Pressure Testing A Boat Fuel Tank: Finding Leaks

If you're a boat owner, you'll know that the dreaded fuel smell is something you're likely to come across at some point. If you've checked everything and are almost certain that the fuel tank is the culprit, it's time to pressure test it. But how do you do that? This article will give you a step-by-step guide on how to pressure test a boat fuel tank for leaks, so you can get back to enjoying your time on the water.

How to identify a fuel leak in a boat

If you spend enough time boating, you will eventually come across a fuel smell. After checking everything, you may conclude that the fuel tank is bad. Here is a simple way to pressure test a boat fuel tank at home without expensive tools.

Steps to Identify a Fuel Leak in a Boat:

Acquire the Necessary Tools:

• Hose pinch pliers
• An inflatable pipe plug
• A low-pressure air pressure gauge that can be tee'd into a 3/8" fuel hose with a Schrader valve

Gain Access to the Fuel Tank Components:

Most boats have access ports for the two main portions of the fuel tank: the fill and vent part (toward the front of the tank) and the pickup tubes and sender section (at the back or aft of the tank). However, some older boats may not have access to these sections.

Install the Inflatable Pipe Plug to Shut Off the Fill Port:

Insert the inflatable pipe plug into the fuel fill hole and pump it up to shut off the fuel fill hose. Ensure that the plug is seated properly to prevent air leaks.

Pinch Off the Fuel Tank Vent Hose:

Use the hose pinch pliers to pinch off the vent hose, ensuring that it is completely compressed to prevent air escape.

Remove the Fuel Hose from the Pickup Tube Fitting:

Slice a small section of the fuel hose connected to the pickup tube to easily remove it. Then, install the low-pressure air pressure gauge and hose.

Pump Air into the Tank:

It is crucial not to exceed 3 psi of pressure, as too much air can damage the tank. Slowly work your way up to 2 psi and observe the pressure gauge.

Locate the Leak:

If the pressure gauge drops, there may be a leak. Spray soapy water around the pickups and fuel sender, as leaks often occur in these areas. Look for air bubbles, and ensure that all ports and hoses are properly plugged. Continue pumping the tank to 2 psi and spraying soapy water until you are certain the leak is not coming from the top of the tank. Also, keep an eye on the bilge to ensure that fuel is not leaking into it, which would indicate a failed fuel tank that needs replacement.

Tools required to pressure test a boat fuel tank

To pressure test a boat fuel tank, you will need the following tools:

• Hose pinch pliers: These pliers are designed to close onto a hose and stay shut until released, allowing you to pinch off hoses and prevent air from escaping.
• Inflatable pipe plug: This plumbing tool fits into a pipe, and when pressure is applied, it expands to close off the pipe.
• Low-pressure air pressure gauge: This gauge can be tee'd into a 3/8" fuel hose with a Schrader valve, allowing you to monitor the air pressure in the tank.
• Short piece of 3/8" fuel hose: This hose will be used to connect the air pump or tank of compressed air to the Schrader valve on the pressure gauge.
• Brass fitting: One side of the brass fitting has a 3/8" hose barb, and the other side has a threaded adapter, allowing you to connect the fuel hose to the pressure gauge assembly.
• Adapter: This adapter connects the threaded side of the brass fitting to the Schrader valve.
• Air pump or tank of compressed air: This provides the air pressure needed to test the tank.
• Utility knife: A utility knife with a new blade is useful for slicing through the fuel hose connected to the pickup tube, making it easier to remove.
• Large screwdriver: Used to work the fuel hose off the pickup tube.
• Hose clamp: This is used to secure the pressure testing tool onto the hose barb.

With these tools, you can perform a pressure test on your boat's fuel tank to check for leaks. Remember to exercise caution when working with fuel systems and follow appropriate safety procedures.

The process of pressure testing a boat fuel tank

Pressure testing a boat fuel tank is a crucial procedure to ensure the safety and proper functioning of your boat. Here is a detailed guide on how to perform this task effectively:

Step 1: Gather the Required Tools and Materials

• Hose pinch pliers
• Inflatable pipe plug
• Low-pressure air pressure gauge that can be tee-ed into a 3/8" fuel hose with a Schrader valve
• Air pump or a tank of compressed air

Step 2: Access the Fuel Tank Components

Locate the fuel fill hose, vent hose access ports, and the fuel pickup access. Most boats have access ports for the fill and vent parts towards the front of the tank, while the pickup tubes and sender section are at the back.

Step 3: Install the Inflatable Pipe Plug

Insert the inflatable pipe plug into the fuel fill port and pump it up to shut off the fuel fill hose. Ensure that the plug is seated properly to prevent air leaks.

Step 4: Pinch Off the Fuel Tank Vent Hose

Use the hose pinch pliers to close off the vent hose. Squeeze the pliers tightly to completely compress the hose and prevent air escape. Be careful not to damage old hoses, as they may split.

