How to clean a car fuel tank without removing it? Is it possible?

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There are many reasons as to why you would need to clean a car fuel tank without removing it. Some of the simple reasons may be you do not have a place to work on your vehicle. Or even worse, the hardware that holds the fuel tank to the vehicle looks like they are seized in place and will not come off. 

So can you clean a car fuel tank without removing it? 

I am not going to lie to you, no it is not possible. The only way to properly clean a fuel tank is by removing it from the vehicle. There is no possible way to clean your car fuel tank fully without removing it. You may be able to clean it partially but not fully. 

There are products that you can put in the tank to clean things such as varnish buildup. I will say from experience however that when these products are used, the varnish is cleaned and finds its way into your fuel filter causing even more issues. 

The only way that you would have a chance of cleaning a car fuel tank without removing it would be if it had a cleanout door. There may be a door that is located under the seat that you can open to access the fuel tank while it is still in the vehicle.

The access door would allow you to have access to clean it. This would still be a very hard process as you would need to clean it with rags by wiping it out one section at a time. 

Even if it is harder, removing the fuel tank to clean a dirty car fuel tank is a better process. 

Why should you clean your car fuel tank?

There are many situations that I have seen over the years that would require you to clean your car fuel tank. 

The most common reason is because it was filled up with the wrong type of fuel. This is very common for new diesel vehicle owners. 

When diesel owners pull up to a fuel station they sometimes forget they are driving a diesel and fill the tank with gasoline. Or worse, the full service station operator fills it with gasoline by mistake. 

Even though there are larger, more expensive components that may need replacing when this happens. Your fuel tank also needs to be drained/cleaned and refilled with the proper fuel. 

Symptoms Of A Dirty Fuel Tank

No Start: This can be a very common symptom of a fuel tank that needs cleaned. Generally a large build up of dirt/debris can cause the fuel filter to clog. This requires you to remove the fuel tank, clean it thoroughly, install a new filter sock and reinstall the tank. 

Rough Running: Noticing that your vehicle is running rough can be a symptom of a fuel tank that is full of water or contaminated. When you drive the water sloshes around and mixes with the fuel. When the fuel injector sprays fuel into the cylinder the water does not mix and causes a rough running symptom. 

Fuel Tank Tampering: Many think that this is an urban myth. An angry girlfriend/boyfriend removes the fuel tank cap and dumps sugar into the fuel tank. The sugar then clogs the fuel injectors resulting in a large repair bill for the vehicle owner. This does happen, and generally can be noticed by sugar under the fuel cap or around the fuel cap area. 

No matter the symptoms there are 3 main ways that your fuel tank can get dirty. 

Rust, dirt and water. Water is the most common reason as to why you will need to clean your fuel tank.The reason it is most common is due to the use of ethanol fuel. 

Modern fuels have roughly 10% ethanol. Ethanol is a form of alcohol and attracts moisture. Normally the moisture build up is not large enough to cause an issue. Normal driving will burn the fuel that is in the tank and the tank will then be filled regularly with new clean fuel. 

However, if the vehicle is not a daily driver water can build up in the tank. If left unchecked it can get to the point where a significant amount of water is present and the fuel tank will need to be cleaned.

Also, because of the ethanol content in the fuel it reduces the lifespan of fuel as well. Modern fuels have a shelf life of 30 days. This means if you do not use the fuel within 30 days it can cause issues to vehicles driveability. 

So if you are not going to drive the vehicle for a long period of time, leave the fuel tank empty. Or install a quality fuel additive such as STA-BIL Storage Fuel Stabilizer

How To Clean A Dirty Fuel Tank

  1. Drain the fuel tank

Run the vehicle until there is no fuel left in the tank. Or if not possible, drain fuel into a container that can be disposed of correctly according to environmental regulations.

  1. Raise vehicle

You will first need to raise the vehicle safely to access the fuel tank, hoses and wiring. Always use proper safety precautions, proper PPE and safety stands. Also remember when dealing with gasoline stay away from any source of ignition.

