I?ve being storing some diesel in an outdoor storage tank. Unfortunately the fuel has become contaminated with water. Would it be sufficient to carefully syphon off the diesel from the top of the tank after the water has settled on the bottom.
Would any water residue, however small, remain in this recovered diesel?
Would it be enough to damage an engine/fuel pump of a VW TDI ?
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I can answer this from experience. The water separates from the diesel and sinks to the bottom. You can safely use the diesel remaining. If possible, the best way is to let the fuel "leak" out from the bottom of the tank first, but if you have no access to the bottom, then syphon off most of it (or pour carefully if a small tank) and then put the last bit into a separate container and leave overnight. This will be enough to allow the two liquids to separate.
Anyone with a central heating tank should do this once a year. You will be amazed at the amount of water you get out of a fuel tank. 2 milk bottles full from a 500 gallon tank per year is my experience.
In the event of a cock up, it will cause no damage, but you will have to bleed the system which is a pain but nothing more.
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Oil tanks should always be installed with a slope towards the drain off plug at the opposite end to the fuel outlet pipe/tap. Never level.
As Richard has said, sludge and water collect at the low point and can be drained by removing the screwed in plug. Care needed of course not to lose the oil!
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Thank you both for your valuable contributions.
But my main concern would any moisture remain after allowing gravity to separate the water out and if so, would it be harmful in a high pressure direct injection engine?
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My experience of boat and civil engineering plant is that if you keep your water trap drained off you won't have any problems.
But I was taught that if you should allow water to reach the injectors they will be damaged because of the difference in viscosities.
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With canal narrowboats, I found it easier to use a Colley pump to drain off the water from the bottom, carrying on till only pure fuel passed.
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The bulk storage of heavy and light fuel oils at the site I work at (ca 1 million litres) naturally loses the water present in them to the bottom of tanks which is then automatically purged every week or so until fuel is present.
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Same here with the tractor, drain tap at the bottom of the tank. Draw off a little to test before each days use.
David
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Basically YES
The Golf TDI has a fairly basic filter which itself will not be enough to protect the high pressure injection system from the water. It is amazing how relatively short periods of moisture exposure will cause oxidation even within a clossed fuel system, secondly as someone else mentioned, the injectors will suffer pitting as water fuel emulsion is forced through them at 1300 - 2000 bar.
After draining the free water from the tank, the background contamination will be down to a few hundred PPM of water in the fuel, to bring the level down to bellow 100 PPM you would need either a water absorbing filter, or a good quality water separator (2 micron), These are available from Racor, Fleetguard or Mann&Hummel.
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Thanks Adam! you've confirmed my suspicions that water/moisture may still be present.
I'll check out your filter advice.
Is this a piece of very fine gauze to put in a funnel or is it something more elaborate?
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These are normally a paper with a chemical hydaphobic coating which repels the water in the same way as goretex would on a coat. Alternatively some work as absorbers, soaking up the water moisture out of the fuel.
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Thanks yet again.
Using your excellent advice I turned up the following on the internet after a search.
"FLUSH DRAIN SAMPLER CUP FUEL/WATER SEPARATOR FUNNEL
8" bowl dia. www.wicksaircraft.com part# FSF-4 $25.50
Replacement element 8" bowl dia. www.wicksaircraft.com part# FSF-5 $9.75
Utilizes a special thermoplastic-coated stainless steel base with a high-flow hydrophobic,
mesh separator membrane that has an affinity for petroleum but repels water. The element can be
removed easily, cleaned with a solvent and a soft non-scratch brush low air pressure, steam or
approved liquid cleaners. Funnel can be used for fast checking of potential contaminates, passes fuel,
collects water and solids. Replacement elements available when required."
I wonder if this funnel or something similar is available in the UK ?
On most of the UK sites the filter was an elaborate in-line set up using a cartridge.
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Bye the way I checked with the wicksaircraft website in USA and this product is not availble at present.
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If you give me an address I'll send you a suitable filter FOC, and you can see if it takes any water out.
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Great news, will try and contact you direct.
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