diesel bug?

[robert anthony]

Bit of help needed, engine has just packed up. Sounded like fuel starvation as it went. Changed the fuel filter but still wouldn't start. I got it running again using a jerry can of diesel as a back up tank so looks like my fuel line is blocked. I noticed the black/green slime on the old fuel filter. Have I got the bug?

[churchward]

I would say so yes. The deposit on the filter looks like it and from your description you are seeing classic symptoms.

 

Get some fuel treatment biocide like Marine16. You may need to take the fuel lines off and blow the blockages out and once the biocide has done its job you will probably need to change the fuel filter(s) again.

 

It will all run fine once you have got this done.

 

Marine16 also do a bug test kit but although a reasonable price about £12 I would just go straight for treatment.

Edited October 24, 2015 by churchward

[mango]

It's important to clean out the tank as best you can otherwise the bug (which grows at the fuel/water interface) could find its way into the filters. A biocide ore emulsifier won't get rid of any bug that is already present.

[Midnight]

I've been using marine 16 for years but I still got the bug. I changed both filters twice a year for two years syphoned out the tank and discarded the contaminated diesel . Then this year I had the diesel polished as there were still tiny traces of black slime on the water trap filter when I serviced the engine last May.

[robert anthony]

Ok, so looks like I do have the bug. Luckily I had just got off the Severn when it blocked the fuel lines. I can get the boat back to the marina using the jerry can as a tank. So then drain the tank - how would be best to clean it once empty? Once clean I reckon ill only fill up with FAME free diesel in future.

[mango]

Anyone having a boat built should have the tank designed so that there is a low point from which water and muck can be drained regularly. A sump is even better and can be found on some boats with gravity fuel feed.

 

It's essential to make sure that rainwater cannot get in through deck fillers and vents. Diesel can absorb some moisture but if there is any significant amount, it will be rainwater or water added with the fuel.

[mango]

An odd bit of advice from RCR posted on narrowboatworld: Fuel treatments remove water and deal with contamination such as diesel bug, where enzymes, bacteria etc live off the water in diesel and affect the diesel properties.

 

I did not know that enzymes are alive.

[Guest]

Anyone having a boat built should have the tank designed so that there is a low point from which water and muck can be drained regularly. A sump is even better and can be found on some boats with gravity fuel feed.

 

It's essential to make sure that rainwater cannot get in through deck fillers and vents. Diesel can absorb some moisture but if there is any significant amount, it will be rainwater or water added with the fuel.

Amen to that. Nearly wrecked a nearly new engine a few years back because of a leaking filler seal. 50 pence for new seals, I renew ours frequently now, often after a full tank fill. Always a new one in spring and autumn whatever happens in between. Must cost me maximum two or three quid a year compared to a few hundred quids worth of diesel and treatment. Some on here argued this is foolish!

Edited October 24, 2015 by Guest

[mango]

Amen to that. Nearly wrecked a nearly new engine a few years back because of a leaking filler seal. 50 pence for new seals, I renew ours frequently now, often after a full tank fill. Always a new one in spring and autumn whatever happens in between. Must cost me maximum two or three quid a year compared to a few hundred quids worth of diesel and treatment. Some on here argued this is foolish!

The spill guard does not help because it helps collect rainwater for the diesel tank. A better solution is to have a raised filling point and a cap. I prefer this arrangement for drinking water too.

[Guest]

The spill guard does not help because it helps collect rainwater for the diesel tank. A better solution is to have a raised filling point and a cap. I prefer this arrangement for drinking water too.

Every time. My previous boat had the BSP pipe with a female BSP screw on cap. Much better arrangement. The brass jobbies might look posh, but sooner or later they leak; either the rubber seal, or the seal between the brass fitting and the steel deck. Never again.

[mango]

Every time. My previous boat had the BSP pipe with a female BSP screw on cap. Much better arrangement. The brass jobbies might look posh, but sooner or later they leak; either the rubber seal, or the seal between the brass fitting and the steel deck. Never again.

Many years ago I used to use a friend's narrow beam cruiser and the deck filler for diesel was marked 'water'. The owner never had the obvious accident but it's one of the many stupid things I've seen boaters do over the years. I'm glad it's a BSS requirement to label fillers correctly.

[mango]

I'm not convinced of the benefits of 'fuel polishing' unless attention is paid to removing diesel bug from the tank. I suspect it helps because people become aware of the need to keep their diesel tank free from water and debris.

 

Diesel bug does not seem to be a common problem in cars, but the fuel is stored in a nice clean plastic tank rather than a steel one. I suspect that it would help to have a plastic liner in diesel tanks on boats. 'Diesel bug' can be a mixture of bacteria, yeasts and filamentous fungi and all need water and various inorganic nutrients in addition to the fuel itself. A dirty steel tank can provide many of these nutrients.

