Milky diesel - diesel bug?

[neil1967]

I have just checked my diesel filter, which has a clear bowl, and the diesel looks milky. The diesel in the tank is the same, but I know it was clear about a month ago when I polished the diesel, and in fact the diesel in the filter bowl was clear 2 days ago, as I checked it before I went sailing. The diesel is predominantly white diesel, but there will be some traces of red in it. We are in Portugal so the weather is consistently hot during the summer, but we have been here for 5 years without a problem previously. I’m not sure it is diesel bug as that tends to form at the interface of diesel and water, rather than being throughout the liquid. Any thoughts?

 

[Refueler]

Milky Diesel is usually from Emulsification with water ... or in cold temps the parafins start to form and cloud the diesel ..

You are in 'hot' climate so its not cloud point. Your diesel will by EU standards have a level of Bio in it .. likely 10% ... and this may have taken up moisture.

Unless of a high % water - this actually should not be any concern to the engine ... its more a visual matter.

Its interesting actually that we are seeing odd whole ships cargoes with similar .. and no-one has an explanation of why. We are running a lot of tests to determine .. lab tests all show ON specification - apart from the Turbidity.

 

[neil1967]

Milky Diesel is usually from Emulsification with water ... or in cold temps the parafins start to form and cloud the diesel ..

You are in 'hot' climate so its not cloud point. Your diesel will by EU standards have a level of Bio in it .. likely 10% ... and this may have taken up moisture.

Unless of a high % water - this actually should not be any concern to the engine ... its more a visual matter.

Its interesting actually that we are seeing odd whole ships cargoes with similar .. and no-one has an explanation of why. We are running a lot of tests to determine .. lab tests all show ON specification - apart from the Turbidity.

Refueler, that’s really interesting, thank you. Our primary filter is a Racor R12T, 10 micron, which is where the problem became evident. We also have a Baldwin BF790 secondary filter, mounted on the engine which I believe is 30 micron, and the engine is a Perkins 4108. We had no problems running the engine - and you seem to be suggesting that I can carry on as normal? Is it worth trying to polish the fuel - I have a racor 2 micron filter and separate fuel pump that I could use for this, but not much point if it won’t remove the emulsified water.

 

[B27]

Has the fuel been dosed with anything?

 

[neil1967]

Has the fuel been dosed with anything?

It was dosed with Marine 16 fuel set about 3 -4 weeks ago and has been run for about 4-5 hours since then, but the problem has only been apparent in the last 2 days. I am quite assiduous in checking the fuel filter bowl before every trip.

 

[Refueler]

I doubt very much 'polishing' will do anything .... the filters you have are all designed for solid / particulate removal ...

M16 does very little in terms of moisture content of fuel.

Perkins 4-108 ? I have 4-107 and I run whatever is in tank through mine ... she purrs along all day long ...

 

[neil1967]

I doubt very much 'polishing' will do anything .... the filters you have are all designed for solid / particulate removal ...

M16 does very little in terms of moisture content of fuel.

Perkins 4-108 ? I have 4-107 and I run whatever is in tank through mine ... she purrs along all day long ...

OK, I think I’ll give it a test run under load and if all is ok after that I’ll stop worrying about it! Thanks again.

 

[thinwater]

... Its interesting actually that we are seeing odd whole ships cargoes with similar .. and no-one has an explanation of why. We are running a lot of tests to determine .. lab tests all show ON specification - apart from the Turbidity.

Looking with a microscope can sometimes help. Very small (1 to a few microns) water drops, for example, can do this without contributing much water. Too small to coalesce, and as you say, basically harmless. They sometimes form in fuel that was somehow saturated with dissolved water in warm conditions and then chilled.

But this probably does not relate to the OP's problem. Water is usually from a leaky filler cap.

 

[B27]

It was dosed with Marine 16 fuel set about 3 -4 weeks ago and has been run for about 4-5 hours since then, but the problem has only been apparent in the last 2 days. I am quite assiduous in checking the fuel filter bowl before every trip.

'Fuel Set' and 'Marine 16' are different things?
They work or not, in different ways.
I would personally check the bottom of the tank for free water.

If you are concerned about the diesel, then a silica gel based water removal treatment is sometimes advocated.
If you have Marine 16 fuel treatment (as opposed to their bug killer), it's supposed to be a demulsifier so you could try dosing a sample and seeing if it drops the water out?

 

[Oily Rag]

If water entered through the filler cap then it would fairly quickly enter the fuel piping system. Any not caught by the filters would be atomised by the pumps and would return via the leak-off pipe to the tank. So you could fairly quickly get milky diesel.
But is that a problem?

 

[thinwater]

...If you are concerned about the diesel, then a silica gel based water removal treatment is sometimes advocated....

Could you be specific? I'm interested. I'm guessing you mean some type of filter media in a cartridge, but specifics would be helpful. I assume you are talking about polishing out ppm levels, not percent levels.

 

[B27]

There are various companies advertising diesel drying and 'recovery' of 'waste' fuel based on extracting water from diesel.

There is plenty of opinion saying emulsified diesel can be bad for engines.
I think we could be talking about high numbers of ppm up to a per cent or so?
I can't recommend specific vendors.

 

[Refueler]

"neil1967" ..... How many litres of fuel in the tank ?

If its not so much ... why not drain off .... add some additive and see what happens ?

