Diesel Bug - modification to fuel line

[Craig]

We have just had our second Diesel Bug attack in 2 years. Both attacks occurred while motoring in rough conditions with our tank less than 1/2 full and just after dozing the tank with an enzyme.

In both cases, the lump of Gunk did not reach the filter. In both cases the engine stopped because the gunk was caught in the fuel off/on switch.

The aperture of this valve is less than the fuel line. A piece of gunk the size of a raisin blocked the valve to such an extent it had to be blown out with compressed air.  The fuel filter, in both cases had some Gunk but was not blocked to cause any drop in fuel flow.

We have now installed an inline fuel strainer before the off/on valve.

This strainer collects all the lumpy gunk that could block the off/on switch but allows small stuff through to the primary filter.

After installing the strainer a large blob of gunk was caught in the strainer. After 9 hours of motoring the enzyme in the fuel seems to have "dissolved" this gunk. The primary filter has some discolourisation but is clear. The fuel has been slightly discoloured by the gunk in suspension but the engine is performing well.

The Bavaria agent in Malta, as well as the Volvo dealer there have never had a problem with Diesel bug blocking fuel lines or filters after installing the strainer even though the strainer collects large blobs of gunk.

They have never seen a Bavaria stop because of gunk in filters and believe that all instances they come across the gunk is caught in the on/off valve.

I strongly recommend that everyone install a strainer ( 4 euro cost in Europe) in the fuel line before the off/on switch.

I also believe that the enzyme treatment actually loosened up the gunk in the tank causing the blockages we have had, but also later "dissolved" the gunk held in the strainer.

I have photos if anyone is interested and would appreciate feedback as I am considering writing an article on this issue.

This issue also affects other boats and is partly bought about by different regulations regarding the location of fuel on/off switches and the materials and fittings to be used in the construction of fuel lines. I am aware that the plastic see-through strainer I have installed is not compliant with the fire safety requirements but my risk analysis is that this is a minor threat compared to entering a harbor in adverse conditions with no engine.

Craig Hardy
s/v "Shirley Valentine"
2009 Bavaria 38
The Mediterranean   

[Odysseus]

Put some photos up so we can see your installation, interesting artical, its a big issue here in France since and because of the bio fuel additions started.
Odysseus
Bav 38

[Aquila]

Craig, thanks for the article.  I was once told that its best to use diesel bug additives from the very beginning of a boat life otherwise it will just loosen up the bug and cause a blockage like you described, because of this I have never put any additives in the fuel. I think your assessment is correct.  I must admit to always keeping my tank full to minimise the chance of the bug but again only time will tell.  thanks

[dawntreader]

Craig, thanks for the article.  I was once told that its best to use diesel bug additives from the very beginning of a boat life otherwise it will just loosen up the bug and cause a blockage like you described, because of this I have never put any additives in the fuel. I think your assessment is correct.  I must admit to always keeping my tank full to minimise the chance of the bug but again only time will tell.  thanks

I'm sure I read in PBO recently that the percentage of bio-fuel content has been/will be increased:

Much of the new fuel will contain a proportion of FAME ? Fatty Acid Methyl Ester. This is a bio-fuel obtained from renewable sources intended to reduce consumption of the world?s limited oil supply. It can, however, have a seriously detrimental effect on some
marine engines. It is known to make worse the problems of ?bugs? in tanks causing blocked filters, break-down to acids leading to engine
equipment damage and leakage from fuel component seals. The storage life of fuel with FAME is also much reduced and it may necessitate
costly tank emptying over winter and even disposal of contents for many yachts and motor vessels.


Read more at http://www.pbo.co.uk/news/yachtsmen-concerned-over-introduction-of-ultra-low-sulphur-diesel-5686#sYI6qkgvjOvHQ6Pp.99

[MarkTheBike]

Just had a quick squint at the link - looks like it's from 2011 originally. Has there been an escalation since then?

[dawntreader]

Just had a quick squint at the link - looks like it's from 2011 originally. Has there been an escalation since then?

Yes, I read very recently the % content of bio-fuel in diesel is set to increase - it was in PBO but I can't find the article. However, the conclusion of the article suggested a re-think of the advice about keeping the tank full over Winter, instead to empty it at the end of season. Sorry I can't be more specific but will keep looking and post when I find it.
Jim

[BillGiles]

We had the diesel bug problem off Beachy Head and had to be towed in. The lifeboatman said that there had been a lot of reports of this same problem by people who had refuelled in France. It took a lot to clear the system of the horrid gunk and as was said above there was a big chunk of it in the on/off fuel cock. I think the idea of a strainer is a good idea. They are very cheap at £1.99 from Screwfix but one needs to put them between the tank and the cock but then you need another on/off between the tank and the filter!

(http://www.screwfix.com/p/ring-in-line-diesel-fuel-filter-mm/12467?kpid=12467&cm_mmc=Google-_-Product%20Listing%20Ads-_-Sales%20Tracking-_-sales%20tracking%20url&kpid=12467&cm_mmc=Google-_-Shopping%20-%20Car%20and%20Van-_-Shopping%20-%20Car%20and%20Van&gclid=CNW0-P_LmMUCFUHItAod_VkAnQ#product_additional_details_container)

[Aquila]

Thanks for the link, now I am getting worried about the bug.  Just one thought, if you have a diesel heater on board, supplied from your main tank, can you use the fuel filter supplied for your heater to occasionally observe how clean your diesel is.  Surely any discolouration of your heater fuel filter will suggest further investigation.  I run my heater each month for half and hour as a matter of good practice so it does get regular use.  Just an idea.

[blue-max]

Following on from this issue I wanted to inspect my tanks - located under the aft berth -ocean 47 - and was surprised there was no inspection hatch or way to clean the tanks. Has anyone fitted hatches or found a way to clean the tank?

[Odysseus]

I put this on the forum some time ago, just a method I use to check  my fuel condition. It works.

Odysseus
Bav 38

[BillGiles]

When we had the diesel bug I removed the supply pipe which is only held in place by a grommet. I then used the gadget we use to suck the engine oil out from the dipstick hole when doing an oil change. Just used the thin pipe as a vacuum cleaner and sucked around the lowest part of the tank. Got some gunky stuff out. A good dose of bug killer and all has been OK since.

I had an idea to put a connection between the coarse and fine fuel filter with an outboard typ connection on it. If the supply gets stopped for any reason then I would have an outboard type hose and bulb to draw fresh fuel from our gerry can of fresh fuel straight into the fine filter line. Anyone tried it?