 

Are there any boats with plastic tanks and do they suffer from diesel bug?

[churchward]

I'm not convinced of the benefits of 'fuel polishing' unless attention is paid to removing diesel bug from the tank. I suspect it helps because people become aware of the need to keep their diesel tank free from water and debris.

 

Diesel bug does not seem to be a common problem in cars, but the fuel is stored in a nice clean plastic tank rather than a steel one. I suspect that it would help to have a plastic liner in diesel tanks on boats. 'Diesel bug' can be a mixture of bacteria, yeasts and filamentous fungi and all need water and various inorganic nutrients in addition to the fuel itself. A dirty steel tank can provide many of these nutrients.

 

Are there any boats with plastic tanks and do they suffer from diesel bug?

I think it will be more to do with the frequency of fresh fuel being put into a diesel car and smaller tanks than it being made of plastic. Dirt and water could be introduced into the tank via the fuel in much the same way except it is more likely that a road side filling station again will have a higher turnover in fuel and also better management of the fuel condition.

 

A metal fuel tank particularly in the winter may suffer from condensation more than a plastic tank.

[mango]

I think it will be more to do with the frequency of fresh fuel being put into a diesel car and smaller tanks than it being made of plastic. Dirt and water could be introduced into the tank via the fuel in much the same way except it is more likely that a road side filling station again will have a higher turnover in fuel and also better management of the fuel condition.

 

A metal fuel tank particularly in the winter may suffer from condensation more than a plastic tank.

I accept that but bacteria etc. require various metal ions, including iron, to be able to grow. Where would they come from with a plastic tank?

[Arthur Brown]

Having burned a tank of diesel today, I can guess why cars don't get bug. Any bug I bought this morning is now thoroughly cooked.

 

Bug lives on the oil/water interface, if there is no water there is no bug habitat.

[Guest]

I suspect that the braking and acceleration of a road vehicle (not to mention g forces when cornering) will mix the diesel up more and the fuel filters will remove any crud present.

I suspect that the "stillness" and relative long storage time in the average canal boat cause most of the problems we are seeing. The storage at canalside facilities, unlike the fast turnaround at a supermarket pump must compound the problem.

[peterboat]

we have had a diesel x type with diesel bug it had stood for 9 months through winter with half a tank of diesel. the intank filter was solid black slime, we ended up removing tank and steam cleaning tank out, ok now

[mango]

I suspect that the braking and acceleration of a road vehicle (not to mention g forces when cornering) will mix the diesel up more and the fuel filters will remove any crud present.

I suspect that the "stillness" and relative long storage time in the average canal boat cause most of the problems we are seeing. The storage at canalside facilities, unlike the fast turnaround at a supermarket pump must compound the problem.

That's my assumption too. It's normal to have a recirculating system where fuel is pumped through a large filter and surplus flows back to the tank, effectively a small scale fuel polishing system that operates whenever the engine is running. Road diesel contains 7% biodiesel making it more hygroscopic but that will also help make it miscible with small amounts of water. We could learn something from road vehicles.

[bizzard]

And rain water along with leaves can enter your water tank filler too whilst filling up with water. A little filler umbrella can be made to prevent this quite simply with a pouring funnel.

Select a plastic funnel that your hose is a tight fit up its spout, or select a slightly smaller one and open it by cutting the tapered spout down bit by bit until the hose is a tight fit. Stuff the hose end up the spout until its end pokes well out of the bell end of the funnel, poke the hose into your orifice and see how it shelters and sheds off rain water and leaves whilst filling. A leaf in your water tank can cause all sorts of mysterious water stoppages, as it can in a fuel tank too. Voila.

Another little beggar that I think needs shelter is the fuel tank breather, the stubby thing sticking up with fire gauze mesh in it. I know rain shouldn't be able to enter through it and into the tank, but mmm I'm not so sure. To safeguard from this I have glued a small potted meat paste jar upside down on it as a shelter, but a short enough one so that a gap is left at the bottom so that the breather can still breath. Although one of these mounted on top of a breather that's stupidly mounted on top of a stern mooring dolly will keep getting busted off.

[churchward]

I accept that but bacteria etc. require various metal ions, including iron, to be able to grow. Where would they come from with a plastic tank?

Elements for bacterial growth can be introduced with the fuel. All of the required elements for growth will be contained in the fuel it is an organic and hydroscopic product after all. I don't think a metal tank helps but I don't think a plastic tank would eliminate the chances of getting the bug either. I am not sure passing the BSS would be easy with one either.

