How to Drain a Mercedes Sprinter Fuel Tank

You put the wrong fuel in your van. Now you need to get it out fast. Do not start the engine, or you might ruin the pump. I will show you how to safely empty that tank so you can get back on the road without a massive repair bill today.

You need to access the fuel sending unit under the floor. Pull the mat and cut the carpet to find the cover plate. Open it up, disconnect the lines, and use a pump to draw the fuel out. This is the only way to avoid a huge mess or broken parts.

Reasons to Empty the Tank

Most people drain a tank because they put gas in a diesel engine. This mistake is common, but it causes real damage to your fuel system. You must act fast to save your engine from long term wear. Follow these steps to clear the lines and start fresh.

The Wrong Fuel

Putting gas in a diesel engine is a classic error. The gas acts like a solvent and strips oil away from parts. This creates friction, which destroys the high pressure pump. You must drain every drop of the bad fuel before you turn that key in the ignition.

A Contaminated Fuel Supply

Sometimes you fill up at a station with a bad tank. Dirt or water gets into your fuel. This clogs the filters and ruins the injectors. You might notice the van sputter. It is time to pull the bad fuel out and clean the entire system for safety.

The Long Term Storage

Maybe you left your van sit for many months. The old diesel turns into a thick sludge. This goo clogs the lines and sits in the tank. It is impossible for the engine to run on this mess. You have to remove the old fuel to start.

The Faulty Fuel Sender

Your gauge says empty, but the tank is full. Or the gauge acts wild while you drive. You need to pull the sender unit out to check the float. Draining the tank makes this job easy. You can see the parts clearly without any spilled fuel around.

A Damaged Tank Wall

Small cracks or leaks appear over time. You might need to drop the tank to patch a hole. You cannot drop a heavy tank full of fuel. Drain it first to save your back. Work becomes simple when the weight is gone and the area is dry.

A Failed Internal Pump

The pump sits inside the tank on most models. It fails when it gets old or hot. You have to remove the old fuel to reach the pump assembly. This job requires patience and a clean space. Keep everything organized so you do not lose the small screws.

Do not rush the job, and always watch for leaks near the lines. Clean the area before you open the tank to keep dirt out of the system.

• Wear thick gloves
• Use a plastic bucket
• Check for open flames
• Keep a fire extinguisher
• Disconnect the battery
• Cover the open hole

How to Drain a Mercedes Sprinter Fuel Tank

Accessing the tank is the first real challenge. You must find the panel under the carpet to see the top of the fuel pump assembly.

The Access Panel

Remove the passenger seat or the floor mat to reach the metal plate. You will see several screws holding it down. Use a screwdriver to lift the plate away from the floor.

Be careful not to cut any wires under the carpet. The fuel lines stay under pressure, so wrap a rag around the connection points before you pull them off.

Once the plate is off, you see the top of the tank. Clean all the dirt from the edges. You do not want any grit falling inside the tank.

The Fuel Lines

Carefully unplug the electrical connector first. Push the release tab and pull the plug away. Do not yank it too hard, as the plastic gets brittle.

Find the fuel supply and return lines. Squeeze the clips and pull them off. A small amount of fuel will drip out, so be ready with a towel.

Plug the lines with a small bolt if you can. This keeps the lines clean while you work. Do not let any dirt get into the open fuel hoses.

The Locking Ring

The pump is held by a large plastic ring. You will need a special tool or a hammer and punch. Tap the tabs gently to turn the ring left.

Do not use a metal hammer directly on the ring. It will crack the plastic. Use a block of wood to push against the tabs as you turn.

Once the ring is loose, lift it off the tank. Be ready to pull the entire assembly out. The pump is attached to the fuel level float arm.

The Siphon Process

Insert a clean hose into the hole. Use a manual pump to move the fuel into a storage container. Do not use your mouth to start the flow.

Keep the hose moving to reach the low spots in the tank. You want to get as much of the bad fuel out as possible. This prevents mixing issues.

