Jump to content


Photo

Sheeeit. Diesel bug!


  • Please log in to reply
50 replies to this topic

#1 Crazyhorse

Crazyhorse

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 474 posts
  • LocationUnexplored Northland

Posted 28 November 2018 - 02:20 PM

Noticed coming up the engine lost revs so suspected a fuel blockage, wasn't expecting to see the prefilter totally blocked with a brown sludge! We have a plastic tank so thought it wouldn't be prone to condensation ( Why doesn't this ever happen to trucks?). Seems I was very wrong. Easy enough to clean the filter, yet to check it after 7hrs running today but I am assuming it will need a clean again. We have used a bug killer last year but the 20lt container of diesel we added it to ended up with clumps of brown sh!t on the bottom. Is there anything that we can get that that will both kill and break this stuff up?
  • 0
""Some ships are designed to sink… others require our assistance."" Nathan Zelk, Commander US submarine Montpelier (SSN 765) 

#2 Fish

Fish

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 2,850 posts

Posted 28 November 2018 - 02:44 PM

Once you've got it, short story is no.

We've been through this in the past.

Its the biomass that is the issue, once it is there, it is there. You need to physically remove it, i.e. take the tank out of the boat, physically clean / wash / reinstall. 

If you can get at the tank in the boat, and have a good sized inspection hatch in it, you could maybe clean it effectively in place. (if you are patient, thorough, and like small spaces...) If your at all familiar with home brew, you are trying to getting the dead yeast sludgy sh*t out of the bottom of your fuel tank. 

 

Highly recommend what ever you do, put in a good quality primary fuel filter / water fuel separator with a glass bowl. You can see the sh*t in the bowl before your engine dies. If you are really fussy, put two filters in with valving to change from one to the other if one starts catching bug in it so you can continue motoring.

 

We did this batshit crazy thing and put the primary fuel filter where we can see it, just under the companion way stairs...

 

And just to cheer you up, bug can cause issues with your injectors. I'm not an expert in this area, but if you have a posh engine at all I believe the recommendation is to pull the injectors and get them checked. If you've got an old solid type of engine, I think bug in the injectors can cause knock, basically the symptom of uneven spraying of fuel into the cylinder.


  • 0

#3 Crazyhorse

Crazyhorse

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 474 posts
  • LocationUnexplored Northland

Posted 28 November 2018 - 03:17 PM

Thanks Fish. Not what I wanted to read! We have a still on board...make our own rum so yes, I know what you are saying! It's not feasible to get the tank out but was thinking of looping a pump through the filler and output via a bucket to sluice the stuff out until clean. So, what causes this gunk to grow in a bloody fuel tank? We close the breather when out for winter so not sure how the tank generates water? Driven trucks for years and never had this.
  • 0
""Some ships are designed to sink… others require our assistance."" Nathan Zelk, Commander US submarine Montpelier (SSN 765) 

#4 Fish

Fish

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 2,850 posts

Posted 28 November 2018 - 04:24 PM

Yes, sorry CH, DB is a major major pain in the arse, especially if you are in transit and your donk dies, you faf for ages fixing it, then it dies, then you faf for ages fixing it, then it goes fine, but then it dies...

Been there, so feel for you.

 

It is possibly still easiest to re-assess getting the tank out (even if getting it out is a major pain). If you can't, I'd put some effort into getting access to the very bottom of it via a drain plug or something (something lower than your normal diesel pick up). Maybe a siphon hose, vacuum pick up from an inspection hatch. The cause of the problem is at the very bottom of the tank.

You could set up a filter system and a recirculating pump. You can get small electic diesel pumps for less than $100 that will be ideal (we have one on our engine pick up re-circulation line).

Be prepared to spend some money on filters though. I can't recommend more strongly getting a good fuel / water separator filter. If you do, before permanently installing it, you could set it up in a re-circulation loop, run diesel through it for days and be prepared to change and clean the filter many many many times. I would get as much diesel out of the tank as possible and dump it. If you do this though, be prepared for it to fail again at any time in the future, when you least want it to. Do consider getting two filters in parallel, that you can swap from one to the other if you have a problem (if having a future donk die could be problematic for your safety).

 

Oh, and shake / stir the tank as if you are motoring into a gale, whilst filtering....

 

Diesel bug grows on the interface between diesel and water. Water sits on the bottom, so can be in your tank for years. There are 101 ways to get water into diesel. The most common is condensation, especially when parked up for a period, say like last winter, on the hardstand... No shaking, condensation can still occur on plastic, it is to do with relative humidity and surface temp. Plastic still cools to the same temp as steel, it has a lower heat capacity so takes less energy to change temp. It is a better insulator than steel, but it is the heat capacity that does it.

