Fuel Tank Pressure: Can-Am Performance And Safety

Owners of Can-Am vehicles have reported issues with pressure in their fuel tanks. Some have observed that their fuel tanks build up excessive pressure, resulting in a hissing or whistling sound when the cap is removed. This pressure release is often accompanied by the sound of air rushing in and, in some cases, liquid fuel spraying from the cap. While a little pressure is considered normal, the concern arises when the pressure becomes excessive, leading to potential vapor lock and strain on the fuel pump.

Several factors can contribute to the pressure build-up in Can-Am fuel tanks. One factor is the cycling of fuel to and from the engine, which causes the fuel to heat up and expand, leading to increased pressure. Additionally, the design of the fuel tank and ventilation system can play a role. Some models have a one-way breather valve that may become stuck shut, preventing proper ventilation and contributing to pressure build-up.

To address the issue of excessive pressure, some owners have suggested checking for clogged or jammed lines and ensuring that the breather valve is functioning correctly. Others have recommended running a vent line directly from the tank to improve ventilation and reduce pressure. It is also important to monitor fuel pressure and ensure that it remains within the optimal range for the vehicle's performance.

Fuel tank pressure release when removing the cap

It is common for there to be some pressure release when removing the fuel cap from a Can-Am vehicle. This is due to the one-way valve in the tank, which lets air in as the fuel is used, creating positive pressure. This is a normal function, and some pressure release is to be expected.

However, excessive pressure can cause issues, such as vapor lock, which can put a strain on the fuel pump and cause the vehicle to stall. This can be caused by a clogged fuel vent line, which can be due to mud or other foreign objects, or a bad installation. If you suspect this to be the case, it is recommended to check the fuel vent line for any blockages.

Another potential cause of excessive pressure is the fuel boiling inside the tank on hot days. This could be due to the fuel lines running too close to the headers, causing them to heat up. It could also be due to the fuel having a low boiling point.

If you are experiencing issues with fuel tank pressure, it is recommended to consult a mechanic or a Can-Am dealership for further advice and potential solutions.

One-way valve and negative pressure

The fuel tank in a Can-Am vehicle should not be building pressure. However, a little pressure is fine and normal. The tank has a one-way valve to let air in as the fuel is used; otherwise, it would create negative pressure at the fuel pump inlet. This one-way valve also prevents fuel vapors from escaping into the atmosphere.

The "whoosh" sound heard when taking off the gas cap is due to the pressure in the tank. It is normal, and the vapors are explosive, but it would take deliberate action or extreme negligence to cause an explosion from the cap venting vapors. The gas cap is designed to allow a certain amount of pressure/vacuum before opening up to prevent damage from excessive pressure/vacuum.

If there is too much pressure in the tank, it could indicate that the one-way breather valve is stuck shut. This valve should be located near the fuel pump, under the seat.

To address the issue of negative pressure in the fuel tank, one possible solution is to remove the check valve setup and run a vent line up to the pod with a small inline filter. This modification ensures that the tank can breathe and prevents the possibility of a vacuum lock.

Fuel pump issues

Unusual Noises

A damaged fuel pump may emit a loud, whining noise, indicating that it is working harder to deliver fuel. This noise can also be caused by low fuel or contaminated fuel. If you hear this noise, it's best to consult a mechanic.

Engine Sputtering

Engine sputtering, or jerking, during high speeds is often a sign of a failing fuel pump. This is caused by an inconsistent flow of fuel to the engine, which can be due to a weak fuel pump or a clogged fuel filter.

Power Loss

A faulty fuel pump may cause your vehicle to lose power while accelerating or driving uphill/carrying heavy loads. This is because the fuel pump cannot keep up with the engine's demand for fuel at higher speeds or under stress.

Car Not Starting

If your car won't start, it could be due to a faulty fuel pump that is unable to deliver fuel to the engine. However, there could be other reasons for this issue, such as electrical faults or problems with the ignition switch, so it's important to rule those out first.

Poor Fuel Efficiency

If you notice a significant decrease in your vehicle's fuel efficiency, it could be due to a failing fuel pump. This is because a faulty pump may consume more power, resulting in increased fuel consumption.