Edited October 25, 2015 by churchward

[churchward]

And rain water along with leaves can enter your water tank filler too whilst filling up with water. A little filler umbrella can be made to prevent this quite simply with a pouring funnel.

Select a plastic funnel that your hose is a tight fit up its spout, or select a slightly smaller one and open it by cutting the tapered spout down bit by bit until the hose is a tight fit. Stuff the hose end up the spout until its end pokes well out of the bell end of the funnel, poke the hose into your orifice and see how it shelters and sheds off rain water and leaves whilst filling. A leaf in your water tank can cause all sorts of mysterious water stoppages, as it can in a fuel tank too. Voila.

Another little beggar that I think needs shelter is the fuel tank breather, the stubby thing sticking up with fire gauze mesh in it. I know rain shouldn't be able to enter through it and into the tank, but mmm I'm not so sure. To safeguard from this I have glued a small potted meat paste jar upside down on it as a shelter, but a short enough one so that a gap is left at the bottom so that the breather can still breath. Although one of these mounted on top of a breather that's stupidly mounted on top of a stern mooring dolly will keep getting busted off.

All true I think. A significant source of water into the fuel is condensation running down into the tank from any air gap inside the tank especially when a boat is laid up for the winter.

[Guest]

That's my assumption too. It's normal to have a recirculating system where fuel is pumped through a large filter and surplus flows back to the tank, effectively a small scale fuel polishing system that operates whenever the engine is running. Road diesel contains 7% biodiesel making it more hygroscopic but that will also help make it miscible with small amounts of water. We could learn something from road vehicles.

That is something I have been mulling over; is that a good thing or a bad thing (from a boat point of view)?

I know some fuel additives (possibly Fortron?) encourage diesel to "soak up" small amounts of water and harmlessly burn it off. Some additives do the complete opposite and remove any water, presumably leaving it at the bottom of the boat tank. I think M16 is thus?

I have used both types over the years at different times, in the hopes that they will do their thing.

I also give the bottom of the tank a clean out with a piece of brake pipe connected to an electric pump. This can remove a surprising amount of crud.

I am still convinced that the brass type deck fillers can be a prime suspect for water contamination, unless the seal is maintained. As our boat gets laid up in the colder months I usually cover the deck filler with a large piece of plastic, and leave an upturned cup over the breather.

Over the years I have heard farmers claim that they add a little petrol or paraffin to diesel in vehicles that might only be used seasonally.

[furnessvale]

Amen to that. Nearly wrecked a nearly new engine a few years back because of a leaking filler seal. 50 pence for new seals, I renew ours frequently now, often after a full tank fill. Always a new one in spring and autumn whatever happens in between. Must cost me maximum two or three quid a year compared to a few hundred quids worth of diesel and treatment. Some on here argued this is foolish!

I had a customer once who swore blind I was supplying him with water contaminated diesel. Funny how it only affected his engine tank and not his separate gennie tank. Things came to head when he started bad mouthing me to other customers. A careful inspection revealed the filler housing had been badly fitted on his brand new boat allowing rainwater in.

 

George ex nb Alton retired

Edited October 25, 2015 by furnessvale

[Guest]

And rain water along with leaves can enter your water tank filler too whilst filling up with water. A little filler umbrella can be made to prevent this quite simply with a pouring funnel.

Select a plastic funnel that your hose is a tight fit up its spout, or select a slightly smaller one and open it by cutting the tapered spout down bit by bit until the hose is a tight fit. Stuff the hose end up the spout until its end pokes well out of the bell end of the funnel, poke the hose into your orifice and see how it shelters and sheds off rain water and leaves whilst filling. A leaf in your water tank can cause all sorts of mysterious water stoppages, as it can in a fuel tank too. Voila.

Another little beggar that I think needs shelter is the fuel tank breather, the stubby thing sticking up with fire gauze mesh in it. I know rain shouldn't be able to enter through it and into the tank, but mmm I'm not so sure. To safeguard from this I have glued a small potted meat paste jar upside down on it as a shelter, but a short enough one so that a gap is left at the bottom so that the breather can still breath. Although one of these mounted on top of a breather that's stupidly mounted on top of a stern mooring dolly will keep getting busted off.

Like the umbrella idea, and agree 100% about the stern dolly/breather stupidly mounted on top.

[furnessvale]

Many years ago I used to use a friend's narrow beam cruiser and the deck filler for diesel was marked 'water'. The owner never had the obvious accident but it's one of the many stupid things I've seen boaters do over the years. I'm glad it's a BSS requirement to label fillers correctly.

Unless the diesel filler is obviously on the back deck, a quick security fix for diesel thieves is to swap the water and diesel caps. Saves your diesel and gives him a problem!

 

George ex nb Alton retired