Water getting in from deck fitting / filler, breather pipe, esp if mounted on the stern.

Or, in the diesel you bought.

 

The fuel additives / biocides stop the bug growing on a fuel water interface. But once it has grown, you need to physically remove the biomass / sludge.

 

If you have bug,  I wouldn't put to sea (unless you can competently sail an engine-less boat) without physically getting into and removing the tank, or installing a good primary fuel water separator filter, or both.

 

and PS don't forget the injectors.


  • 0

#5 Neil

Neil

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 257 posts
  • LocationWaimauku, Auckland

Posted 28 November 2018 - 04:29 PM

Agree with fish. Early this year had the same problem although took a while to realise what it was as the debris in the tank was blocking the outlet pipe inside the tank (and not all the time) and thus we didn't see the filter get messed up. Ended up taking tank out and cleaning it. We also put big inspection hatches on it so I could do the job in situ next time.

 

Here's the discussion: http://crew.org.nz/f...n-diesel-lines/


  • 0

#6 harrytom

harrytom

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 1,446 posts
  • LocationAuckland

Posted 28 November 2018 - 04:36 PM

The microbes have a very short life but before they die they multiply and produce waste deposits, both of which descend to the bottom of the fuel tank. One bacteria microbe can reproduce more than 7 million microbes in 24 hours. Due to the rate of reproduction and their short lives, the build-up of dead microbes can be quite fast.

Any fuel tank with an air pocket will produce condensation when the temperature falls far enough, and is therefore likely to attract these tiny microbes. After a day out on the road, the remaining diesel is warm from the heat of the engine and as the temperature cools, cold air is drawn into the fuel tank. The cold air causes condensation on the inside of the tank, forming dense water that eventually sinks to the bottom of the fuel tank. In that water are the microbes as they live off the oxygen in the water and then eat the diesel.

 

"CH" now why dont trucks get the bug simple answer is,tank is really left empty,always being topped up,unlike yachts/launches. We tend to use vessel,turn everything off and go out again in fortnight,tank usually 1/2 to 3/4 full.So we really should keep tank full and use a good additive to prevent bug. Undetected bug not only clogs filters but gets in the fuel pump and govner system next minute $1500 for new pump etc we could not of been lazy and used the additive/top tank off and of course used vessel more often.


  • 0
The boss said "see you in the morning"didnt know he liked sailing

#7 Priscilla II

Priscilla II

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 935 posts

Posted 28 November 2018 - 04:39 PM

Bug sits in the dark and has sex. Crikey what a life.

I had a guts full of this engine stopping promiscuous behaviour so built a tank that has a sump with drain valve.

No unsolicited humpy pumpy going on now.

HT is most correct keep the tank full and I am of the opinion that any topical additives are rarely 100% effective. 

EXNwBQA.jpg


  • 0

#8 Fish

Fish

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 2,850 posts

Posted 28 November 2018 - 04:50 PM

Jokes aside, diesel bug is the kind of condition that may well warrant counselling...

 

The grief process usually starts with denile.

then hope there is an easy solution

then ignoring it for awhile, often accompanied by thoughts of golf or lawn bowls

slowly, given time, there is a gradual realisation that to beat the little feckers fornicating in the bottom of the fuel tank, there is no easy fix.

Following the realisation stage is a grim determination to fix it properly, once and for all, regardless of the amount of effort and boat disassembling is required.


  • 0

#9 Crazyhorse

Crazyhorse

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 474 posts
  • LocationUnexplored Northland

Posted 29 November 2018 - 07:09 AM

Nice bloke...you are full of joy Fishy!! Unfortunately I think you are right. Looked at the prefilter this morning and clean after 7hrs running. Another problem is trying to stop a fuel filter glass bowl from leaking. Can never get those bloody rubber seals to sit right in the glass bowl and not leak when done up. Any tricks?
Here's a (silly?) idea. To kill the bug forever and never have to worry about getting it in the first place, build into tanks some UV leds! Hit the switch now and again and dead!
  • 0
""Some ships are designed to sink… others require our assistance."" Nathan Zelk, Commander US submarine Montpelier (SSN 765) 

#10 Jon

Jon

    Advanced Member

  • Advanced Members
  • PipPipPip
  • 1,742 posts
  • LocationSouth of the Bombays

Posted 29 November 2018 - 07:55 AM

What could possibly go wrong with 12 volt light fittings in your fuel supply ?
  • 0
The best sailors do it two handed




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users