How To Empty Fuel Tank On A Car

Let's face it, there are a few reasons why you might need to empty the fuel tank on your car. Maybe you accidentally put the wrong type of fuel in (petrol in a diesel or vice versa), your fuel has gone bad after sitting for a long time, or you're prepping the vehicle for long-term storage or even scrap. Whatever the reason, safely and effectively emptying the tank is crucial. Incorrect methods can damage your car, cause a fire hazard, or even harm yourself. This article will guide you through the process, explaining why it's important and how to do it right.

Why Emptying Your Fuel Tank Matters

The most common reason for needing to drain a fuel tank is fuel contamination. Putting the wrong fuel in your car can cause serious engine damage. Even if you only added a small amount of the wrong fuel, it's best to remove it before starting the engine. Stale fuel is another culprit. Gasoline can degrade over time, especially if left sitting in the tank for several months. This stale fuel can clog fuel lines, injectors, and even damage the fuel pump. Finally, if preparing a car for long-term storage, removing the fuel helps prevent corrosion and the formation of gum and varnish inside the fuel system.

Recognizing the Symptoms

Knowing when you need to drain your fuel tank is important. Here are some tell-tale signs:

Wrong Fuel in the Tank: This is the most obvious. If you filled up with the wrong fuel, don't start the engine.
Engine Runs Poorly or Not At All: If you accidentally drove with the wrong fuel or stale fuel, the engine might run rough, misfire, stall frequently, or refuse to start at all.
Fuel Smell: A strong, unusual fuel smell could indicate fuel degradation or a leak in the fuel system caused by contaminated or old fuel.
Visible Fuel Contamination: If you can see the fuel in the tank (some vehicles have a drain plug that allows for a small sample), check for discoloration, sediment, or water.
Vehicle Has Been Stored Long-Term: If a car has been sitting for months or years, the fuel is likely stale and needs to be removed.

Understanding the Root Cause

Fuel tanks are designed to store fuel safely and prevent leaks. However, problems can arise. Introducing the wrong fuel, like petrol into a diesel engine, messes with the combustion process. Diesel relies on compression ignition, while petrol needs a spark. The petrol disrupts the diesel's combustion. Stale fuel, on the other hand, undergoes a process called oxidation. The volatile components evaporate, leaving behind a gummy residue that can clog the fuel system. Water can also enter the tank through condensation or a faulty fuel cap, leading to rust and corrosion. Even the materials used in fuel tanks can degrade over time, especially with older vehicles. Newer vehicles often have plastic fuel tanks which are less prone to rust, but they can still be damaged by certain fuel additives or contaminants.

The Potential Consequences of Ignoring the Problem

Ignoring a contaminated fuel tank can lead to a cascade of problems:

Engine Damage: Running the wrong fuel can cause serious and costly engine damage, especially in diesel engines. Petrol in a diesel engine can damage the fuel pump, injectors, and even the engine block.
Fuel System Damage: Stale fuel can clog fuel lines, fuel filters, fuel pumps, and fuel injectors, requiring expensive repairs or replacements.
Reduced Fuel Efficiency: Even slightly degraded fuel can reduce fuel efficiency and engine performance.
Starting Problems: A clogged fuel system can make it difficult or impossible to start the engine.
Increased Emissions: A poorly running engine due to contaminated fuel can increase harmful emissions.

Recommended Fixes: Draining the Fuel Tank

There are two primary methods for draining a fuel tank. Safety is paramount, so always work in a well-ventilated area, disconnect the negative battery cable, and have a fire extinguisher nearby. Never smoke or use open flames during this procedure.

