Small Amount of DEF in Diesel Tank (How to Get It Out)


Operators and truck owners must ensure that diesel fuel is not accumulated in their diesel tanks, causing diesel fuel system contamination.

One simple error in judgment can send a vehicle to the scrapyard. DEF is a cleaner and more efficient way to keep the environment clean. If DEF is misused, operators could face a severe problem. DEF is a combination of urea and water. Diesel fuel and water-based DEF are different in density and cannot be mixed.

DEF contamination is when there is little to no DEF left in the diesel tank. It would be best if you did not drive or start the engine. Change your fuel filters immediately and flush your entire fuel system. Depending on how long the fluid has been there, you may need to replace or repair parts, especially after ignition.

Pour the DEF into a tank to inject the exhaust pipe.

What is DEF?

DEF stands for diesel exhaust fluid. It’s a relatively new term if you have been driving diesel engines for years but don’t know what it is. According to the Environmental Protection Agency, all-new diesel engines must emit less nitrous dioxide from 2010 onwards. Selective catalytic reduction is one way that manufacturers can meet this standard.

Exhaust gases pass through a filter that traps soot and ash. After the exhaust gas passes through the filter, it is sprayed in DEF (67.5% purified and 32.5% urea) and then into the catalytic convertor. When cleaning the pollutants further, the catalytic converter uses a variety of metallics before the exhaust leaves the tailpipe. The diesel vehicle runs cleaner and burns more fuel, which results in better fuel economy.

Consequences for a Small Amount of DEF in the Diesel Fuel Tank

There are many ways DEF can enter a diesel fuel tank

Operators assume that a small DEF amount will cause engine damage because it is so dispersed in the fuel leading to costly and risky mistakes. Change fuel filters immediately, depending on the circumstances and advice from diesel mechanics.

Keep changing filters until all diesel fuel is gone from the tank. If the operator notices any abnormalities in the engine’s behavior or performance, take it to a trusted mechanic.

You should immediately realize your error if you have poured DEF into your fuel tank, and you will need to repair or replace parts due to the accumulated fluid.

Your engine will stop working, and you will need to replace or repair parts before it can start again. This is a situation that will require you to take the vehicle to a professional to assess the damage and make any necessary repairs.

What Happens If The Engine Is Started?

Fuel delivery uses a gravity-fed system. DEF is 67.5% water and will build up at the bottom fuel tank. The engine may not start if there is too much DEF in your fuel system.

The engine will start with a smaller DEF, but the operator will experience severe performance problems. The vehicle is slowing down or having difficulty accelerating and the engine is experiencing issues with combustion.

The vehicle will sputter, rev, or jolt to a halt when water-based DEF is sucked into injectors. Pure diesel fuel is used to cause sudden acceleration.

After starting, the diesel engine will stall on the highway. The machine will not start if there isn’t enough DEF in its fuel system. Water-based DEF can hinder combustion.

The amount of DEF allowed in the fuel system can directly cause damage to diesel engines. A teaspoon may suffice to make the system safe.

Anything more than that, and your engine could be in serious trouble. DEF, which is denser than diesel fuel, will settle to the bottom of the fuel tank. DEF can rust the tank and further contaminate the system.

Diesel engines require precise fuel injection into the combustion chamber. Diesel injectors have a higher fuel density specification due to the increased pressures. DEF contamination can cause injector failure by putting more strain on them. To a certain extent, filters will remove contaminants.

Fuel lubricates a fuel pump. This operation will be hampered by DEF contamination. When the key is turned, DEF is forced into the fuel lines.

Defective gaskets in the fueling system could cause DEF to leak into your oil sump, leading to DEF and oil leaking into the oil sump, which will cause sludge that can affect the engine’s lubrication.

A combination of these circumstances or one individual case can cause engine seizures.

How do you get DEF out of a Diesel Tank?

DEF is the most harmful to diesel fuel systems. The fix for DEF contamination could be as simple as dropping the tank or flushing the fuel lines.

Before you turn the key, tow your vehicle to a competent mechanic. DEF is corrosive, allowing the material to sit in fuel systems will cause further contamination.

While some fuel additives might work, it is not always possible to use them all. You might also consider adding fuel driers. Many local and national companies are experts in cleaning fuel tanks contaminated by DEF.

The cleaning company may deliver a mobile unit depending on the circumstances. If they feel the problem can be resolved on-site, they will do so. If DEF contamination is severe, the vehicle will be towable back to the shop for cleaning.

How to Fix a Diesel Exhaust Fluid Contaminated Fuel Systems

There will be different cleaning stages for each pickup and heavy-duty truck. Because of the open cab design, access to the 18-wheeler’s fuel system is more manageable. Heavy-duty trucks and pickups may need to lift the body off the frame to gain full access.

Remove defective fuel from the primary fuel tank and injectors. It is necessary to replace fuel coolers, pumps, switching valves, and other components. These are areas where DEF crystals can hide. You can remove plastic tanks and intakes, clean them thoroughly, and reuse them.

Technicians will dismantle the entire fuel system. Some engines may have aluminum fuel rails and manifolds that need removal because DEF corrodes aluminum.

Dispose of feed lines, clean, and replace some injectors. Some argue that replacing a fuel system with dirty injectors is not worthwhile. It is possible but unacceptable to salvage a fuel system that has been contaminated by just water and its parts.

The cost of cleaning a DEF-contaminated fuel tank can vary depending on the situation.

These factors include the amount of DEF in the fuel system, the vehicle’s location, and the type of vehicle. It is imperative to identify any heavy DEF contamination car’s year, make, and model.

Older models don’t have the same sophistication and features as modern diesel engines. How long has DEF been in service?

Dealership service departments can charge between $12,000 and $20,000 to clean a DEF-contaminated vehicle. In some cases, the cost of cleaning up the car might be more than it is worth. Dropping the fuel tank would be a better option than a thorough cleaning.

For this level of clean-up, mechanics charge between $2,000 and $5,000.

How to Avoid Contaminating Your Diesel Tank

Prevention is better than any other option. There are several ways to ensure you don’t accidentally put DEF in your fuel tank. DEF fillers usually have blue caps that are smaller than regular fuel tank caps.

Manufacturers may place the DEF filler underneath the hood to reduce the risk of making a mistake as the DEF cap isn’t located next to the fuel cap. You might add DEF to your fuel tank if you aren’t familiar with the details.

Blue caps are used to fill DEF tanks. They are usually smaller than the fuel tank cap.

Some manufacturers place DEF fillers next to the fuel tank. They are smaller and more visible than the fuel filler, making it easier to distinguish between them. DEF is a crucial automotive advancement. It reduces diesel emissions and improves fuel economy. Make sure you keep it in the right tank.

Key Takeaways

Pay attention to avoid small amounts of DEF in your diesel tank.


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