Vibration-Proofing Fuel Pressure Gauges: Effective Strategies And Techniques

A vibrating fuel pressure gauge can be a common problem in certain vehicles, such as the Lance/Saratoga aircraft and the Dodge Ram Van. There are several potential causes and solutions for this issue. One solution is to replace the orifice or add one if it is missing, as this can affect fuel pressure and cause the gauge to vibrate. Another solution is to ensure that the line to the gauge is not completely filled with fuel, as air is needed for dampening. Additionally, a liquid-filled gauge can help to reduce vibration and improve accuracy. Filling the gauge with glycerin or silicone makes it more difficult for the needle to shake, leading to a steadier reading. Dampening movements, such as a silicone dampener near the axis of the pointer, can also help to steady the needle. For extreme cases, a capillary tube and diaphragm seal filled system may be necessary.

Liquid filling with glycerin or silicone

Liquid filling is a common method used to vibration-proof fuel pressure gauges. This process involves filling the cavity of a pressure gauge with a liquid, usually glycerin or silicone, to dampen the internal components and reduce the effects of heavy vibration. This method is particularly useful for applications that involve high dynamic shock and vibration loading.

Glycerine, or glycerin, is a highly viscous liquid that acts as an effective dampening agent. It is suitable for most applications and ambient temperatures. However, glycerin has a limited temperature window. If exposed to temperatures lower than 20°F, it may impact the instrument's performance. At temperatures above 150°F, the glycerin may discolour, making the gauge difficult to read. Therefore, it is important to consider the temperature ratings of the fill fluid to ensure it aligns with the application's temperature range.

Silicone, on the other hand, is significantly less viscous but still offers substantial protection against pulsation and vibration. It has a wider temperature range than glycerin, with a tolerance of 40°F to 200°F. This makes it a suitable choice for applications with extreme temperature requirements.

When filling the case of a pressure gauge with liquid, it is important to leave some space for expansion. The filling liquid will absorb additional water and expand depending on humidity and ambient temperature. Therefore, the case is typically filled to only 80%-90% of its capacity to prevent leakage.

By using liquid filling with glycerin or silicone, the vibrations and pressure peaks are dampened, protecting the mechanical components of the fuel pressure gauge. This method ensures the readability of the gauge by limiting the motion of the pointer, even under severe vibration loads.

Dampening movement with a silicone dampener

Vibration can be an issue for fuel pressure gauges, and one way to mitigate this is by using a silicone dampener. Silicone dampeners are an effective way to reduce the impact of vibrations and resonances on your fuel pressure gauge. They are made of flexible and robust silicone, making them durable and resilient.

Silicone dampeners are typically self-adhesive, making them easy to install. They come in various sizes, such as 20mm, 32mm, and 50mm in diameter, and can bear different loads, so it's important to choose the right size and capacity for your needs. For example, a set of four 50mm dampeners can bear a load of approximately 46kg.

To install a silicone dampener, first, clean the surface of your fuel pressure gauge. Then, simply peel off the protective film from the dampener and stick it to the device. The dampener will act as a soft, vibration-absorbing layer between the gauge and the surface it is mounted on, helping to prevent damage and improve the accuracy of readings.

Silicone dampeners are not just useful for fuel pressure gauges but can also be applied to other devices such as record players, speakers, PCs, and home cinema systems. They help to reduce vibrations, improve sound quality, and protect delicate components from damage.

Capillary tubing with diaphragm seal

Capillary tubing is a useful method to separate a fuel pressure gauge from the direct connection with the process tapping point. This allows the gauge to be installed in a more accessible location. The capillary tubing is filled with liquid, usually glycerine, which can be changed depending on the application. This liquid fills the diaphragm seal remote and the pressure instrument, allowing them to be separated.

The capillary tube also acts as a cooling element, as the distance between the process tapping and the instrument will be greater than a direct installation. This means there is no direct contact between the instrument sensor and the process, which can protect the gauge from damage. The capillary tube also provides a cooling function for process temperature changes.

However, the capillary tube is subject to the process temperature effect, where warming through the process media temperature causes the liquid in the tube to expand or contract, which can lead to errors in pressure readings. This is more likely to occur with shorter capillary lengths. Longer capillary lengths can also affect accuracy due to ambient temperature effects, so it is important to keep the capillary length as short as possible.

Additionally, capillary tubing can introduce a response time lag in the instrument reading. This is influenced by the length and internal diameter of the capillary tube, the viscosity of the fill fluid, and the control volume of the pressure-sensing instrument.

Using a heat gun to drive out water

To vibration-proof a fuel pressure gauge, you can opt for a liquid-filled, shock-proof gauge to handle the vibration from your race car. However, liquid-filled fuel pressure gauges are susceptible to heat, which can cause the gauge to provide inaccurate readings. This is due to the liquid inside the gauge, often glycerin, expanding and causing the internal pressure to rise.

If you are experiencing issues with water in your fuel pressure gauge, you can use a heat gun to drive out the water. Here's a step-by-step guide:

• Locate the source of the water ingress: Check for any leaks or cracks in the fuel lines, hoses, or the gauge itself. Identify where the water is entering the system.
• Disconnect the fuel pressure gauge: Before applying heat, ensure that the fuel pressure gauge is disconnected from any fuel lines or hoses. This will prevent any damage to other components and reduce the risk of injury.
• Set up your work area: Choose a well-ventilated area to work in, as using a heat gun can produce fumes. Place the fuel pressure gauge on a heat-resistant surface, such as a metal workbench or a heat-proof mat. Have some old rags or towels handy to catch any water that may drip out.
• Apply heat with the heat gun: Set the heat gun to a medium setting to avoid damaging the gauge or any nearby components. Start applying heat to the gauge, focusing on the areas where water ingress was identified. The heat will cause the water to evaporate and escape from the gauge.
• Use a damp cloth to wipe down the gauge: Once you've applied heat to the gauge, use a damp cloth to wipe away any residue or remaining water. This will help to ensure that all water has been removed and prevent any mineral deposits from forming.
• Reassemble and test the gauge: After the gauge has cooled down, carefully reconnect it to the fuel lines or hoses. Start the engine and observe the gauge to ensure it is functioning correctly and providing accurate readings.

It is important to note that using a heat gun can be dangerous, so always exercise caution and wear appropriate protective gear, including safety goggles and heat-resistant gloves. Additionally, be mindful of any nearby components that may be sensitive to heat and take steps to protect them from the heat gun.

By following these steps, you can effectively use a heat gun to drive out water from your fuel pressure gauge and ensure its accurate and reliable performance.

Drain and reconnect the fuel line

To drain and reconnect the fuel line, you will need to relieve the pressure in the fuel line. You can do this by pulling the fuel pump fuse and starting the car, which will use all the fuel in the lines. You can also try turning the engine over to relieve any pressure.

If you are unable to find the fuse, you can disconnect the fuel pump connector at the tank. Jack up the car to locate the connector, which should be at the rear of the tank. Disconnecting the connector is the same as pulling the fuse.

Once the pressure has been relieved, carefully and slowly undo the fuel lines. Place a pan underneath the drainage plug and unscrew it using a spanner or socket wrench. The fuel will start to drain out, so make sure you have enough pans to catch the drained fuel and avoid any spills.

After draining the fuel, replace the drain plug tightly and refill the car with fuel. Be careful to properly reconnect the fuel lines and the drain plug.

Frequently asked questions