Rajan Wilcox
DEF, or diesel exhaust fluid, is composed of urea and water, and even a small amount of it in a diesel tank will contaminate the diesel. DEF contamination can cause severe performance issues and engine seizure. If you suspect DEF contamination in your diesel engine, do not drive the vehicle or start the engine. Instead, change the fuel filters immediately and flush the entire fuel system. Depending on the extent of contamination, you may need to replace parts of the fuel system, such as the tank, lines, pumps, and injectors.
How to remove DEF from diesel fuel
| Characteristics | Values |
|---|---|
| What is DEF? | Diesel Exhaust Fluid, consisting of 32.5% synthetic urea and 67.5% deionized water |
| What happens when DEF is added to a diesel tank? | The diesel fuel is contaminated and if the engine is started, the DEF can cause damage to the fuel system |
| What should you do if DEF is added to a diesel tank? | Do not drive or start the engine. Change the fuel filters and flush the entire fuel system. Some parts may need to be repaired or replaced. |
| What are the signs of DEF contamination? | The vehicle may hesitate, experience problems accelerating, sputter, rev, or jolt to a start. |
| What are the potential consequences of DEF contamination? | Increased stress on injectors, failure of injectors, inhibition of fuel pump lubrication, sludge formation, and engine seizure |
| Can DEF-contaminated fuel systems be repaired? | Yes, but it is expensive. Plastic fuel tanks can be flushed and reused, but other components must be replaced due to DEF's corrosive nature. |
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What You'll Learn
Do not drive or start the engine
If you have accidentally put DEF in your diesel tank, it is important to know that even a small amount will contaminate your diesel fuel. DEF is composed of urea and water, and it is corrosive and harmful to several metals, including carbon steel, brass, aluminium, copper, magnesium, nickel, and zinc.
If you have put DEF in your diesel tank, do not drive or start the engine. The consequences of driving with DEF in your diesel tank can be severe and expensive. DEF contamination generates greater stress on the injectors and could result in failure. If you start the engine, the key will be turned on, and DEF will be forced further into the fuel lines. Faulty gaskets along the fuel system can cause DEF to leak into the oil sump, creating sludge and affecting the lubrication of the engine. This can cause engine seizure.
If the engine is started and introduces the diesel and DEF mixture, longer-term consequences will occur. DEF will not only contaminate the diesel, but it will also cause damage to the fuel system if not removed. If the engine does start, you will likely experience severe performance issues. The vehicle may hesitate or experience problems accelerating. This is because the injectors have water-based DEF being sucked into the system, causing trouble with combustion.
If you have accidentally put DEF in your diesel tank, do not drive or start the engine. Instead, change the fuel filters immediately and flush your entire fuel system. Depending on the circumstances and the advice of diesel mechanics, you may need to replace some parts.
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$74.84
Replace the fuel filters
If your diesel fuel tank has been contaminated with DEF, the fuel filters must be replaced along with their filter housings. This is because DEF is corrosive and abrasive, and can cause severe damage to the fuel system. Urea crystals form as the water in DEF evaporates, and these crystals are extremely damaging to high-pressure injectors.
It is important to note that attempting to clean and reuse the fuel filters is not advisable, as the corrosive nature of DEF means that they must be replaced with new or quality reman parts. The small cost of new housing is insignificant compared to the cost of replacing the entire fuel system a second time.
When replacing the fuel filters, it is important to follow the correct procedure and take appropriate safety precautions. It is recommended that you refer to the specific instructions provided by the manufacturer of your vehicle or a qualified mechanic.
In general, the process of replacing fuel filters typically involves locating and accessing the fuel filter housing, which is usually located near the fuel tank or along the fuel line. Once the housing is accessed, the old fuel filter can be removed and replaced with a new one. It is important to ensure that the new fuel filter is securely installed and that any necessary maintenance procedures, such as priming or bleeding the fuel system, are performed before starting the vehicle.
It is worth noting that fuel filters should be regularly inspected and replaced as part of routine maintenance, even if your diesel fuel has not been contaminated with DEF. This will help to ensure optimal fuel system performance and prevent unexpected issues.
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Flush the entire fuel system
If you suspect DEF contamination in your diesel engine, it is crucial to act promptly. DEF (Diesel Exhaust Fluid) consists of 32.5% high-purity synthetic urea and 67.5% deionized water. It is corrosive and can cause severe damage to the fuel system, including injector failure, clogged fuel lines, and pump failure. Therefore, flushing the entire fuel system is necessary to prevent further issues and ensure the engine's performance and reliability.
Flushing the entire fuel system involves removing all contaminated fuel and thoroughly cleaning the system. Here is a step-by-step guide to flushing the entire fuel system:
Step 1: Stop the Vehicle and Do Not Turn on the Ignition
If you suspect or notice any signs of DEF contamination, such as hard starting, rough idle, smoking exhaust, decreased engine performance, unusual noises, or warning lights, immediately stop driving the vehicle. Do not turn on the ignition, as this may energize the fuel system and pump the contaminated fuel into other parts of the engine.
Step 2: Tow the Vehicle to a Repair Facility or Mechanic
Have the vehicle towed to a repair facility or a qualified mechanic as soon as possible. Do not attempt to drive the vehicle, as it may cause further damage. Make sure to disconnect the batteries before towing to prevent any accidental activation of the fuel pump.
