Fuel Level Indicator Diagnostic via Vacuum Decay
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Solution Overview
Problem
Existing fuel level indicators in fuel tanks struggle to determine if they are functioning correctly, especially when the fuel level is within the ullage or empty region, as there is no change in measured fuel level, making it difficult to verify their functionality.
Innovation Solution
A diagnostic system that uses a controller to pull a vacuum on the fuel tank from an initial pressure to a reference pressure, measuring the rate of pressure change and comparing it to the fuel level indicated by the fuel level indicator, providing a diagnostic code based on the correlation between the two.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fuel level indicators are used to monitor fuel level, then fuel level information can be provided to the user, but the functionality of the fuel level indicator cannot be verified when the fuel level is within the ullage or empty region
Solution Approach 1:
The system performs a vacuum decay test before the fuel level indicator needs to be verified during normal operation. By pre-establishing the relationship between pressure decay rate and fuel level through controlled testing, the system creates a reference framework that enables later verification of FLI functionality without requiring fuel level changes. This preliminary calibration allows the system to detect FLI malfunctions even when the fuel level remains constant in the ullage or empty region.
Solution Approach 2:
The system introduces pressure as an intermediary parameter to verify fuel level indicator functionality. Instead of directly measuring fuel level changes to verify FLI operation, the system uses pressure decay rate as an intermediate measurement that correlates to fuel level. This intermediary approach allows verification of FLI functionality through comparison between the FLI reading and the pressure-derived fuel level estimate, even when the actual fuel level is constant.
2Reliability
If the fuel level is within the ullage or empty region, then the fuel tank has sufficient space, but there is no change in measured fuel level making it impossible to determine if the FLI is functioning properly
Solution Approach 1:
The system replaces the mechanical measurement approach with a pneumatic one. Instead of relying on the mechanical movement of the fuel level indicator to detect fuel level changes, the system uses pressure measurement and vacuum decay testing to infer fuel level. This substitution allows the system to obtain fuel level information through pressure changes rather than direct mechanical measurement, enabling functionality verification even when the mechanical FLI shows no movement.
Solution Approach 2:
The system changes the measurement parameter from direct fuel level measurement to pressure decay rate measurement. By applying a vacuum and measuring the rate at which pressure equalizes, the system obtains an indirect measurement of fuel level that is independent of the FLI's mechanical position. This parameter change enables the system to detect FLI functionality by comparing the FLI reading against the pressure-derived fuel level estimate.
3Reliability
If a diagnostic system is implemented to verify fuel level indicators, then functionality can be determined, but the system complexity increases with additional sensors and control logic
Solution Approach 1:
The vacuum pump and pressure sensor are designed to serve multiple functions within the fuel system. The vacuum pump is used both for vapor recovery operations and for conducting vacuum decay tests to verify FLI functionality. The pressure sensor serves both to monitor fuel tank pressure during normal operation and to measure pressure decay rate for diagnostic purposes. This multi-functionality allows the diagnostic capability to be added without requiring dedicated diagnostic-only components, thereby limiting the increase in system complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method allows for the determination of whether the fuel level indicators are functional at any fuel fill level, including when the level is within the ullage or empty region, ensuring proper operation by correlating pressure changes with fuel levels, thus enabling effective diagnostic testing.
Implementation Method 1
pull a vacuum on the fuel tank from an initial pressure to a reference pressure while operating a timer to determine a rate of pressure change in the fuel tank
Data Source
AI summary
A vehicle is provided with a controller and a fuel system having a fuel tank, a fuel level indicator (FLI), and a pressure sensor. The controller is configured to: pull a vacuum on the tank from an initial pressure to a reference pressure, and provide a diagnostic code in response to comparing a fuel level indicated by the FLI to a rate of pressure change in the tank. A method for performing a fuel level indicator (FLI) diagnostic for a vehicle is provided. A vacuum is pulled on the fuel tank from an initial pressure to a reference pressure. A diagnostic code is provided in response to comparing a fuel level indicated by an FLI to a rate of pressure change.