Stalling

A faulty fuel pump can cause your engine to stall unexpectedly, especially at high temperatures. This is often due to the pump struggling to supply enough fuel to the engine when it's hot.

Surging Engine Performance

A faulty fuel pump can cause the engine to surge forward for no apparent reason. This is due to the pump delivering too much fuel, resulting in fluctuating vehicle speeds.

Overheating

If your fuel pump is not constantly submerged in fuel, it can overheat and fail. This is because fuel acts as a coolant for the electric motor in the fuel pump. Repeatedly running your fuel tank low can cause the fuel to superheat and damage the pump.

Low Voltage

Low voltage to the pump can cause a drop in fuel pressure and affect the fuel supply to the engine. This can be due to issues such as a broken wire connection or a weak battery.

Clogged Fuel Filters

Over time, fuel filters can become clogged with dirt and debris, affecting the flow of fuel and the performance of the fuel pump and injectors. Regular cleaning or replacement of fuel filters is important to maintain optimal fuel delivery.

Defective Fuel Pressure Regulator

The fuel pressure regulator ensures proper fuel supply to the injectors by maintaining the correct pressure. Any issues with this component, such as fuel leaks or internal failures, can negatively impact engine performance.

Fuel Pump Relay Issues

The relay is an electronic switch that controls the current passing to the fuel pump. If it is defective, it can cut off power to the pump, causing the engine to stall.

Hissing and pressure in the gas tank

One-Way Breather Valve Issue:

The hissing sound could be due to a stuck one-way breather valve, which is located near the fuel pump. This valve allows air to enter the tank as fuel is used, preventing negative pressure from building up. When it malfunctions, pressure can build up, causing the hissing noise when the cap is opened.

Pressure Relief Valve Activation:

Propane or pressurised gas tanks often have a pressure relief valve designed to release excess pressure. If your gas tank is overfilled or subjected to high temperatures, this valve may activate, resulting in a hissing sound as it releases the built-up pressure. This is a safety feature to prevent tank ruptures and is not typically a cause for concern.

Leaks or Loose Connections:

A hissing sound could indicate a leak or loose connection in the fuel system. Check the hose, connections, and regulator for any signs of damage or wear and tear. A small leak can not only cause a hissing noise but also pose a safety hazard if not addressed promptly.

Temperature Fluctuations:

High temperatures can cause the fuel to expand, leading to increased pressure. This is more common in hotter climates or when the vehicle is parked in direct sunlight. As a result, you may experience pressure and hissing when opening the gas cap.

Fuel Evaporation:

In modern cars, evaporated fuel vapors are typically handled by the EVAP system, which stores the vapors in a canister for later burning in the engine. However, very high ambient temperatures can lead to accelerated fuel evaporation, potentially causing the hissing sound and vapour haze you observed.

Blockage in Vent Line:

If the hissing is accompanied by a sudden loss of power, it could be due to a clogged fuel vent line. As the fuel level decreases, air needs to enter the tank to replace the used fuel. If the vent line is blocked, a vacuum can form in the tank, leading to increased strain on the fuel pump.

If you experience hissing and pressure in your gas tank, it is important to inspect your vehicle and address any potential issues promptly. Some of these issues can be easily resolved, while others may require professional assistance.

Fuel boiling in the tank

When the engine is running, fuel is cycled to and from the tank, and this movement can cause the fuel to heat up. In hotter climates, the fuel is more likely to be affected by the engine's heat, and the warmer climate will also raise the ambient temperature of the fuel. As the temperature of the fuel rises, it will begin to boil, and this is more likely to occur at higher altitudes where the air pressure is lower.

Additionally, if the fuel lines are routed too close to heat sources, such as the exhaust or the engine, this can further contribute to the problem. The returning fuel can also be exposed to heated air, which raises the temperature further.

Some vehicles are more prone to this issue than others, and it may be a design flaw in certain cases. It is important to ensure that the fuel system is sealed properly to maintain pressure and prevent boiling.

If you experience fuel boiling, it is recommended to check the venting system for blockages and ensure that the fuel lines are routed away from heat sources as much as possible. Insulating the fuel tank and fuel lines with heat tape or reflective materials can also help mitigate the issue.

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