the transfer of vacuum, monitoring pressure changes in the fuel system based on output from the pressure sensor, and determining whether there is a leak in the second fuel tank based on the monitored pressure changes.

13. The method of claim 1, wherein the vehicle engine is fueled via the second fuel tank while identifying leaks in the first fuel tank, and wherein the vehicle engine is fueled via the first fuel tank while identifying leaks in the second fuel tank.

14. A method for a fuel system in an engine, comprising:

adjusting a three-way valve to fluidically couple a first fuel tank to a vacuum source via a fuel system canister, then applying vacuum from the vacuum source to the first fuel tank, then ceasing the application of vacuum, monitoring pressure changes in the fuel system based on output from a pressure sensor arranged in the fuel system, and determining whether there is a leak in the first fuel tank based on the monitored pressure changes; and

then

modifying the three-way valve to fluidically couple the first fuel tank to a second fuel tank, then transferring the vacuum from the first fuel tank to the second fuel tank, then ceasing the transfer of vacuum, monitoring pressure changes in the fuel system based on output from the pressure sensor, and determining whether there is a leak in the second fuel tank based on the monitored pressure changes.

15. The method of claim 14, wherein the three-way valve blocks fluidic communication between the first fuel tank and the second fuel tank while diagnosing the first fuel tank for leaks, and wherein diagnosing the second fuel tank for leaks is performed sequentially after diagnosing the first fuel tank for leaks to distinguish degradation between the first fuel tank and the second fuel tank.

16. The method of claim 14, further comprising diagnosing the fuel system canister for leaks prior to diagnosing the first fuel tank for leaks, and wherein diagnosing the fuel system canister for leaks includes adjusting the three-way valve to decouple the fuel system canister from each of the first fuel tank and the second fuel tank.

17. A method for diagnosing leaks in a fuel system of an engine, comprising:

estimating fuel fill levels in at least two fuel tanks; and

sequentially performing leak tests for two or more of the at least two fuel tanks in order of their fuel fill levels, from lowest to highest.

18. The method of claim 17, wherein the fuel fill levels are estimated using fuel level sensors positioned in each of the at least two fuel tanks.

19. The method of claim 17, wherein performing a leak test for a fuel tank of the at least two fuel tanks comprises:

applying vacuum to the fuel tank undergoing the leak test; and

then

ceasing application of the vacuum, monitoring changes in pressure in the fuel system with a pressure sensor arranged in the fuel system, and determining whether there is a leak in the fuel tank based on the monitored pressure changes.