How To Detect Clogged/Blocked Gas Tank Vent? (Symptoms)

When you notice an abnormality in your outboard motor’s performance, there can be several reasons behind that commotion, and having a Clogged/Blocked gas tank vent is one of them too.

Today’s article will help you to learn how to detect when you have a blocked gas tank vent and how you can easily fix that problem-

What Sign Of A Clogged/Blocked Gas Tank Vent?

The first and easiest sign to notice is when you visit a gas station to fill up the gas tank.

Although there can be other faults or reasons that may cause the overflow or spilling of fuel, the most common reason for this type of commotion is having a blockage in the gas tank vent.

What Are The Symptoms Of Clogged/Blocked Gas Tank Vent?

The symptoms of clogged/blocked gas or fuel tank vent on an outboard are usually similar to these following indications:

1. Overflow Or Difficulty In Filling Up Gas:

Whenever you notice overflow or spill from the gas tank while trying to fill the fuel tank mostly, it happens because of a blockage in the venting side of the gas tank or clogs in the fuel fill hose.

Since a clog or blockage causes the fuel to get trapped in the fuel line and eventually blocks the gas tank’s venting ability.

2. Vent Screen Gives Incorrect Reading & Engine Shuts Down:

Sometimes people encounter that their outboard engine abruptly shuts down without any warning and does not start again.

During further investigation, some also claim that their vent screen shows the wrong reading.

Both scenarios can happen when your gas tank not properly venting and the gas vent screen reader is also clogged.

3. Engine Gets Fuel Starved, Rough & Stalls:

A clogged gas tank vent causes the outboard engine to starve of fuel, which eventually makes the engine run rough or stall.

Especially if you own the portable gas tank on your outboard and the engine suddenly starts to run rough or struggle to start, you need to check whether the tank valve is open or not.

If that valve is not open likely, it will cause blockage on your portable gas tank, and the engine will suffer.

If you ever encounter any of these above-mentioned symptoms with your outboard motor, make sure to inspect your gas tank vent thoroughly and fix the issue. 

How Should You React If You Detect A Blocked Gas Tank Vent?

When you successfully detect that the problem arises because of the Blocked gas tank vent you have, it is time to act calmly but quickly.

Therefore, follow these below-mentioned instructions to fix the problem-

Determine The Exact Issue:

First and foremost, you need to have a thorough look at the hull’s outside to check whether the vent is even there or rusted, cracked, or upside down.

Now off the fill cap and try to blow some air into the vent to see whether the air comes out from the fill port or not. If it is not coming out the sign is clear that your vent is blocked.

Inspect The Vent Port & Replace It:

To check whether the vent port is damaged or blocked, you need to unscrew the vent or remove the vent screen and check the problem.

Now, access the backside of the vent by removing the hose and see whether the vent allows free airflow into the gas tank venting hose or the airflow gets stuck in there.

If the vent is not allowing the flow of free air, that means it is because of the blockage. In that case, you need to replace the vent port to solve the problem.

Clean Gas Tank Vent Reading Screen:

If your gas tank vent also has that fine-wire screens for showing the reading rates, and it started to show wrong reading, that means the vent reading screen got clogged.

Over time, the vent screen gets covered with build-up corrosion, grime, or salt crystals, which prevents the vent from breathing properly.

Therefore, use a small wire brush to clean that clogged screen before it gets corroded with corrosion fully.

But if you observe that the corrosion has corroded away at the screen, an immediate solution is to replace the vent.

Inspect & Replace The Fuel Surge Protector:

If your gas tank contains a fuel surge protector, commonly known as a no-spill valve too, it will prevent gas from spewing out of the vent and hull to get stained.

However, over time, when these valves or protectors get old, they can malfunction too. Especially, when the gummy fuel debris or residue causes those valves to prevent the gas tank vent from functioning correctly.

Therefore, inspect the fuel surge protector by shaking and observe whether the ball inside the valve rattle immediately or not. If not, you need to change the valve.

Is Fixing Clogged/Blocked Gas Tank Vent Typically Expensive?

Technically, the expense or costing may vary based on the damage level. For example, if the damage only requires cleaning the screen or vent area, it will not be a costly, and you can even do that by yourself. So, you do not have to worry about any extra labor costs.

But if your vent system requires more than just cleaning, such as replacing the clamp, valve, or port, then you have to spend a little more buck.

In that case, if you do not know how to install those parts, that will add up the labor cost for hiring a professional.

However, if you notice that the damage is serious, better consult with an expert or take help from the professionals.

How Often Should You Check On Your Gas Tank Vent?

The direct and easy way to do that is checking on the gas tank vent system before you plan to fill up the gas.

I am saying the vent system because you need to inspect everything thoroughly to find any vent-related fault there, such as checking the main fuel or gas line, vent port, the valve, vent reading screen, etc.

To stay on the safe side, maintain a regular inspection of the gas tank vent, just as you do the outboard motor and other essential parts required servicing.

Final Thoughts

When your gas tank is not venting properly, it can cause your engine to run rough, idle, or stall and eventually force the engine to shut down.

That is the worst scenario, and you can easily avoid encountering such incidents when you know the symptoms to detect whether your gas tank vent is blocked or not.

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