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How to Recognize and Prevent a Diesel Bug Contamination in Your Engine

How to Recognize and Prevent a Diesel Bug Contamination in Your Engine

Diesel bug has always been a major issue for boat owners, especially in recent years. It develops when microbial bacteria, algae, and mold contaminate the fuel tank. They use water and other nutrients to grow into a slimy biofilm that floats on the fuel and spreads across the fuel systems. 

The microorganisms thrive in specific temperatures, around 86 degrees Fahrenheit. There are over 100 types of this bacteria, and some of them are even airborne. The water in a fuel tank is fertile ground for this menace to grow. Some breeds can grow from a fraction of a gram to more than 22lbs in a day. Others grow slower but can create problems nonetheless, as they release byproducts such as hydrogen sulfide.

Biodiesel is quickly becoming the standard in the marine industry, and with that, the risk of diesel bug contamination increases. The higher the concentration of the biofuel the harder the outdated filtration systems can separate the fuel from the water. And with more water in the fuel, the diesel bug finds its home.

How to recognize it?

The contaminated fuel emits an unpleasant odor reminiscent of rotten eggs. A visual inspection of the fuel tank will reveal the bug in the form of sludge or slime. 

The bacterial life is present in fuel and usually invisible to the naked eye. In this state, it can pass through any filter type. As previously mentioned, the bug grows rapidly and by the time you are able to spot it the infestation might grow to dangerous proportions. 

The first sign that your fuel might be contaminated is that your engine will stop. Other common symptoms are decreased response times, excessive smoke, and poor starts. Diesel bug can prevent injectors from operating properly and deliver unbalanced power outputs.

How dangerous is it?

The waste this menace creates can cause a blockage in the filters. A diesel bug can even wreck serious havoc in your engine, especially if it reaches the injectors or the fuel pump. In some cases, the contaminated components have to be replaced completely. 

These microbes can degrade protective layers of paint, metal or rubber and can ruin the corrosion inhibitors. The contaminated fuel is unreliable and using it can lead to decreased efficiency at best and complete system failure at worst.

The acids these bugs produce can corrode diesel pumps, tanks, and injectors. Even if the contamination is not that severe, you will still experience poor fuel economy, frequent filter blockages, shortened maintenance intervals and overall poor performance and an increase in costs. 

There are different types of diesel bugs that can lead to more costly repairs. One of these is a fungus called Cladosporium Resinae. Once it infects your fuel supply it can cause serious issues to the emergency power units. When you’re not using your vessel it can grow and lead to disaster in case of an emergency once you are out in the open sea.

What Can You Do?

If your boat uses less than 15 gallons of fuel, the best thing to do is to drain the fuel at the end of the season and clean the tanks, then refuel in the spring rather than letting the fuel sit hibernate with the boat. Prevention goes a long way in fighting a fuel infection. You should properly store the fuel and keep it in cool and dry places to prevent the bug from developing.

If the contamination has already spread you might be tempted to use biocides, but be extra careful when doing so. These chemicals can be dangerous and need to be handled properly. Even those labeled eco-friendly may harm the environment if improperly disposed of. 

Additionally, using biocides can cause even more issues, as the sludge from the dead cells can pile up at the bottom of the tank. The sludge can make its way to the fuel system and cause clogs. Finally, biocides might prove ineffective after a while as the microbes develop an immunity to them. 

If the contamination is severe, the best thing to do would be to have a ship repair expert examine your fuel system and see how severe the infection is. Not addressing the issue may result in costly repairs as key components of the system are systemically damaged.

Ship Repair San Diego

PCE has over 40 years of experience in ship repair, serving San Diego and the surrounding areas. If you suspect your fuel supply has been contaminated and your engine or other crucial parts of the boat are not performing as they are supposed to as a result, our mechanics will conduct a thorough inspection of your boat and suggest the best possible course of action.
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1620 Rigel Street
San Diego, CA 92113
Phone: (619) 235-0961
Fax: (619) 233-5096 
Diesel & Motor Division
3376 Main Street
San Diego, CA 92113
Phone: (619) 235-0961
Fax: (619) 687-0038 
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Aiea, HI 96701-3281
Phone: (808) 486-6600
Fax: (808) 845-1652 
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Everett, WA 98201-1300
Phone: (425) 257-9065
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