Diesel Bug

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Nicholas123

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I have been reading reports about this & am wondering if I am going to get it.

I have a pretty big plastic fuel tank that just has a few gallons slopping around in the bottom.It's been like that for a year with no problems but now I read that it is condensation that causes it.So do you get condensation from a plastic surface to the extent that I am vulnerable?
(I know that the cold on a metal surface like stainless steel will cause condensation & I cannot afford to fill the tank right up as has been recommended in the yachting articles I have been reading recently).
 
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You can still get condensation inside a plastic tank. If you're worried about diesel bug, it would be worth shock dosing the fuel now with a bug killer such as Grotamar or Marine16.
 
condensation will occur in any tank with a large volume of air relative to the vol of diesel.

If your diesel contains 'bio' then it is likely to acquire the bug more easily than old-style diesel.

Can you drain the tank ?

Do you have a water separater in the fuel line before the filter ?

Do you have a pre-main filter ?

Do you have an easily changeable main fuel filter, with spare filter(s) ?


I'd buy or cadge a small bottle of the recommended bug killer, dose the tank, and depending on your approach to risk, leave the fuel in overwinter and use it next year.

But the ideal is to remove the fuel, dose it, take it home overwinter in a container which is as full as possible, store it cold, and then use it next year, having cleaned the tank and changed filters. All fiddly stuff, but that will reduce the risk of acquiring the bacteria through the vent or filler or bio-diesel, and a clean tank is always a good start to the season. One thing less to worry about :)
 
sarabande said:
condensation will occur in any tank with a large volume of air relative to the vol of diesel.

If your diesel contains 'bio' then it is likely to acquire the bug more easily than old-style diesel.

Can you drain the tank ?

Do you have a water separater in the fuel line before the filter ?

Do you have a pre-main filter ?

Do you have an easily changeable main fuel filter, with spare filter(s) ?


I'd buy or cadge a small bottle of the recommended bug killer, dose the tank, and depending on your approach to risk, leave the fuel in overwinter and use it next year.

But the ideal is to remove the fuel, dose it, take it home overwinter in a container which is as full as possible, store it cold, and then use it next year, having cleaned the tank and changed filters. All fiddly stuff, but that will reduce the risk of acquiring the bacteria through the vent or filler or bio-diesel, and a clean tank is always a good start to the season. One thing less to worry about :)
Click to expand...

I can't drain the tank easily.There dos'nt seem to be any drain plug at the bottom but I would'nt really know as the bottom is inaccessible.There is a sort of inspection hatch half way up the back that I can just about get to but it would be a hell of a palaver.
There is a water separator thing if that is what it is.It is clear glass & there is a screw at the bottom that you can unscrew I believe to drain out the water.There is another filter before the fuel line goes to the injector but I do not have a spare filter at the moment & want to avoid bleeding the whole system.
If I blocked the air vent to the tank would'nt that prevent any more water entering the system thereby alleviating the risk?
 
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At the beginning of the season when I changed my primary filter I found some black strands in it but it was far from blocked. I opened the inspection hatch and saw this:



I shocked the system with Grotamar and checked the filter several times during the season and found it all clean:

[URL=http://s217.photobucket.com/user/rgaspar_album/media/P1000716.jpg.html]

On laying up, I had run down the tank to about half full and opened it up again and found this:

[URL=http://s217.photobucket.com/user/rgaspar_album/media/P1000803.jpg.html]

Having drained the cleanish stuff, I have this at the bottom:

[URL=http://s217.photobucket.com/user/rgaspar_album/media/P1000824.jpg.html]

It is 20 years since I last drained and cleaned the tank (which had no crud in it then). So is this just natural crud of 20 years use or the bug?
 
sarabande said:
condensation will occur in any tank with a large volume of air relative to the vol of diesel.
Click to expand...

I read an article recently in which some research into this widely held belief showed that in fact it doesn't happen. Presumably whatever moisture might have been in the air that entered as the fuel level reduced could condense but that is a very small amount. The air in the tank remained there, with no further ingress of moisture. Unfortunately I don't remember where I read it so cannot reference it.

Many fuel bunkers are contaminated with water, so maybe that is the major source?
 
vyv_cox said:
Many fuel bunkers are contaminated with water, so maybe that is the major source?
Click to expand...

I think many will agree with this, it has to be fuel supply source where water and bug contamination first starts. I have a 0.5 litre sump built into the bottom of my fuel tank with a drain tap which is easily got at. I take a fuel sample a short time after taking fuel on board and I try and get fuel from marine stations which would have a high fuel turnover, (like a marina which has lots of big thirsty motor boats). But I also dose with a fuel bug additive at every fuel top up. Careful examination of your removed primary filter when you change it will also tell you a lot about the state of your fuel and tank.
 
tillergirl said:
It is 20 years since I last drained and cleaned the tank (which had no crud in it then). So is this just natural crud of 20 years use or the bug?
Click to expand...

