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Diesel bug


Roger Beattie

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Diesel bug grows at the interface between diesel and water. Keep water out and there can be no diesel bug.  However, given that not all suppliers supply water-free fuel this is easier said than done.

 

There are various fuel treatments on the market.  Generally these are either biocides which kill the bugs or chemicals which cause the water to be dissolved in the diesel, so there is no water interface for the bugs to live in.  The watery diesel is then burned by the engine.

So  practically,  the best practice is to keep your tank full, to reduce condensation, dip it regularly with water finding paste on the end of the dipstick  and pump out or drain off any water that is found, and then as back up, treat each fill-up with a fuel treatment of your choice. 

 

Biocides do not address the non-bug related problems of having water in the fuel and killing a bug colony does not stop it blocking up your filters.

Water dispersants have a finite capacity to disperse water so a bad attack of water may not all be dissolved. There are concerns too about the long-term effect of a solution of water in diesel on fuel pumps and injectors, particularly if the water drops out of solution

 

You pays yer money.....

 

N

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I got the bug as a result of a poor setup of my breather. 

Had to change my primary fuel filter in the pouring rain on the river Lee.

I now xx years later still bung a dose of 'snake oil' at every top up - just-in-case.

 

It's not mandatory - if you don't know how to change a filter / don't want to go down the engine hole in any weather then bung some in....

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Pretty much as the other posts.
That water finding paste is excellent, and does seem a tad expensive but lasts a long time. Turns red at a hint of water.
I use Marine 16 complete most of the time, sometimes I switch to Fuel set for a year. They appear to work, but I always think of the old joke about the guy in Liverpool painting around his house with crocodile repellent....
I am fussy where I fill up and try to use places with a high turnover. I note that some suppliers (Venetian Marine on the Middlewitch for example) add Marine 16 to their fuel when delivered.
I buy fame free diesel if available, but not sure if there is any advantage.
Tank level as high as possible in winter though not always easy as we use the engine all winter.

Edited by Guest
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1). Buy diesel from a source that sells a lot and has a reputation to keep, they are less likely to have water in their fuel.  

2). Use the boat so you turn over your own diesel

3). Keep it full over winter, especially if you leave it for weeks, the more empty space the more wet air gets pulled in as the tank cools and warms every day.

4). Every spring check for water at the bottom of the tank, and remove it if there is.

 

 

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Another point: We go in the car and collect diesel during the winter when I see some people putting diesel in filthy containers. I am no expert, but can't see how this would help keep diesel in good fettle. I keep cans specifically for the job and keep them clean.

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21 minutes ago, Chewbacka said:

1). Buy diesel from a source that sells a lot and has a reputation to keep, they are less likely to have water in their fuel.  

2). Use the boat so you turn over your own diesel

3). Keep it full over winter, especially if you leave it for weeks, the more empty space the more wet air gets pulled in as the tank cools and warms every day.

4). Every spring check for water at the bottom of the tank, and remove it if there is.

 

 

Spot on. I never use any additives and have never seen the bug in thirty years continuous boat ownership.  Just burn plenty of diesel and replenish from busy places whenever possible. I try to use hire fleet bases wherever possible or busy coal/fuel boats. from what I have seen over the years its usualy but not exclusively hobby boats that seem to suffer with this problem that are often left long periods of time not in use. Spose I will get the bug now lol.

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6 minutes ago, dccruiser said:

I have a fuelguard fitted with a return system so i can even "polish" my own fuel ... cant recommend it highly enough.

 

Rick

And are you pumping it round fast enough to pick up water from the base of the tank?

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7 minutes ago, ditchcrawler said:

And are you pumping it round fast enough to pick up water from the base of the tank?

I believe so as the return system has a high pressure face electric pump doing the work and is using the tank pick up :) 

 

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We had an MLS fuel purifier fitted to deal with an issue of water in the fuel from a leaking filler cap.  Now I just drain the purifier occasionally to see the condition of the fuel and if it is clean put it back in the tank.

Edited by Rob-M
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Go easy on the biocide. Use it, after removing water, and contaminated product as a final clean up by all means, but routine biocide use will just accelerate the evolution of biocide resistant bugs,, and not only in fuel.

I recently purchased a hand opertated brass double acting pump and a length of copper tube that could be shaped, to be able to scavenge the bottom of the fuel tank of the yacht appearing as my avatar. From a 150litre tank  Pulled about 500ml of free water with a heavily bug contaminated interface, but after a further litre fuel clear. Will do another scavenge before next Saturdays race. I would expect to need to dump another 1.5litre of mildly contaminated fuel but the amount encountered will determine the timing of the scavenge. It is now on the at least every six months list.

Much preferable to find the bug in the bottom of the sample bottle then in the fuel filters of a silent engine.

Edited by DandV
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11 hours ago, Rob-M said:

We had an MLS fuel purifier fitted to deal with an issue of water in the fuel from a leaking filler cap.  Now I just drain the purifier occasionally to see the condition of the fuel and if it is clean put it back in the tank.

