Diesel fuel spoiled by poor management

[Oily Rag]

I have an Eber with a dedicated ten litre diesel tank. For the last five years, I've kept it topped up regularly, never letting it get even half empty. In addition, I've made sure to seal the O ring on the flush deck filling fitting with a bit of Vaseline each time. Water still seems to enter, though. The flush deck steel cap drips water every time I take it out. Perhaps the breather lets it in. So, I shine a bright torch onto the opaque Eber fuel tank, find the water level and then take it out with a small pump and a bit of pipe. In addition, there is a coarse filter at the tank outlet. All well for five seasons until the Eber stopped working.

I drained the tank completely and the sample on the right is the last couple of litres. As you can see, it has water on the bottom and cloudy diesel on the top. The creamy layer in the middle was a mystery until I mixed up a sample of diesel and water and dropped in a thumb-sized chunk of Vaseline. It sank through the diesel and floated on the water for a few weeks until I gave the whole thing a good shake. Then it dissolved in the diesel and made it cloudy, before settling over a couple of weeks to be the sample on the left.

The interesting thing to me is that the chunk of Vaseline is now the start of another creamy layer.

So for five years, I've been failing to fully use the fuel in the tank and put in fresh fuel in single large quantities. I've dosed with Marine 16, but have allowed Vaseline to contaminate the tank. And then I've gone for the occasional sail to mix it all up. A recipe for old, poor quality fuel.

From now, I intend to run the tank until it's almost empty, then fill with fresh diesel. At the end of the season, I'll assume that the water layer I can see has a layer of creamy Vaseline/diesel that I can't see and will just drain the lot. (In contrast to my filling it and the the engine tank up at the end of the season.). I've also installed a cheap filter bought on eBay because it has a glass casing that lets me see if the diesel has gone cloudy.

It's worth noting that the engine tank recirculates via the leak-off line as the engine runs. A dedicated Eber tank just sits there.

I've posted this as something for others to consider. Sorry it's a bit long.

Good luck!

 

[thinwater]

The creamy layer is oil/water emulsion. Very common. I very seriously doubt the tiny amount of Vaseline you put on the o-ring has anything to do with it.

 

[RichardS]

The creamy layer is oil/water emulsion. Very common. I very seriously doubt the tiny amount of Vaseline you put on the o-ring has anything to do with it.

I agree. The vaseline might actually help to stabilise the water in its emulsified state rather than it separating out but it's not the cause of the problem.

Richard

 

[penfold]

Looking at the pictures I'd say you need to drink more water.

 

[Spirit (of Glenans)]

I would recommend emptying the tank and cleaning it now, and then cleaning annually.

 

[Martin_J]

I might question whether the cap is the correct one for the deck fitting... Has just a lost cap been replaced in the past?

 

[[70521]]

Goodness me!

Are you nipping up the fuel cap?

 

[pvb]

I think it's much easier just to feed the heater from the main tank.

 

[wizard]

Ditto

 

[Oily Rag]

Thanks for all the comments. The cap is the right one and fits well. The O ring is good and fairly new.

I agree that it would be better to take from the main tank, but I'd have to cut a hole to put the fitting in. Not easy to work in a confined space.

I did think of returning the engine fuel leak-off to the Eber tank and then letting it spill into the main tank. That way, the Eber tank would always be clean. But again, more connections in a confined space..

To be frank, I posted the photos to show people what could happen over a few years. At least I kept the diesel bug away!

The one thing that puzzles me is that every time I take the (steel) filler cap off, it is cold and drips water. If it's condensation, then I'm stumped for a solution. Perhaps paint it black and get some solar heating. ?

Many thanks.