Fuel pump safety switches are essential components in modern vehicles, designed to shut off the fuel pump in the event of a crash or collision, preventing fuel leaks and potential fires. These switches play a crucial role in enhancing vehicle safety and protecting both the driver and passengers. In this comprehensive guide, we will delve into the different types of fuel pump safety switches, their technical specifications, and their typical operation within a vehicle.
Types of Fuel Pump Safety Switches
1. Inertia Safety Switch
- Description: The inertia safety switch is the most common type of fuel pump safety switch, typically installed in the +12 volt feed wire to an electric fuel pump.
- Functionality: This switch is designed to shut off the fuel pump in the event of a crash or hard shock. When the vehicle experiences a significant impact, the switch contacts open, shutting down the fuel pump and potentially triggering a warning light or GPS distress locator.
- Technical Specifications:
- Operating Criteria: The inertia safety switch operates based on acceleration and deceleration over time. It is designed to trip in the event of a high-speed or low-speed crash, but not for minor impacts such as hitting a curb.
- Contact Rating: The inertia safety switch has a 10 Amp contact rating.
- Reset Mechanism: The switch can be reset by pressing the rubber diaphragm.
- Terminal Configuration: The switch typically has three terminals: a common terminal, a normally open terminal, and a normally closed terminal.
2. Low Oil Pressure Ignition or Electric Fuel Pump Shutoff Switch
- Description: This switch is designed to shut off the ignition or electric fuel pump when the oil pressure drops below a certain threshold, typically around 12 PSI.
- Functionality: The switch is typically connected to a 1/8″ NPT switch, which monitors the oil pressure and triggers the fuel pump shutdown when the pressure falls below the predetermined level.
3. Universal Safety Switch
- Description: The universal safety switch is designed to work with various applications and has both normally open and normally closed terminals.
- Functionality: This switch can be used for different types of fuel pumps and is often employed in boat motor applications, providing a versatile solution for fuel pump safety.
Technical Specifications and Functionality
Operating Criteria
The inertia safety switch operates based on acceleration and deceleration over time. It is designed to trip in the event of a high-speed or low-speed crash, but not for minor impacts such as hitting a curb. The switch is calibrated to detect sudden changes in velocity, which are indicative of a significant collision.
Contact Rating
The inertia safety switch has a 10 Amp contact rating, meaning it can safely interrupt and control the flow of up to 10 Amps of electrical current. This rating ensures that the switch can handle the power requirements of the electric fuel pump without risk of overloading or failure.
Reset Mechanism
The inertia safety switch can be reset by pressing the rubber diaphragm. This action restores the connection between the common terminal and the normally closed terminal, allowing the fuel pump to be reactivated after the switch has been triggered.
Terminal Configuration
The inertia safety switch typically has three terminals:
– Common terminal
– Normally open terminal
– Normally closed terminal
This configuration allows the switch to interrupt the power supply to the fuel pump when the contacts flip during a crash, while also providing a means to reset the switch and restore the original connection.
Typical Operation in a Vehicle
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Installation: The inertia safety switch is installed in the +12 volt feed wire to the electric fuel pump, ensuring that it can effectively shut off the power supply in the event of a collision.
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Armed State: When the switch is armed and the rubber diaphragm is pressed, there is contact between the common terminal and the normally closed terminal, allowing the fuel pump to operate normally.
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Crash Detection: In the event of a crash, the switch contacts flip, breaking the connection between the common terminal and the normally closed terminal, and connecting the common terminal to the normally open terminal.
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Fuel Pump Shutdown: This action breaks the power supply to the fuel pump, shutting it off to prevent fuel leaks and potential fires.
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Reset: The switch can be reset by pressing the rubber diaphragm, restoring the original connection between the common terminal and the normally closed terminal, allowing the fuel pump to be reactivated.
References
- Longacre 43600 Fuel Shut-Off Switch: https://www.amazon.com/Longacre-43600-Fuel-Shut-Off-Switch/dp/B001NNBINQ
- Fuel Pump Safety Switch Demonstration: https://www.youtube.com/watch?v=_2zvMPCcEaM
- Mr. Gasket 7872 Safety Switch: https://www.amazon.com/Mr-Gasket-7872-Safety-Switch/dp/B00068OQ3S
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