  1. Remove all fuel lines and wiring

There are many fuel lines attached to your fuel tank. You will need to remove the fill hose, fuel supply line, fuel return line and any EVAP lines that are attached to your fuel tank. There will also be wiring that attaches to the fuel tank sending unit and possibly the fuel level sensor. Make sure all wires are removed before you remove the tank.

  1. Remove fuel tank straps

Support the fuel tank with a gas tank tank or other lifting device so the tank is properly supported. When taking off the fuel tank straps and hardware, inspect carefully. If any of the hardware or straps look severely corroded or damaged, replace before re-installing.

  1. Lower the fuel tank carefully. 

Once the tank is on the ground, cover any open hoses with a cloth to make sure that no extra dirt finds its way into the tank. 

  1. Remove fuel sending unit

The sending unit is located inside at the top of the fuel tank, it will need to be removed to access the inside of the tank. There is a lock ring that needs to be removed before the sending unit can be removed. Be careful when removing the sending unit as it can be brittle from age or corrosion. If any damage is noticed, now is the best time to replace the sending unit before you reinstall the tank. 

  1. Pressure wash

Now that the sending unit is out you can pressure wash the inside of the tank. It is important to ensure that the tank is cleaned as much as possible. Once it is rinsed use a good multi purpose cleaner to clean any hard to remove debris.

  1. Dry tank thoroughly 

Once the tank is cleaned, dry the tank completely. There can be no water left when re-installing the tank into the vehicle. 

  1. Install new sending unit fuel sock

When the sending unit is out of the vehicle, install a new fuel filter sock onto the sending unit. If you are cleaning the fuel tank it is because the tank was dirty. Make sure you have a clean filter to prevent issues when re-installing the tank. 

  1. Re-install sending unit

Install the sending unit back into the fuel tank. I always suggest that you spray the top of the sending unit with an anti corrosion spray such as Fluid Film to keep the sending unit from rusting in the future. 

  1. Re-install the fuel tank

Install the fuel tank in the reverse of the removal steps. If any hardware or components are damaged, now is the time to replace these items when the tank is down. 

  1. Fill with fresh fuel

Make sure you fill the tank with fresh fuel. There is nothing worse than cleaning a tank, using an old jerry can of fuel to fill it and creating another dirty tank that needs to be cleaned.

If you are cleaning your fuel tank because it is full of corrosion you will need to do things a little differently. First, from my experience it is very hard to completely clean a rusty fuel tank. Once the rust starts it is almost impossible to stop.

However, if you have a fuel tank that is on a classic vehicle a replacement may be hard or impossible to find. So how do you clean a rusty fuel tank?

How to clean a rusty fuel tank?

Image of a rusty fuel tank filler neck

There is a simple method that I have used over the years to clean rusty fuel tanks. I always suggest buying a new tank if possible and only using this method if you have no other choice. 

To complete this cleaning process you will need a small amount of diesel fuel and a large amount of small nuts. Two things, very simple. 

Once the tank is drained you will try to clean as much of the rust from inside of the tank by pressure washing it clean.

After pressure washing, pour a small amount of diesel fuel in the fuel tank and a large amount of small nuts. You will then need to agitate the tank, better known as shake the living daylights out of the tank. 

After your arms feel like they are about to fall off, drain the diesel fuel and pressure wash the tank. 

Continue this process as many times as your arms can stand or until the tank is rust free. There is no easy way around cleaning a rusty fuel tank. If you have any friends who owe you a favour, now is the time to call them.

What Happens If I Do Not Dry My Fuel Tank Completely

It is very important to make sure that your fuel tank is dry before it is re-installed in the vehicle. If the fuel tank is not dry it will contain water. If there is enough water in the tank it will collect and can cause issues. 

The same issues that you may have been trying to solve in the first place. 

Hopefully now you can understand that it is very hard to clean a car fuel tank without removing it. It will be more difficult and take more time to remove it from the vehicle to clean a dirty car fuel tank but it is the best method to follow. 

It also provides the best cleaning results when finished.

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