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How to Drain Fuel & Gas from a Generator

Learn the safe and easy steps to drain fuel from your generator. This guide covers everything from preparing your workspace to handling fuel with care.

Table of Contents

Draining the fuel tank of a portable generator is one of the most reliable ways to store your generator and ensure its longevity.

Draining gasoline from the petrol generator before storage can prevent fuel-related problems. It helps extend the life of your generator, avoid costly maintenance, and, most importantly, get it ready for the upcoming season.

This article will look at various ways to drain your BISON generator tank safely. BISON also discuss safety aspects to keep in mind before emptying the tank. Finally, BISON discuss how to store and discard the vented fuel.

how to drain fuel & gas from a generator

Do I need to drain the gasoline from the generator every time?

No, you don’t have to drain the gasoline from the portable generator if you’re adding fuel stabilizer before winterizing. However, drain the gas from the BISON generator is the surest way to prevent fuel-related problems in the long-term storage of the generator.

Drain gasoline from generator or add fuel stabilizer

No, you don’t have to drain the gasoline from the generator if you’re adding fuel stabilizer before winterizing. However, draining the gas from the BISON generator is the surest way to prevent fuel-related problems in the long-term storage of the generator.

When a generator with fuel in the tank is stored between camping seasons, the gasoline begins to degrade. Gasoline, especially ethanol-blended gasoline, easily absorbs moisture, which can lead to gas oxidation.

Over time, oxidation increases until the gas in the fuel tank becomes stale. Unchecked gums and clogging the entire fuel system can prevent the generator from starting when needed, resulting in fuel staleness.

However, if you don’t want to solve the problem of emptying the tank, you can use a fuel stabilizer to prevent oxidation. For the rest of us, however, draining the gas from the BISON generator is the safest method for long-term storage.

add fuel stabilizer to fuel

Does all the gas from the generator need to be drained?

Generators running on liquid fuels such as gasoline and diesel need to be drained or stabilized before storage. However, portable generator that run on propane do not need to go through a process of draining or stabilizing before winterizing.

Because gasoline and diesel oxidize when they come into contact with oxygen, appropriate measures must be taken during storage. Therefore, generators running on gas or diesel must be stabilized or drained.

Propane, on the other hand, is a gas that can be stored indefinitely without any problems. So dual fuel generators using propane don’t have to worry about propane going bad.

How do various kinds of generators get rid of fuel/gas?

Below is a guide on how different kinds of generators drain fuel/gas.

Safety Instructions

  • For safety purposes, the user must fully comprehend the operator’s manual before operating this product to prevent harm.
  • Ensure the engine is stopped and the spark plug wire disconnected before making any modifications to the generator.
  • Avoid burns by allowing the engine to cool down entirely before coming into contact with hot components.
  • Beware of injuries from moving parts.
  • To minimize the risk of fire or explosion, exercise caution when handling gasoline. Ensure that cigarettes, sparks, and flames are kept at a safe distance from all fuel-related components.
how to drain the gasoline from the generator

petrol/diesel generator

Locate the exhaust pipe and open the fuel valve to drain gas from the petrol generator. If your BISON petrol generator lacks a drain, use the pipe that carries the fuel from the tank to the carbonator to drain the fuel. You can also use an external fuel pump to siphon the generator’s fuel tank.

The first thing to make sure of before emptying the petrol generator’s tank is that the generator is not running and the engine is cool.

Now, put your BISON petrol generator in a well-lit area (preferably sunlight) and place it on a hard flat surface such as a concrete floor. Remove the fuel tank cap of the petrol  generator; air will be sucked in when draining the gas.

how to drain the gas from your generator-specific steps

How to Bleed Gas from a Generator – Step by Step

1. Unscrew the cap of the gas tank to facilitate airflow within the tank.

2. Locate the fuel valve switch and rotate it until it can be pushed through the plastic shield (or the maintenance cover) which safeguards the fuel lines.

3. Detach the maintenance cover by loosening the large bolts that secure it. Ensure the fuel valve is in the off position and push the valve through the cover.

4. Remove the clip located on the side of the fuel line that isn’t linked to the gas tank. Squeezing the aluminum clip should be enough for its removal. Be ready with a rag to soak up the minor amount of gas left in the tube leading to the carburetor. Detach the tube from the fuel valve, taking care not to remove or displace the tube connected to the gas tank. If this happens, gas will leak all over, leading to a messy cleanup.

5. Insert the fuel valve into a vessel that can accommodate 5-10 gallons of gas.

6. Turn the fuel valve on. Let the gas empty into the vessel until the fuel tank is depleted. Once it’s emptied, reconnect the fuel valve and fasten the cover back into its place.

7. Identify the carburetor. Usually, a screw is found at the base of the carburetor that is used to open the carburetor bowl or “float bowl.”