Check the bottom of the tank with a flashlight. If you see debris, you should wipe it out with a lint-free cloth. Do not use paper towels.

The Internal Inspection

Look at the filter screen on the pump. If it looks dark or clogged, clean it with fresh fuel. This screen keeps the pump from burning out.

Check the wires for any signs of heat damage. If the wires look melted, you need to replace the pump assembly. A bad wire causes failure.

Make sure the rubber seal for the tank lid is clean. If it looks flat or cracked, buy a new one. This prevents fuel smells inside.

The Reassembly

Put the pump assembly back into the tank. Line up the tabs so it sits flush. Press the rubber seal down so it stays in place.

Screw the locking ring on by hand first. Tighten it with your tool until it is snug. Do not overtighten it or the plastic might split.

Reconnect the fuel lines and the electrical plug. Listen for a click on the lines. That click confirms the seal is tight and ready for use.

Replacing the fuel system parts is a messy job, but you can save a lot of cash by doing it yourself. Just keep your work area clean and store the old fuel in a safe container that does not leak.

• Use a steady pump
• Keep the garage ventilated
• Check the O-ring seal
• Work on a level surface
• Label every fuel line
• Replace the locking ring

Is There a Drain Plug?

Many people look for a bolt at the bottom of the tank. The Sprinter does not have a drain plug. You must pull the pump unit to get the fuel out. It seems like a pain, but it is standard for these vans. Do not try to drill a hole in the tank.

You might want to drill a hole to save time. This is a huge mistake. The plastic tank is thin and it will crack. You will never get the seal perfect again. Always take the time to pull the unit from the top. It is safer for your van and your home.

The fuel tank sits between the frame rails. It is tucked up high for safety. This design keeps it away from road debris. You cannot reach the bottom from the ground. Removing the seat and floor panel is the only way to get inside. It takes a few minutes but works perfectly.

If you really need to empty the tank often, buy a better siphon tool. A high quality manual pump makes the job go much faster. You can reach deep into the corners of the tank with a thin hose. It makes the whole process much easier for any home mechanic to handle.

• No bottom drain plug
• Plastic is easily damaged
• Top access is required
• Siphon is your friend
• Keep tools nearby
• Never drill the tank

Will the Engine Run on Bad Fuel?

You should never try to start the engine if you have the wrong fuel. The high pressure system in a diesel Sprinter is very sensitive. Even a small amount of gas causes major damage to the injectors. The parts cost a lot of money to replace. It is not worth the risk.

If you turned the key by accident, stop right there. Do not try to drive it home. Call a tow truck to take the van to your shop. The fuel has already moved into the lines. You need a full flush of the fuel rails to save your expensive engine parts.

Most mechanics see this mistake once a week. They know exactly how to fix it. If you try to run it, the pump grinds itself to bits. The metal shavings move into the injectors and clog them. A simple drain becomes a full system overhaul. Save your money and stop immediately.

Diesel fuel provides lubrication for the pump. Gas removes that oil. Without the oil, the metal parts rub together and create heat. The pump fails in minutes. You will hear a loud noise if it happens while driving. That sound means your wallet is about to take a hit.

• Gas destroys diesel pumps
• Stop if you notice
• Do not turn the key
• Tow the van away
• Flush the lines deep
• Save the injectors

What Happens to the Old Fuel?

You have a bucket of bad fuel. You cannot dump it down the drain or on the grass. It is toxic and hurts the environment. Take it to a local shop that recycles oil. They have tanks for this. It is the right thing to do for your neighborhood and water supply.

Many auto parts stores take old oil and fuel. Call them before you drive over. Ask if they have space in their tank. Most will say yes. It is a free service in many towns. Just make sure the container has a good lid so it does not spill in your car.

Do not try to burn the bad fuel in a fire pit. It creates toxic smoke and stays in the ground for years. It is a fire hazard for your property. Just keep it in a sealed jug until you find a proper place to drop it off. It is easy.