Step 3: Drain the Fuel Tank
The mechanic will then need to drain the fuel tank completely. This step involves dropping the fuel tank and removing all the contaminated fuel, ensuring that none of it remains in the tank.
Step 4: Flush the Fuel System
After draining the tank, the mechanic will flush the entire fuel system, including the injectors, fuel lines, pump, and tank. This process ensures that any traces of DEF are eliminated from the system. It is a meticulous and professional process that requires expertise and specialized equipment.
Step 5: Refill with Clean Diesel Fuel
Once the fuel system is thoroughly flushed, it is essential to refill the tank with clean diesel fuel. This step helps dilute any remaining DEF traces and ensures that your engine runs smoothly without any adverse effects.
Step 6: Replace Damaged Components
Depending on the extent of DEF contamination and the damage caused, the mechanic may need to replace certain components of the fuel system. Plastic fuel tanks can usually be flushed and reused, but other parts, such as the fuel cooler and injectors, may need to be replaced due to DEF's corrosive nature.
Remember, it is always best to seek expert help when dealing with DEF contamination. Prevention is also crucial, so always store DEF and diesel fuel in separate containers, clearly labelled, and double-check before adding anything to your vehicle.
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Repair or replace affected parts
If you've accidentally added DEF to your diesel fuel tank, it is important to act quickly to prevent extensive damage to your vehicle. DEF, or Diesel Exhaust Fluid, is corrosive and harmful to several metals, including carbon steel, brass, aluminium, copper, magnesium, nickel, and zinc.
The first step is to ensure your safety and that of your vehicle. Secure your vehicle away from traffic or potential hazards. Do not attempt to drive the vehicle or start the engine. Have the vehicle towed to a repair facility.
Next, you'll need to drain the contaminated fuel from the tank. This is best left to professionals as it is a complex procedure that requires expertise and specialised equipment to avoid further damage to your vehicle and for the proper disposal of the contaminated fuel.
Once the tank has been drained, the entire fuel system, including the tank, lines, pumps, housings, and injectors, may need to be replaced, especially if the DEF has been introduced into the engine. Plastic fuel tanks can usually be flushed and reused, but the rest of the system must typically be replaced due to DEF's corrosive nature.
Other components that may need to be replaced or cleaned include the fuel cooler, the fuel filter, sensors, and lines. The DEF injector may also need replacing if it has been contaminated.
Finally, refill the system with high-quality DEF to ensure proper functioning, checking that the tank is filled to the correct level and that there are no leaks. Some vehicles may require a system reset to clear any error codes triggered by the contamination.
To prevent DEF contamination in the future, clearly label your DEF and diesel tanks, and ensure personnel are educated about the differences between DEF and diesel fuel nozzles to avoid mix-ups.
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Disconnect injectors and run clean fuel through the system
If you've accidentally put diesel exhaust fluid (DEF) into your diesel engine, you'll need to act fast. DEF is corrosive and harmful to several metals, including carbon steel, brass, aluminium, copper, magnesium, nickel, and zinc. It can cause severe damage to the fuel system, including line rusting, injectors sticking open and failing, and pump failure.
To disconnect the injectors and run clean fuel through the system, follow these steps:
First, locate the fuel injectors in the inlet manifold and disconnect the pipework. On a diesel engine, you may need specialist equipment as the injectors can become bonded to the engine. This equipment uses vibration to unstick the injectors.
Next, you'll need to prevent fuel from entering the injectors during cleaning by disconnecting the fuel pump. Remove a fuse or relay to do this, then start the engine and let it run until it uses up the fuel in the lines and dies, depressurizing the fuel system.
Now, carefully disconnect the electrical connectors from each injector. Use a wrench to remove any bolts or fasteners holding the fuel rail in place, then gently lift and remove the injectors, being careful not to damage them.
Attach a hose from your fuel injector cleaning kit to the fuel port on the fuel rail. The kit will bypass the vehicle's fuel system and provide a direct stream of cleaning solution to the injectors. Run the cleaning solution through the injectors for 15 to 30 minutes, depending on the level of clogging and your kit's specifications.
Once the cleaning process is complete, reattach the fuel rail and injectors to the engine, ensuring they are properly seated and secured. Reconnect the electrical connectors to each injector, then reconnect the fuel pump by replacing the previously removed fuse or relay.
Turn the ignition to the "on" position for a few seconds and then off again to re-pressurize the fuel system. Check for any leaks around the injectors and fuel rail, then start the engine and let it idle to ensure everything is functioning correctly.
This process will help remove any DEF contamination from your diesel fuel system and prevent further damage to your vehicle.
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Frequently asked questions
Do not turn on the ignition or drive the vehicle. Disconnect the injectors and run clean fuel through the system after changing the filter and removing the contaminated fuel from the tank. You may need to replace the entire fuel system, depending on the extent of the DEF contamination.
If the engine is started, the diesel and DEF mixture will be introduced into the engine, which can cause long-term consequences. DEF is corrosive and harmful to several metals, including carbon steel, brass, aluminium, copper, magnesium, nickel, and zinc.
The vehicle may hesitate or experience problems accelerating. The engine will have trouble with combustion, causing the vehicle to sputter, rev, or jolt to a start.