8. Place a container underneath the carburetor. Rotate the screw to open the drain and let the gas flow into the container (there should be just a small quantity). Once the carburetor is drained, tighten the screw again.

replace the air filter if necessary

Optional steps

1. Replace the air filter if necessary

The air filter helps prevent dust and debris from damaging the carburetor on the generator. It’s a good idea to check the air filter every year before using it for the first time and replace it if necessary. Check the air filter:

Remove the top cover of the diesel generator by loosening the two screws on either side of the unit near the top.

The air filter will be located near where you removed the screw. Carefully pull it out of its place.

If it is damaged or has any holes, you will need to replace it with a new one. If it’s clean and undamaged, push it back into place to reinstall it, making sure all four corners are properly seated in their slots.

replace spark plugs if necessary

2. Replace spark plugs if necessary

The most common reason for replacing a spark plug is that it is dirty or worn. If you don’t start the generator for a long time, the fuel in the generator may start to evaporate and leave a sticky residue. Sticky residue can cause spark plugs to stall, causing problems with the generator starting and potentially expensive repairs.

Here are the instructions for replacing the spark plugs:

First, remove the spark plug from the top of the alternator engine. You will need a wrench or socket and ratchet driver to remove the old spark plugs. After removing the old spark plug, remove any debris that may have been on the spark plug threads. Then, turn the new spark plug clockwise until it is seated in the engine.

Inverter generator

You need to remove the side cover to gain access to the fuel system, which is the case with most inverter generator. Once inside, find the fuel drain line, which goes with most inverter generators’ carburettors.

Find a fuel tank large enough to hold all the fuel in the generator fuel tank. Place the generator on a surface a little higher than the gas you will be using to drain the gas into.

Now, with the generator’s vent line positioned correctly in the fuel container, open the fuel valve to begin venting. Your fuel should now start to drain.

Some inverter generators have drain lines that connect to the carburettor. For such generators, the extra step to drain fuel from the tank is to loosen the drain screw in the carburettor.

draining gasoline from non-inverter or open-frame generators

Non-inverter or open generator

In non-inverter generators, access to the fuel lines and the carburettor is easy because most generators do not have side covers. However, most don’t even come with a fuel drain.

For generators that don’t have a dedicated fuel drain line, you can drain the gas using a carburettor or a fuel line that takes the gas from the tank to the carburettor.

With the fuel valve in the closed position, remove the clip on the fuel line connected to the carburettor. Place the tubing in a fuel container large enough to hold all the gas in the tank.

Now, open the fuel valve and wait for the generator’s fuel tank to empty. After all the gases have been drained into the fuel container, connect the fuel lines in the same way that you removed the fuel lines.

If you don’t like the idea of ​​removing the fuel lines, you can also use the carburettor drain to suck fuel from the generator tank. All you have to do is find the bleed screw on the carburettor and loosen it until the gas starts to come out.

However, venting the gas through the carburettor means you need a funnel to get to the carburettor’s bowel, which is located within the generator’s frame.

Also, you can use an external fuel transfer pump to suck the gas out of the generator. Just put one end of the pump into the generator’s fuel tank and the other into the gas tank and start the pump. Fuel will be moved from the generator to the storage container.

No matter what generator you drain, ensure to wipe up any spilled fuel and properly secure the fuel lines or carburettor screws.

what's the easiest way to empty the tank

What’s the easiest way to empty the tank?

Letting your engine burn fuel and dry your tank is the easiest way to get the gas out of your generator. It’s also the safest method because you don’t have to deal with fuel lines, highly flammable gasoline, and the hazards associated with it.

For most non-techies, removing the generator side cover and fuel line or unscrewing the carburettor drain screw can be overwhelming. For such generator owners, running the generator until the unit runs out of gas is the easiest and safest option.

Power your RV with a generator when you’re out and about, and you can easily dry-run the unit. All you have to do is fill the tank enough to run everything through the drying process.

Once the unit starves and dies, let it cool before storing it in the back of your truck or RV.

refuel the tank

Should you store or discard the fuel exhausted by your generator?

If the fuel is still fresh, you should store the drained fuel for later use. However, if the fuel is bad, make sure not to discard it on the ground, in the drainage system, or in any other body of water.

After draining the generator fuel into a container, check the fuel’s condition before storing it. The fuel is fresh if the generator was last run a day or two ago.

At this point, all you have to do to prevent fuel degradation is to add the correct fuel stabilizer to your storage container. The amount of fuel stabilizer you should use depends on factors such as the type of gas and the brand of stabilizer you have.

On the other hand, if the discharged fuel is degraded, it will have a cloudy or dark texture with a sour taste. In this case, you need to discard the fuel, as adding fuel stabilizer will not work.

However, you can’t just dump the fuel wherever you like, as the liquid is still flammable and toxic. You will need to contact your local fire department, and they will direct you to the appropriate dump.


Draining the generator prior to storage is one of the safest ways to keep your equipment trouble-free while in storage. It will prevent fuel-related issues that will prevent your generator from starting or, worse, forcing you to perform expensive maintenance or repairs.

If you’re a bit technical, you can drain the generator using a drain or fuel line. Also, you can use an external fuel transfer pump which is easier than the previous method.

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