Dirty fuel problems

Marco Antonello — 25 June 2012

DO YOU EVER think about the fuel you are putting in your tank? Beyond worrying about how much it costs and which grade of fuel to buy, probably not. But you should. A bad batch of fuel can wreak havoc on both diesel and petrol engines. So let's have a closer look the how, where and why of fuel contamination.

Fuel quality in Australia is generally not as good as the rest of the world and the main contaminants are water, algae and sediment from the bottom of the tanks at the service station.

Contamination is a consequence of poor management and unfortunately there isn't much we can do to prevent us from filling up our next tank with contaminated fuel. In every litre of fuel there is always a nominal amount of water; the Australian fuel standard determination is 0.05% by volume. This amount of water is said not to impact fuel system operation and makes its way into the fuel via condensation in the tank and by accidental ingress when tanks are filled.

Air and water borne spores can also contaminate fuel. Different types of spores require different conditions to germinate and they will only germinate in the right conditions. The spores settle on the surface of the fuel where they remain dormant. Movement of the tank washes condensation off the sides of the tank, mixing spores into the fuel in the process. Dissolved oxygen in the water acts as a trigger for germination and heat accelerates the process. In warmer climates such as the outback, more rapid spore growth inexperienced because of the higher temperature.

Another cause of contaminated fuel is sediment on the bottom of fuel tanks. Suction from underground storage tanks to the dispenser is via a tube approximately 50mm from the bottom of the tank. This 50mm allows condensation, ground water ingress and flash rust to accumulate. In the meantime tankers filling the tank at a rate of 1000L/minute via a 100mm drop tube will be agitating and emulsifying tank bottom debris. So, when the tank is filled by the petrol tanker, contaminants mix with the fuel being pumped into your tank.

Diesel engines are especially susceptible the contaminated fuel because the pumps and injectors have only very fine tolerances.Petrol engines can also be affected by dirty fuel, which can cause loss of power and detonation (also known as pinging), and can clog up injectors. Along with contamination can come some very expensive repair bills.

If you are a victim of contaminated fuel, you will experience rough running, poor performance and increased fuel consumption.Unfortunately, if these symptoms start to show the damage might have already been done. If you are driving a petrol or early diesel(pre-2000), hopefully all you will need to do is flush the fuel system - which should include the diesel pump being drained, fuel filter replaced and a new tank of clean fuel. Newer common rail diesel engines aren't as lucky. If spores grow into algae the fine tolerances in both the pump and injectors mean these parts of the fuel system will clog and cause up to $15,000 in repairs that aren't covered by a new car warranty.

There are some fuel treatment products on the market, mainly for diesel engines - that help prevent the growth of algae and bacteria during fuel storage and also prevent gum build up. A few brands available are Chemtech Diesel Power, Fuel Doctors Australia, and Wynns Spitfire Diesel Treatment. These products will help clean your fuel system but are only preventative and will not actually remove algae.

Another preventive step is to install an aftermarket water trap after the original fuel filter. This will give you a glass fuel bowl and another point in the system that water can be trapped.

Dealing with fuel contamination is an exercise in prevention,because if our vehicles are showing signs of having contaminated fuel on board it is usually too late. Thousands of dollars worth of damage can be done without you even knowing - so prevention is the key.

Using a fuel treatment of some sort can help prevent air or waterborne spores from growing into algae in our tanks and also clean our fuel system as we drive. But before you go out and buy one it is best you speak with your mechanic first.

Being careful where we buy our fuel is another great way of preventing contamination; this can be easy when you're filling up at the same service station every week, but this is often impossible when on the road.

Source: Camper Trailer Australia #44, Sep 2011


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