A good point. I have owned boats with the stupid flush deck fittings with the brass screw in filler stop, they look pretty but are bloody stupid. I didnt think about them at the time but my present boat has the much more sensible threaded upstand pipe with a domed cap on so you could jet wash it for hours and it will not let rain in. There are some realy stupid designs of basic fittings on so many boats innitt. iirc my Udson had the daft flush fitting but my good old cheapo colecraft has the sensible one.

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13 minutes ago, mrsmelly said:

A good point. I have owned boats with the stupid flush deck fittings with the brass screw in filler stop, they look pretty but are bloody stupid. I didnt think about them at the time but my present boat has the much more sensible threaded upstand pipe with a domed cap on so you could jet wash it for hours and it will not let rain in. There are some realy stupid designs of basic fittings on so many boats innitt. iirc my Udson had the daft flush fitting but my good old cheapo colecraft has the sensible one.

My clolecraft has the same arrangement using a black iron screw on cap.  It would sometimes be difficult to unscrew as rust forms on the threads, so I swapped it for a stainless cap, just a few quid on eBay, perfect.

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3 hours ago, mrsmelly said:

A good point. I have owned boats with the stupid flush deck fittings with the brass screw in filler stop, they look pretty but are bloody stupid. I didnt think about them at the time but my present boat has the much more sensible threaded upstand pipe with a domed cap on so you could jet wash it for hours and it will not let rain in. There are some realy stupid designs of basic fittings on so many boats innitt. iirc my Udson had the daft flush fitting but my good old cheapo colecraft has the sensible one.

 

I agree. I have one of them flush deck fillers on one of my botes. As it happens, the cap thread is 1.5" BSP so I've screwed (and sealed) a 1.5" brass barrel nipple into it to create an upstand, with a nice brass 1.5" cap screwed onto the top.

 

I don't trip over it very often...

 

 

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43 minutes ago, Mike the Boilerman said:

 

I agree. I have one of them flush deck fillers on one of my botes. As it happens, the cap thread is 1.5" BSP so I've screwed (and sealed) a 1.5" brass barrel nipple into it to create an upstand, with a nice brass 1.5" cap screwed onto the top.

 

I don't trip over it very often...

 

 

Aye that's the rub...

A sensible fuel fuel filler arrangement works well on a cruiser stern - but for a boat with a proper back end - any sticky-up-bits are a complete pain. Perhaps I've been lucky over the years (or mebe  using the right  sort of snake oil)  that I've never had a repeat of the bug. 

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Sorry for the slight highjack - I’d appreciate any recommendations for a suitable manual or 12v pump or siphon to remove any water found from a trad stern fuel tank.

Also to take samples to visually inspect the fuel from the bottom of the tank, to supplement the water indicating paste that I have on order.

 

Should I opt for a manual or electric solution?

 

Most of the electric pumps I’ve seen for diesel are the submergible type which I’m guessing is less ideal than ones where just a long hose is inserted to various parts of the bottom of the tank?

 

Thanks.

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4 minutes ago, gbclive said:

Sorry for the slight highjack - I’d appreciate any recommendations for a suitable manual or 12v pump or siphon to remove any water found from a trad stern fuel tank.

Also to take samples to visually inspect the fuel from the bottom of the tank, to supplement the water indicating paste that I have on order.

 

Should I opt for a manual or electric solution?

 

Most of the electric pumps I’ve seen for diesel are the submergible type which I’m guessing is less ideal than ones where just a long hose is inserted to various parts of the bottom of the tank?

 

Thanks.

Unless you're doomed - and the tank has lots and lots of water (in which case, yo are...) then my suggestion is a Pela pump - that's what I use.

with a stiff piece of pipe = 8mm  c/h copper pipe you can poke around easily and pick up any grot as well

Gosh they're pricey... Amazon do a look alike version for  twenty five quid - but I don't know how good it is...

 

I have found with a 'leccy pump that the output thrashes about  - so you have to monitor both ends at one. You have more control with a manual type.

If you're really mean you can get a manual pump with two lengths of pipe one of which always come adrift while you work...

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Yes, a Pella pump will do it unless there is a lot of welding scale , dust and similar in the bottom. Then the tube tends to block. I now use a length of clear plastic 3/8" bore plastic tube and some milk cartoons sitting in the bilge. I just set up a syphon with a suck. However I have had a lifetime of inadvertent mouthfuls of diesel or petrol and image some would not like this nice simple and controllable method.

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Thanks for the suggestion - I’m probably uniquely incompetent, but I did not get on with my highly recommended Pella pump for emptying the oil sump of our Kelvin.

I ran out of hands to hold the container steady, hold the pump cylinder in place on top of its reservoir, then pump the pump whilst holding the suction pipe accurately in place (what a mess!).

So for that job I now successfully use a Lidl 12V oil pump?

As I have one, I’ll give it a try, but it will need to be either a “2 crew” or 1 octopus operation.

 

Any other recommendations please?

 

Edited by gbclive
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