Method 1: Using a Siphon Pump

Gather Your Supplies: You'll need a siphon pump (manual or electric), a clean fuel-resistant container (at least the size of your fuel tank), safety glasses, gloves, and rags.
Access the Fuel Tank: In most vehicles, you can access the fuel tank through the filler neck. Remove the fuel cap.
Insert the Siphon Hose: Carefully insert the siphon hose into the fuel tank through the filler neck. Be sure to guide the hose past any anti-siphon devices (if present). Sometimes, a long, flexible screwdriver can help push the hose past these devices.
Start Siphoning: If using a manual pump, follow the pump's instructions to start the siphon. If using an electric pump, simply turn it on.
Monitor the Flow: Keep a close eye on the fuel flow and the container to prevent spills.
Empty the Tank: Continue siphoning until the tank is empty.
Proper Disposal: Dispose of the old fuel properly at a hazardous waste disposal facility or recycling center. Do not pour it down the drain or onto the ground.

Method 2: Using the Fuel Pump Access

This method involves accessing the fuel pump directly. This is often a faster method, but can be slightly more involved.

Locate the Fuel Pump Access Panel: This is usually located under the rear seat or in the trunk. Consult your vehicle's repair manual for the exact location.
Remove the Access Panel: Remove the screws or clips holding the access panel in place.
Disconnect the Fuel Pump Electrical Connector: Disconnect the electrical connector to the fuel pump.
Identify the Fuel Lines: Identify the fuel supply and return lines connected to the fuel pump module. Usually, the supply line is the one delivering fuel to the engine and has higher pressure.
Disconnect the Fuel Supply Line: Carefully disconnect the fuel supply line. Be prepared for some fuel to spill out, so have rags ready.
Attach a Hose: Attach a fuel-resistant hose to the fuel supply line fitting.
Run the Hose to a Container: Place the other end of the hose into a clean fuel-resistant container.
Energize the Fuel Pump Briefly: Briefly reconnect the fuel pump electrical connector to activate the pump and start draining the fuel. Only energize it in short bursts (a few seconds at a time) to avoid overheating the pump. Disconnect the connector each time to pause the flow.
Empty the Tank: Repeat the process until the tank is empty.
Reassemble: Disconnect the hose, reconnect the fuel line, reconnect the fuel pump electrical connector, replace the access panel, and reinstall the rear seat or trunk lining.
Proper Disposal: Dispose of the old fuel properly.

Important Considerations

Fuel Tank Design: Some vehicles have complex fuel tank designs with internal baffles that can make siphoning difficult.
Anti-Siphon Devices: Many modern vehicles have anti-siphon devices in the filler neck to prevent fuel theft. These can make it difficult to insert a siphon hose.
Fuel Pump Condition: If the fuel pump is faulty, it may not be able to pump fuel effectively.
Safety Precautions: Always prioritize safety when working with fuel. Wear safety glasses and gloves, work in a well-ventilated area, and have a fire extinguisher nearby.

Cost Estimates and Shop Advice

If you're not comfortable draining the fuel tank yourself, it's best to take your car to a qualified mechanic. The cost to have a shop drain your fuel tank can vary depending on the vehicle and the shop's labor rate. Generally, you can expect to pay between $100 and $300 for this service. This usually includes the cost of disposing of the old fuel. If the mechanic identifies other problems related to fuel contamination (e.g., clogged fuel filter, damaged fuel pump), the cost will be higher.

Before taking your car to a shop, be sure to explain the situation clearly. Tell them that you need the fuel tank drained because of contaminated fuel. Ask for a written estimate before they begin any work. Also, inquire about their disposal methods for the old fuel. A reputable shop will follow proper environmental regulations for fuel disposal.

While there aren't specific TSBs (Technical Service Bulletins) solely dedicated to "draining fuel tanks," there *are* TSBs related to fuel contamination, fuel system cleaning, and fuel pump replacement that might be relevant depending on the reason for draining the tank. For example, if you put petrol in a diesel, searching for TSBs related to "misfueling diesel" for your specific vehicle make and model could provide valuable information on recommended procedures and potential damage.

Ultimately, safely and effectively draining your car's fuel tank can prevent serious engine damage and costly repairs. By understanding the potential problems, following the recommended procedures, and prioritizing safety, you can handle this task yourself or confidently seek professional assistance.