Step 5: Remove the Fuel Hose from the Pickup Tube

Slice a small section of the fuel hose connected to the pickup tube to easily remove it. This will save you time and frustration, as the fuel hose can become stuck over time.

Step 6: Install the Low-Pressure Air Pressure Gauge

Connect the low-pressure air pressure gauge and hose to the pickup tube fitting. Ensure that all connections are secure and airtight.

Step 7: Pump Air into the Tank

Start pumping air into the tank, but do not exceed 3 lbs of pressure (3 psi). Understand that too much air can damage the tank. Slowly work your way up to 2 psi and observe the pressure gauge.

Step 8: Locate Leaks

If the pressure gauge drops, it indicates a leak. Spray soapy water around the pickups, fuel sender, and fittings. Look for air bubbles, which indicate the presence of a leak. If no leaks are found, ensure that all ports and hoses are properly closed off.

Step 9: Monitor the Bilge

Keep an eye on the bilge to ensure that fuel is not leaking into it. If fuel is present in the bilge, the boat's fuel tank has failed, and replacement is necessary.

Safety precautions when pressure testing a boat fuel tank

Before you begin pressure testing your boat fuel tank, there are several safety precautions you should take to ensure the process is safe and effective. Here are some detailed instructions to guide you through the process safely:

Prepare the Necessary Tools

Firstly, ensure you have all the required tools, including hose pinch pliers, an inflatable pipe plug, and a low-pressure air pressure gauge that can be tee'd into a 3/8" fuel hose with a Schrader valve. These tools will help you control the air pressure and identify any leaks.

Locate the Fuel Tank Components

Access the fuel tank components, including the fuel fill hose, vent hose access ports, and fuel pickup access. Understand the layout of your boat's fuel system and be cautious when handling any fuel-related equipment.

Close Off Access Points

Use the inflatable pipe plug to shut off the fuel fill port. Ensure it's securely in place and free of any obstructions. Then, use the hose pinch pliers to pinch off the fuel tank vent hose, preventing air from escaping. This step is crucial to creating a closed system for accurate pressure testing.

Remove the Fuel Hose and Install the Pressure Gauge

Remove the fuel hose from the pickup tube fitting. Be cautious when handling the fuel hose, as it may be stuck due to the effects of gasoline. Install the low-pressure air pressure gauge and hose onto the pickup tube fitting. Ensure a secure connection to prevent leaks during testing.

Understand Safe Air Pressure Levels

Before pumping air into the tank, it's crucial to understand safe air pressure levels. Do not exceed 3 lbs of pressure (3 psi) to avoid damaging the tank. Stay within the range of 2-3 psi to safely identify any leaks without risking damage to the tank.

Monitor for Leaks

Once you've reached the desired air pressure, monitor the pressure gauge. If the pressure drops, it indicates a potential leak. Spray soapy water on the fittings, sender, and ports to check for air bubbles, which would confirm the presence of a leak. If no leaks are found, release the pressure and ensure all tools are properly connected and sealed before retesting.

Be Mindful of Your Surroundings

Throughout the pressure testing process, be mindful of your surroundings and take necessary precautions to avoid any accidents. Keep flammable materials away from the work area, and ensure proper ventilation to prevent the buildup of fuel vapors. Always prioritize your safety and the safety of those around you.

By following these safety precautions, you can effectively pressure test your boat fuel tank while minimizing the risk of damage or injury. Remember to work carefully, stay within safe air pressure limits, and monitor for any signs of leaks or abnormalities.

Alternative methods to pressure testing

Submerging the Tank

One method is to submerge the tank in a swimming pool and watch for air bubbles. This will require sealing all pipe fittings and sender holes. However, some people have pointed out the potential issues with this method, including the difficulty of sinking a large tank and the risk of getting fuel or oil in the pool.

Using a Compressor

If you have access to a compressor, you can create a setup with an inline pressure regulator, pressure gauge, and fittings adapted to the fuel line fitting. This will allow you to pressurize the tank and check for leaks without having to submerge it.

Using a Foot Pump and Pressure Gauge

A foot pump and pressure gauge can be used to create positive pressure in the tank, and then you can look for bubbles. It is recommended to aim for 3-5 psi, as this is the standard pressure used by tank manufacturers for testing.

Using a Tire Pump

Similar to the compressor method, you can use a tire pump to pressurize the tank and then use a test gauge adapted to your fittings to check for leaks.

Using Oil

You can squirt a light, clean motor oil on the seams and around fittings. Any leaks will show almost immediately as the oil will seep out from the opposite side, even if air and water may not.

Using a Radiator Repair Shop

Taking your fuel tank to a local radiator repair shop is another option, as they often work with gas tanks and can repair them.

Using a Box of Matches and an Apprentice

Although not a recommended safety practice, one person suggested using a box of matches and an apprentice to test for leaks. This method was not elaborated on further.

It is important to note that when using pressurised air or water, you should never exceed the recommended pressure for your tank, as it can cause damage. Additionally, always ensure you have the proper equipment and knowledge before attempting any of these methods.

Frequently asked questions