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Fuel Contamination Advice

I have recently suffered fuel contamination, presumably by water. Following research on-line I added a dose of Aquasolve to the tank which was about half full. Following the additive instructions I then topped up the tank with fresh fuel. When I re-started the engine it smoked, spluttered and died. I drained a milky white substance from the drain plug on my fuel filter so I pumped out fuel from the bottom of the tank. A large amount of a milky white 'emulsion' sank below a pink cloudy quantity of fuel in the plastic container. (photo available) How has this happened? What is the white emulsion? Advice please. Many Thanks.

Asked by: Eamonn Hallmark  | 12.38pm, Wednesday 9 March

WW says:

The white emulsion is a fuel-water mixture- very much like mayonnaise. Unfortunately, it sounds like you have a gross contamination of your fuel tank with water- and above a certain level (around 1%) an additive will not enable the fuel to be emulsified sufficiently to allow a small quantity of water through.
For gross contamination (and I am assuming this is a diesel tank) ideally there should be a drain valve at the base of the tank, to enable you to remove the water- failing this, syphoning water off from the bottom (as you have done) is the next best thing.
Some marine engineers do not like the type of fuel additive which attempts to emulsify the water into the fuel, as this can lead to it precipitating out further along the fuel system and usually cannot deal with significant contamination. Many engineers prefer additives which encourage the water to be precipitated out (so it can be drained or easily seperated by a fuel filter).
Depending on the state of the fuel, it might come to require a fuel polishing service to remove the contamination. Certainly draining water (and any emulsion) from the base of the tank is key. It is also unlikely that a basic engine fuel filter will be able to cope with the water load- at the very least you are likely to require a new filter cartridge, as the engine stopping suggests the filter has been blocked.
Ideally, you would fit a water-fuel separator inline before the main engine fuel filter. A unit like the Fuelguard units with a transparent bowl (meeting ISO 10088; required to meet the boat safety scheme standards)) which allows the majority of the water and larger contamination particles, before the engine filter gives it a final polish. The transparent bowl allows to to spot contamination and drain the bowl regularly.
You may need to consider flushing through the diesel fuel pipework to the engine- a fuel-water emulsion has a nasty habit of sticking inside the pipes, which could then lead to further filter blockages.
You may need to check that none of the contaminated fuel has left the filter (check the output of the filter in the direction of the fuel pump). If water has got through, then there is a possibility that the injectors or pumps might be at risk of damage.
If you want to email any pictures or require more discussion, please feel free to email me at mark.langley@waterwaysworld.com

Mark Langley  | 1.31PM, Wednesday 9 March

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