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We get many requests about the the uncertain condition of fuel in a boat or yard tank. How can you tell if there might be an issue? Is the fuel old? What symptoms might there be?

  • Engine revs varying, as if the engine is hunting for fuel

  • The vacuum gauge needle is flickering (indicating changes in vacuum pressure)

  • Engine cuts out.

  • Engine is hard to start

  • Excessive exhaust smoke

  • Fuel smells rancid.

  • Fuel is dark in colour / milky

Firstly, check the filters. What is the condition of them? can you see anything physical? What are you looking for?

That would depend on the type of filter. A filter where you cannot see a bowl at the bottom could be a Donaldson type. Carefully unscrew the filter making sure you hold a bucket or such like underneath to catch an fuel spillage. Once loose, tip the entire contents into a clear container. Look at the sample from the side.

What does the fuel look like? clear? amber? dark? black?Milky? Are there bits floating in it? specs of brown?

This could be sludge. What is sludge? basically this is the clumping of bacterial growth (likely Cladosporium Resinae) in sessile form, held together by polysaccharides (sugars). As such, it manifests as a dark slimy organic matter that builds up in the bottom of your tank, and eventually gets sucked into the fuel intake leading to the filter becoming clogged.

Having explained that, not all dark slimy matter in the bottom of your tank is necessarily Sludge as such. It could be an agglomeration of asphaltenes. This is where diesel slowly starts to revert back to it's original crude form due to the constant heating and cooling process it (the fuel) goes through.

Any water will likely manifest as small bubbles or a layer right at the bottom.

The other type of filter will be a Racor or such like, with a clear sight bowl at the bottom. If the plastic of the bowl is discoloured you may wish to consider replacing this in the interests of better detection.

Anyway, any bits floating in the bottom? Any water in the bottom?

If any of these symptoms are present, It is possible / likely there will be contamination of some sort.

In extreme cases you may wish for a sample to be drawn and sent for analysis. This way, you will be sure, and you will get advice on the correct course of action.

Don't forget, you are working with expensive equipment and for boats, safety at sea is not something you dice with. Better to be sure and employ a maintenance dose of a treatment such as FuelRight. Water is pushed to the bottom and NOT drawn to the injectors. Any sludge and Biofilm is slowly dissolved away. Given the minimal cost, why wouldn't you?

For further advice, contact Fuel360 on 0800 777 551 and we will be able to help you with a safe and economical resolution, or email us now

Remember, not all treatments are equal. Cheap does not mean better for your equipment.

Read the other posting on this website under Fuel Integrity.

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