Think about the next person who might touch that fuel. Label the jug clearly. Write “Bad Diesel” or “Mixed Fuel” on the side. This prevents someone from accidentally putting it back in a car. Accidents happen when containers are not marked. Keep it safe and keep it simple for everyone.

• Use proper disposal sites
• Label your fuel jugs
• Never pour on ground
• Check local shop rules
• Keep lids very tight
• Do not burn fuel

Can I Save the Fuel?

If you only have a little bit of gas mixed in, you might think you can filter it out. You cannot. Diesel and gas mix together fast. They do not separate like oil and water. There is no filter that can pull gas out of diesel. Once it is mixed, it is ruined.

Do not try to use the fuel in a lawn mower or heater. The mixture will damage those engines too. The chemical properties of the fuel are changed forever. It is better to get rid of it than to risk breaking more equipment. It is not worth the cost of a mower.

Some people sell old fuel to others, but that is a bad idea. You might cause someone else to have a breakdown. Be honest about what is in the jug. If it is bad, it is trash. Most recyclers will take it regardless of the mix. Just get it off your property.

Clean fuel is the lifeblood of your van. If you take care of the system, your Sprinter will run for many miles. Cutting corners with bad fuel always ends in a tow truck bill. Trust your gut and start with a clean tank every single time you have an issue.

• Never mix gas back
• Filters cannot fix it
• Do not use tools
• Destroy the bad batch
• Start with fresh fuel
• Protect your engine

Final Thoughts

I hope this guide helps you get your van back in shape. Working on a fuel tank is never fun, but it is very satisfying to finish it yourself. Just remember to work slowly and keep your eyes on the details. You can handle this job with the right tools. Take your time, stay safe, and you will have that tank drained in no time.

Frequently Asked Questions

Is It Safe to Drain the Tank Indoors?

No, never work on a fuel tank inside a closed garage. The fumes build up fast and can cause a fire if a spark happens. Always work in a well ventilated area or outside to keep the air clean and safe for you to breathe while you work on the van.

Can I Use a Drill to Speed Up the Job?

Absolutely not. You must never drill into a fuel tank. The plastic is thin and the risk of fire or permanent damage is too high. Always use the access panel under the seat to reach the fuel inside. Drilling will only result in a very expensive replacement tank for your van.

Are There Any Special Tools I Need?

You need a basic socket set to remove the floor panels. A manual siphon pump is essential to pull the fuel out through the top opening. You might also want a hammer and a piece of wood to tap the locking ring, but you do not need any fancy equipment.

Do I Need to Disconnect the Battery?

Yes, you must disconnect the battery before you open the fuel tank. This prevents any accidental sparks from the pump wires. Electricity and fuel are a dangerous mix. Taking ten seconds to pull the negative cable gives you peace of mind while you work inside the van’s cabin today.

Should I Replace the O-ring Seal?

If the old seal looks flat or has any cracks, you should replace it. A bad seal leads to fuel smells inside the cabin while you drive. It is a very cheap part that keeps your van smelling clean. Always check the condition of the rubber before you lock it down.

Will the Engine Start Immediately After Draining?

The engine might take a few tries to start because there is air in the fuel lines. Turn the key to the on position for a few seconds to let the pump build pressure. Do this a few times before you crank the engine to help the system prime itself.

Can I Keep the Old Fuel for Later?

You should not keep bad fuel, especially if it is mixed with gas. It will not work well in any engine and it is a fire hazard in your storage area. Take it to a local recycling center right away to keep your home safe and clean for everyone.

Does the Sprinter Have a Fuel Filter I Should Change?

Yes, it is a great idea to change the fuel filter after you drain the tank. If you had bad fuel or debris in the system, the old filter is likely clogged. A new filter protects your expensive injectors and keeps the engine running smoothly for many miles to come.