4 Common Fuel Tank Venting Problems

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Fuel tank venting problems occur when a fuel tank is not properly vetted. Vetting helps to ensure that outside pressure on the fuel tank balances with the internal pressure.

In automobiles, fuel tanks are vetted to channel fuel vapors into the engine instead of them escaping into the atmosphere when you open the fuel tank cap.

When a fuel tank is not properly vetted, you’d most likely experience quite several issues. Hence, hereunder are the common problems with fuel tank venting you ought to know.

The best solution to these problems is to take your car to a mechanic and have the fuel tank vetted properly; this fix typically does not cost more than $200.

Common Fuel Tank Venting Problems

1. Fuel Tank Bulging (Expansion)

This is the most common scenario that could occur as a result of poor fuel tank venting or the vent valve/hose is clogged.

The bulge is due to high pressure inside the tank; venting is supposed to keep the fuel pressure inside the tank minimal and balanced with the outside pressure; so, when venting is not done properly, expansion of the fuel tank is inevitable.

2. Cracks On The Fuel Tank Cap

Fuel tank venting is done differently on different vehicles; for some vehicles (mostly vans), the venting channel is on the fuel tank cap. If your car comes with a vented fuel tank cap if for any reason you had to replace the fuel tank cap, ensure to get a vented one too.

Using an unvented fuel tank cap on such vehicles would cause the cap to crack always as pressure increases inside the tank.

So to say, if your car’s fuel tank cap keeps cracking all the time, maybe your car is meant to use a vented cap, but you’re using an unvented one; it’s not about fitting your car’s fuel tank; it’s about serving the purpose.

3. Fuel Pump Problems

A clogged or blocked fuel tank vent can lead to several fuel pump problems, such as hard starting, noise from the fuel pump/tank while driving, engine stalling due to inefficient fuel supply, and quite others.

Without proper venting, when pressure increases inside the fuel tank, it spreads to other surrounding components, and that includes the fuel pump and delivery lines.

4. Fuel Line Leaks

Again, one of the resulting scenarios from having a blocked or clogged fuel tank vent is leaks on the delivery lines. Definitely, this is the worst thing to bargain for. Leaky fuel lines should be fixed as soon as possible as it poses great danger.

The cracks on the fuel line could result from the high pressure in the unvented fuel tank. When the fuel lines crack and leak, fuel sprays out from those crack spots, and it’s very dangerous if fuel gets sprayed close to the exhaust or its components. Of course, it is never advisable to drive with leaky fuel lines.

Do Fuel Tanks Really Need To Be Vented?

Yes, fuel tanks need to be properly vented to avoid typical problems, as mentioned above. Apparently, the pressure in the gas tank increases throughout the day, whether you drive the car or not.

So, when the fuel temperature rises inside the tank, it creates vapors; these vapors are supposed to be rechanneled into the combustion chamber, and that’s what venting does. Not venting car fuel tanks can also lead to fire hazards due to fuel line leaks caused by constant high fuel pressure.

Can You Unclog a Blocked Fuel Tank Vent?

The fuel vent hose is an integral part of the fuel system in modern cars. For sure, you can unclog blocked fuel tank vents if the problem is not with the canister valve assembly. Here’s how to unclog your vehicle’s fuel vent hose.

Step 1

Connect a compressor line to the air vent line, and blow in air to check if the line is clogged. If the line is unclogged, you should hear a gurgling sound as the blown air travels into the tank, and if it’s clogged, you won’t hear such sounds.

Step 2

Disconnect the canister vent line to the gas tank and blow in air; if it’s clogged, you can easily spot that. If the line is clogged, use compressed air to thoroughly blow out the clog – this works in most cases.

Step 3

Disconnect the vent pipe and try using a small-gauge plastic tubing or a metal rod wire to push out the clog from the other open space.

If these tips don’t unclog the vent line, chances are that the problem is mechanical and should be handled by a professional auto mechanic.


These are the most common fuel tank venting problems; they can only occur when the fuel tank vent line is clogged or closed. When you notice any of these problems, it’s important that you inspect the fuel tank vent line.

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