Sunday, 6 October 2013

Diesel bug/fuel contamination

We have been having an intermittent fuel problem for the last two months.

 Before doing the Thames Tideway I had replaced the main fuel filter as well as the fuel pump filter, this was done at least 3 months ahead of schedule but we didn't want any problems on the tidal Thames.

As you know, we survived the trip but it didn't go without a hitch. We started out from Limehouse using between 1600-1800 rpm nothing unusual there but about 2 hrs into the journey Richard on NB Indigo Dream called for an increase in speed so we pushed the rpm up to 2000+ then our troubles started, after about 2 minutes we started to loose power, throttle was retarded and power was restored, again pushed our rpm to 2000+, again loss of power again the throttle was retarded and power was restored so the remainder of the trip was done at 1800 rpm. Investigation of all the fuel system, Wasp filter, Main fuel and pump filter revealed no problems. Stumped.

Two weeks ago, when we had our friends Brian and Rosie aboard we had a similar problem whilst winding below Lechlade, but this time the engine almost gave up and stalled, having knocked it out of gear and gently teasing the throttle I managed to keep her running but only just. Investigated the fuel system again, and nothing found. I was beginning to wonder whether I had a problem with the injectors.

Tuesday evening I was reading, well scanning the new Towpath Talk where I saw an advertisement for a company called MLS Ltd who were offering a product which could possibly solve my problem, I investigated their Website and found out that they were operating out of Oxford. A quick phone call and two days later Ben below came out to MR at Thrupp and carried out a fuel condition test, free of charge.

I was knocked sideways, above is a sample taken from the bottom of MR's tank and as you can see 25% of the sample is water containing rust and contamination.

Once the water was separated from the sample the diesel was tested, the sample contained 1.9% biodiesel and 2081ppm of contaminants.
FP100 Purifiner
So, yes I bought the above, an FP100 Purifiner at a cost of £208+ VAT.
FP100 installed on MR
"When the fuel enters the unit the baffles in the system immediately induce a swirling action, which causes water and solid contaminants to separate out of the fuel. The contaminants sink to the base of the unit where they are retained – the contaminants are simply drained and disposed of when the system is full. "
Now only time will tell, however, in the meantime MLS Ltd also have a portable fuel cleaning system which can be hired at £30 a day which I shall probably take advantage of.


  1. That looks like a smart bit of kit, especially as it doesn't need any aditional filters too, hope it cures your contamination problems.

    Can I suggest that you start Jill on 3 wheetabix/day as she'll need the energy when towing MR with her kayak if you break down! LOL

    1. Please no Kevin; I hate Wheetabix. How about 3 pints of Doombar per day? That'll keep my towing strength up!

  2. Hi G & J

    You didn't say if you can now get to 2000rpm, or have you not had the chance to try. Being under load is different to running out of gear of course.

    Why would you need to do your fuel now with their hire equipment, Surely this bit of kit will do it on the fly?

    Do you have a bottom drain on your tank/s to drop the water and crud out?

    Did they do a sample of fuel after the fitment?


    1. Hi Kev and Debs,

      Not yet done any cruising but did run her up to 2400 in gear tied to bank and she ran as sweet as a nut.
      Good second question, just thought that I could polish the fuel bankside and know that I was starting again from as clean as possible and then I could monitor any further water ingress!
      No bottom drain on this girl, just used a vacuum to suck as much water crud from the bottom of the tank, took out aprox 2.5lts.
      I have now run the engine for 2 hrs since and have done a check from bottom of purifiner and all is well.

      What dates are you looking to move Avalon to continent? we are now planning on middle of April.

  3. I had this problem recurrently on 'Poppy'. I was recommended to try a fuel additive called 'Marine16'. It's widely used on the Broads - and I've had no problems since.

    Graham Trim

    1. Hi Graham,

      We have been using Fuel Set and Marine 16 for the last couple of years, the problem is water ingress and crud/rust inside the tank no sign of Diesel bug.
      Hope you and yours all well?

  4. Hi G & J

    Going back many years (about 30), I remember a charter fishing boat skipper who had the same problem with water in his diesel tank, it was reckoned then to be condensation forming inside the metal tank due to the day/night temperature difference combined with the time of year (autumn). I can see the logic of this reasoning cos' if you leave a container of liquid outside overnight after it has heated up during the day there will be condensation on the outside of the container, so therefore logic says there may also be condensation forming inside the tank if it is vented to the outside air?, what if any relevence this may have in your situation I havn't a clue, and what the skipper did to cure it again I have no idea, but I thought I would put my two pennyworth into the discussion as this problem seems to the best of my knowledge restricted to boats and appears not to affect road going vehicles, why??

    Hope your new device cures the problem

    Beardy Chas

    1. Hi Chas,
      You have more than likely hit the nail on the head, bearing in mind that the fuel tank has three temperatures working on it, outside air temp, outside water temp and inside engine room temp, plus now that diesel has a Bio additive are all contributing factors. We have today had a run down to the Thames and I have had a play throughout the RPM range and this new purifier seems to have solved the problem, keeping my fingers crossed.

  5. How much crap have you drained from the filter since you have had it Graham?