Without checking with one of the fuel bug kits it is difficult to say and since the kit is the same price as a dose of Marine 16 I just went ahead and dosed the tank after finding this. The fuel looked clean and there was only half a teaspoon of black stuff each year in the water separator but decided to go ahead and open up the tank any way. I used a small electric facet fuel pump with a CAV filter to drain the the tank down. Next using a wall paper scraper scrapped and scooped out the gloop into a plastic container before giving the tank a good wipe with 1/2 an old bath towel. I then put a few cup fulls of clean diesel back in and used a scotchbrite pan cleaner to scrub the tank out and again another clean with remaining towel. Starting with fresh clean diesel I have given the tank a shock dose of Marine 16, cleaned out the water separator and replaced the engine fuel filter. Ran the engine and Webasto heater hard for 30 minutes to flush the Marine 16 around the system.

I also replaced the fuel filler cap and seal as I think this was how water was getting into the tank. Marigolds and lots of plastic bags plus kitchen roll required for this job. Top tip, Waitrose marigolds have a lining which helps get them on and off a second time.

http://www.marine16.co.uk/acatalog/Fuel_Treatment_Products.html

Before:

CF9_zpsba3bd063.jpg


CFFuelTank1_zps2e74f7a3.jpg


CFFuelTank2_zps14eac4ac.jpg


After:


CFFuelTank6_zpsb26f3a34.jpg


CFFuelTank5_zps5ebd52e3.jpg


Pete
 
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This was the filter off the CAV unit used to drain the tank. As I said, there wasn't any real signs of the scale of the problem until I opened up the tank.


Pete

CavFilter_zps197b000e.jpg
 
pvb said:
You can still get condensation inside a plastic tank. If you're worried about diesel bug, it would be worth shock dosing the fuel now with a bug killer such as Grotamar or Marine16.
Click to expand...
Thanks for those names. On one of the sites (Marine 16) it gives a link to a pbo diesel treatment test. The one I was using before the one I am now was found not to work at all !
 
Pete7 said:
This was the filter off the CAV unit used to drain the tank. As I said, there wasn't any real signs of the scale of the problem until I opened up the tank.


Pete

CavFilter_zps197b000e.jpg
Click to expand...

My filter at the beginning of this season was marginally better than that but I guess my tank is like yours. Like you it's not going to be difficult to clean - just messy.
 
I can't help thinking that the refineries are dispensing a pretty disgraceful product here & am wondering if they are benefiting from flogging us all these expensive additives?
If as tillergirl says she/he? had no problems 20 years ago what the hell is going on!:mad:
 
Nicholas123 said:
I can't help thinking that the refineries are dispensing a pretty disgraceful product here & am wondering if they are benefiting from flogging us all these expensive additives?
If as tillergirl says she/he? had no problems 20 years ago what the hell is going on!:mad:
Click to expand...

I first came across diesel bug in the late 1980's! while working at a major construction equipment factory. It was in the in-factory (above ground) fuel storage tanks. No one knew about fuel bugs back then, it was mainly seen as a water ingress problem. It took months before the fuel supply company came up with some kind of additive and suggestions, but it was very experimental at the time. I am sure the bug has been around for a long time, it was probably just put down as "bad or dirty fuel" caused by poor storage facilities.
 
vyv_cox said:
I read an article recently in which some research into this widely held belief showed that in fact it doesn't happen. Presumably whatever moisture might have been in the air that entered as the fuel level reduced could condense but that is a very small amount.....
Click to expand...
Nigel Calder wrote an article with mathematical calculations which showed that no way could an average yacht have enough air volume to cause enough condensation to cause a problem. Most likely ALL bugs from filling stations with enough water for them to breed.

We use bug inhibitor but always have bugs in our tanks and clean out the sludge every two years.If they don't get to the glass bowl of your primary fuel filter then you are OK.

I fitted two inspection lids to aid with the cleaning. Suck/pump out as much diesel as you can and then cut a whole in the tank - all debris and the diesel will be thrown anyway. TekTanks do a very nice inspection lid that doesn't need any bolts/glue but an O ring washer - easy to fit to Polyethelene tanks.
 
pvb said:
Sludge would be trapped by the filter element before it reaches the glass bowl.
Click to expand...

I think he was talking about a separate water widget then the engine filter, but you are right about the CAV type as shown in my photo above from my fuel filtering rig. Makes me wonder if it would be better to connect the filter the other way around so dirty fuel goes to the bottom section glass bowl then up through the filter. You would see a problem developing much quicker. See the last part of this web page:

http://ckdboats.blogspot.co.uk/2009_11_25_archive.html

Pete
 
Pete7 said:
I think he was talking about a separate water widget then the engine filter, but you are right about the CAV type as shown in my photo above from my fuel filtering rig. Makes me wonder if it would be better to connect the filter the other way around so dirty fuel goes to the bottom section glass bowl then up through the filter. You would see a problem developing much quicker. See the last part of this web page:

http://ckdboats.blogspot.co.uk/2009_11_25_archive.html
Click to expand...

In your blog, you suggest that the CAV-type filter head has the in/out arrows incorrectly marked. This isn't the case. The unit is designed so that fuel goes in to the filter first, then down into the glass bowl, then up through the centre of the filter and out. The reason for this is that minute droplets of water in the fuel are agglomerated as they pass through the filter into larger droplets which can fall to the bottom of the glass bowl. If you plumb it the wrong way round, any water droplets will pass through to the engine.
 
pvb said:
The reason for this is that minute droplets of water in the fuel are agglomerated as they pass through the filter into larger droplets which can fall to the bottom of the glass bowl. If you plumb it the wrong way round, any water droplets will pass through to the engine.
Click to expand...
Thanks, I've wondered why that was.
 
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