 

[bluerm166]

In my experience after a blocked primary filter ,leading to draining 40L of diesel into clear wall 5L containers ,and then gravity filtering through a spare CAV rig,away from the boat,water in the diesel ,shaken up to an emulsion,will separate within about half an hour.Impurities and bug debris sink within this period .This is what is happening in the tank when conditions allow it to settle.So muck will generally end up in the bottom of the tank (some may cling to the walls) unless it is constantly churning in a rough sea,aided by a low fuel level.
Draining the settled tank with a Pela by progressive lowering of the dip pipe shows that the upper 30 to 35 litres has imperceptible water content and very little particles.These settle out visibly to show on the clear bottom of the container and can be separated simply by slow decanting.
The remaining 5L in the tank can be agitated with the bulk of impurities removed in suspension,again ,because of access limited ,with the Pela.Repeated and repeated and using a temporary copper 8mm dip pipe as a stirrer and directed all around the tank base.So only about 3 x 5L really need filtering on the rig,and only the small residue of decantering needs to be thrown away responsibly.
The filter bowl had previously been clear and the engine was happy crossing sections of the channel.The damage was done passing down the Ramsgate entrance channel in the higgledy piggeldy sea that the banks and tide generate there.
If you have a dip tube like mine that is held by a compression fitting on the tank top you can raise the dip tube temporarily ( a simple clamp) to help you get back.Especially if it has been originally positioned so low in the tank as to be pushing your luck.Photos here show the separated muck drained from the bowl and settled and the cleaned fuel.The tank is nom. 300 x 400 x 600 high.Fresh fuel is treated with B16.
IMG20240709114615.jpgIMG20231018142058.jpg
Obviously if you have a tank that can be drained from the base and/or has good access from the top you can avoid this mullarky.

 

[Refueler]

Emulsified Fuel does not settle out water .... it may drop a small amount but main part is suspended and needs additive to cause it to break and separate.

Suggestions of heating - doesn't work ........ freezing - even worse as that will cause Parafins to crystalize.

You cannot filter water from emulsified fuel.

 

[thinwater]

The simplest (and safe way) to pump right from the bottom, to pull free water and some dirt, is to use an oil change pump and a semi-flexible stinger that will reach the lowest point (cut on an angle). move it around a little if practical. Your fuel suction does not reach the very bottom.

 

[bluerm166]

Neils issue suggests that whether this is truly emulsified or not and was previously clear :
The tank already had contaminants,possibly water in it that were not cleared during 'polishing' and these were entrained by use of a high speed pump during the polishing .
Or contaminants,water or detergent were used in the tank or lines and not cleared before refilling.
Or water was introduced in a fuel top up.
But it doesn't sound easy to emulsify - is it possible that an injector can blow back ,probably not ?
I see that Wynns make an inexpensive water remover - £ 10 for their ' DRY FUEL' product that treats 60 litres of diesel or petrol,but I can't find any detailed application guidance.

 

[Beneteau381]

If water entered through the filler cap then it would fairly quickly enter the fuel piping system. Any not caught by the filters would be atomised by the pumps and would return via the leak-off pipe to the tank. So you could fairly quickly get milky diesel.
But is that a problem?

Atomised by the pumps then return via the leak off pipes? Do you understand how the injection system works?

 

[Beneteau381]

Neils issue suggests that whether this is truly emulsified or not and was previously clear :
The tank already had contaminants,possibly water in it that were not cleared during 'polishing' and these were entrained by use of a high speed pump during the polishing .
Or contaminants,water or detergent were used in the tank or lines and not cleared before refilling.
Or water was introduced in a fuel top up.
But it doesn't sound easy to emulsify - is it possible that an injector can blow back ,probably not ?
I see that Wynns make an inexpensive water remover - £ 10 for their ' DRY FUEL' product that treats 60 litres of diesel or petrol,but I can't find any detailed application guidance.

I suspect that that product is basically alcohol which will pickup the water.

 

[Beneteau381]

Neils issue suggests that whether this is truly emulsified or not and was previously clear :
The tank already had contaminants,possibly water in it that were not cleared during 'polishing' and these were entrained by use of a high speed pump during the polishing .
Or contaminants,water or detergent were used in the tank or lines and not cleared before refilling.
Or water was introduced in a fuel top up.
But it doesn't sound easy to emulsify - is it possible that an injector can blow back ,probably not ?
I see that Wynns make an inexpensive water remover - £ 10 for their ' DRY FUEL' product that treats 60 litres of diesel or petrol,but I can't find any detailed application guidance.

The injection system works by a low pressure lift pump delivering fuel to the high pressure injection pump which delivers fuel to the injectors at the correct moment defined by the timing. The fuel enters the injector body where there is a spring loaded valve which pops open at a predetermined pressure which allows the fuel to pass through the injector nozzles where it is atomised in to the cylinder. The injector bodies are full of fuel which cools them and excess is returned to the fuel tank through the leak off pipes. Blow back? No.
So water in the fuel. Fill cap? Source? Does it matter? Deal with it. I would get in to the tank and see if there is any free water in the bottom. Deal with that and then think of how to deal with the emulsification, if that is what it is.
I saw earlier on that the OP talked about primary and secondary filters with I think him swopping around their descriptions. The primary is the one straight out of the tank, secondary usually on the engine. So 10 micron would be advisable for the primary followed by 5 micron for the secondary. Most systems including the venerable CAV 296 should spin out emulsified water. He could as you suggest use a Wynn’s product to try and trap the water if that is what it is