Diesel bug cause effect and cure

The mix of bio diesel with natural diesel has created a fuel that actually provides nutrition to micro organisms. Diesel bug cause effect and cure.

Having previously covered some of the dangerous mechanical effects of water ingress into the diesel used by any type of vehicle that uses diesel as a fuel, I have to add a further danger brought about by what is universally known as diesel bug.

Diesel bug is in fact, a living microbial organism that is bacterial in nature, but can also be fungal too. It is capable of reproducing itself very rapidly and like all living things it eats, excretes, reproduces and dies. It is the dying and excreting that causes the problem we experience when the slime like residue of decomposition blocks our filters. If the bug residue gets passed our filters it can block, or damage fuel injectors and the injector pump itself, as well as the feed pipes etc.

The diesel bug needs water to survive and breed and we certainly wouldn’t dream of knowingly pour water into a fuel tank, so it begs the question –

Where does the water come from

If you are quite certain that water cannot get into your fuel tank through a faulty fuel filler cap or similar, it can only be either contaminated fuel from the supplier, or condensation. Let me explain about the former first, not knowingly buying contaminated fuel.

Underground fuel storage

For the most part, here in the UK, most road fuel purchased is from service stations that have a very high turnover in fuel that is stored underground. The storage tanks are huge, and being below the ground, have a generally stable temperature. They empty and refill very regularly. They are refilled by tankers that have received the fuel they carry from vast storage vessels that are designed to properly store the fuel that they contain. Very little chance of contamination from this source.

Overground fuel storage.

On the other hand, not all fuel is stored underground at a stable temperature. We live full time on a boat and whenever we fill the boat with fuel, we invariably have it metered into our tank through a standard pump that counts the litres and gives us the price. However! The fuel tank that actually stores the fuel we’re buying is in an overground tank. The temperature in this tank goes up and down like a yo-yo! This is where you are going to find condensation, and that condensation is going to end up in your fuel tank!

How does the fuel bug survive and where does it live?

Diesel bug has always been around but was far less successful before the blending of standard diesel with 7% FAME biodiesel. Fame stands for ‘fatty acid methyl esters’. This biodiesel is produced from plant oils and old oil from fish and chip shops and restaurants. The problem is that this oil will actually absorb water.

Condensation in your fuel tank will, over time, build up. As you may know, diesel floats on water and the diesel bug lives right there, where the water meets the diesel. It lives there because of the nutrients supplied by that 7% blending of bio-oil. Additionally, as condensation forms on the walls of your fuel tank, the bug can colonise that space too!

So, what can be done? Diesel bug the cause effect and cure.

In severe circumstances, it may be necessary for you to get your fuel tank cleaned professionally. This is known as fuel polishing. However, this is not all. I’ll detail what may be required. You may be able to avoid this if the contamination is not too bad.

• • Clean the fuel tank if possible. This will remove any detritus and water. Whether you reuse the original fuel, or replace it with new, treat the fuel with Marine 16 or other branded fuel bug treatment using the shock amount as advised by manufacturer. As the treated fuel goes through the system it should destroy any lingering bug pollution.
• • Install a water separator / trap between the fuel tank and the fuel pump. If you find that there is already a filter buried in that fuel line, I’d be tempted to bypass or remove it. That kind of filter is rarely seen so easily forgotten. On my own boat I diverted to fuel pipe from the tank up into the wheelhouse and legally fitted a glass bowled water trap and a pair of CAV fuel filters. I then connected from the filters to the diesel lift pump. I can see any problem and easily clean the trap and change the filters if required. There is a link at the bottom of this article to the first half of this article that has a picture of my own water trap.
• • Remove all fuel filters and replace with new
• • Thoroughly bleed the system and start the engine.
• • Run the engine at a fast tickover for about 30 minutes while checking the contents of the water trap. If you have not fitted a visible water trap, I would definitely change the filters after a couple of hours running. If you have a glass bowled water trap, keep an eye on it. As it is, as the treatment works, there is going to be slimy detritus to remove. You may well have to change filters more than once.

I use Marine 16 Diesel Bug Cleaner and have first hand knowledge of how good it actually is. It’s also used by the RNLI which says a lot I think. Maintenance dose is 100ml per 2,000 litres, full scale assault on diesel bug is 100ml to 1000 litres diesel. It’s a good idea to mix the Marine 16 with 5 litres of diesel first rather than just pouring it into the tank.
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Can I take precautions?

Yes. Follow the instructions closely and use the ‘prevention’ quantity of bug treatment every time you add fuel. Either dilute the treatment in diesel or add the treatment followed immediately by diesel. If you are adding a large amount of fuel, add half the treatment at the beginning and the rest before the last quarter of the fuel. Additionally, condensation can’t occur in a full fuel tank, so fill the tank before leaving it for some time.

Further reading.

I hope you found Diesel bug cause effect and cure, useful. If you want to read about other water related diesel problems, and an image of my own water trap take a look at the first half of the article. Water in Diesel

Wikipedia has more information HERE about diesel bug and fuel cleaning (polishing)