Determining fuel contamination

[Wookey]

After a bit of a saga with a load of water in the IP on my Xantia (engine)/Expert (body) last october/november (see http://www.frenchcarforum.co.uk/forum/v ... =4&t=41729" onclick="window.open(this.href);return false; ) the van has been working fine for the few trips it took, although it's mostly sat on the drive all winter. I recently went to Wales and back ( from Cambridge), which was fine until about 1 mile from home it went all coughy and spluttery with the guage still reading 1/4 of a tank. Didn't quite make it home and left it outside a mates house before bringing some fresh fuel over a couple of days later and getting it going enough to get home.

Decided that I really did need to actualy take off and drain the fuel tank like I meant to after the previous issue, but it's been too miserable for months. Did that and got some 'interesting' stuff out of the bottom of the tank. About a litre of darkish brown stuff which is immiscible with deisel and therefore is presumably mostly water, and a bit of 'mank' which floats at the interface. Also a couple of jars of 'milky' but still diesel-coloured stuff. left overlight the top 2mm or so clears, but the rest stays milky.

I want to work out what I've actually got - just water or maybe biological growth ('diesel bug'), and whether there is significant water still entrained in my fuel.

Does anyone have recommendations as to the order of tests and better/worse testing stuff? I found water-absolrbing polymer from oily bits for £8 which looks like good gear, and they have 'water detection paste' ('Kolor Kut' ) too (£7.50), althoough I think that only detects free water. They then spoil this a bit with £9.50 delivery which seems a bit steep. http://www.oilybits.com/water-removal/o ... d_436.html" onclick="window.open(this.href);return false; http://www.oilybits.com/kolor-kut-paste ... d_149.html" onclick="window.open(this.href);return false; . And I found a bio-detection kit from fox for £12 (plus 5.50 delivery): http://www.fuelcare.com/fox.htm" onclick="window.open(this.href);return false; inlcuding deleveries that is £45 which is a bit more than I wanted to pay, but such is life.

I'm not sure whether to get a biocide too to be sure (as opposed to getting the test kit and only going shpping if it says yes). There seems to be lots of those, but none cheaper than £20. Any experience of these?

I should take and post some pics of my collection of fuel samples, as it's quite interesting and in this case a pic is worth a lot of words.

[myglaren]

You could try Methylated Spirits, which is miscible with both water and diesel, to try and flush out the remaining residue.

I give no guarantees but found it worked with a Hillman Imp that got water in the petrol tank. Sloshed some of that in then added petrol to mix it up.
Won't address the biological growth unfortunately but certainly won't feed it.

If you have much river traffic near you it might pay to ask around the docks and jetties as marine fuel systems seem to be plagued with that and they will have methods of attacking it that land-bound traffic may not.
Perhaps a ships chandler if there is one.

[Xantidote]

My friend has the "diesel bug" in his boat's fuel tank. Probably picked up from some marina fuel berth where there wasn't a good turnover of diesel fuel. It's black, and eventually blocks the fuel filter. We try to keep it at bay by keeping the tank full, and using an additive when refuelling, though I suspect it's getting a little worse year by year. When you let the diesel bug debris dry out, then as best I can describe, it looks wispy and paper like, but there's nothing there when you press it between & thumb.

Your darkish brown stuff sounds like rusty water perhaps? Definitely want all water out of there - won't do your fuel pump any good. Albeit on a petrol engine, but I recall a fuel starvation problem on a boat, because water in the petrol soaked into the paper element of the fuel filter, and wouldn't allow petrol through. I know this isn't your problem, but assume you'll be changing the filter (we resolved the problem on the petrol engine by fitting a water separator)

I'd be tempted to flush the tank as best you can, and only refill with fuel you are happy with, then see how it goes. No experience of any test kits, but not sure what they'd prove to you. Maybe save their use for next time (hopefully there won't be a next time).

If you did have the diesel bug, one recomendation is to steam clean - a bit of hassle.

Now that diesel has up to 10% biodiesel in it, courtesy of the EU bureaucrats, maybe the diesel bug will become more of a problem.

Not sure if it's relevant to you, but diesel and water churned up together will mix into an emulsion, which will also block filters - not sure what colour it would be.

Good luck

[Wookey]

I did some reading and the B2-B20 biodiesel range does tend to encourage diesel bug. Pure biodiesel is OK because the water stays entrained (it is slightly hygroscopic), but at lower concentrations some free water can separate and because BD is quicker to digest than petro-diesel, the bug can grow faster.
Turns out there there are three different organisms that can cause problems, two bacteria and a fungus. This document seems to be a good summary: http://www.fuelcare.com/pdf/biodiesel.pdf" onclick="window.open(this.href);return false;

Mind you, I'm not going ot blame 'EU bereaucrats' for this bit of chemistry/biology, or the attempt (not entirely successfully) to make transport fuels less of an environmental problem. Did you know fuel consumption had reduced by 20% since 10 years ago in the UK? That's a good thing. More to do with vehicle efficiency and fuel price than diesel/BD substitution, but it all helps.

Feedback from oilybits was to clear the crap out and put in a bit of biocide to kill any more that's hanging around in the fuel system. Then change the fuel filter after a while as it'll collect all the dead bugs. Seems like sensible advice.

BTW does anyone understand how water seaparators work in real fuel systems? Water only separates when fuel is left to settle - mix it up and it gets entrained. It seems to me that there is no way it can be travelling slowly enough when being pumped through the system for water to settle out. But presumably they do in fact work...

[Old-Guy]

Water Separators (good ones that is) as used on boats and plant work on the same principle as a Dyson vacuum cleaner, but the transparent bowl does need to be checked daily and any water drained off. The problem with boat and plant fuel tanks is that they tend to be BIG and really difficult to drain completely. A big tank in a cold environment with intermittent use is prone to condensation. The nett result is a permanent puddle in the bottom of the tank that breeds diesel bugs on the fuel/water interface.

If you are anywhere near a Pirtek Service Centre, pop-in and ask them about hydrophylic materials. Their oliophylic mat has completely cleaned my cooling system of oil now that the source has been fixed by a head gasket change.