Sludge or bug?

[chris-s]

In preparation for the new season, today’s job was to change the fuel filters and wake up the engine.

Just for giggles I decided to cut open the primary filter and found this….




Sludge or bug?

We’ve had the boat for a season, have always dosed with marine 16 fuel complete and filled the tank to overflowing back in October when we were hauled out.

Last spring before launching I rigged up a filter, pump and rigid pipe to clean out the tank thru the sender hole, not a lot came out but probably worth doing again.

 

[lusitano]

Sludge - Bug is like jelly

 

[William_H]

Yes well worth sucking out the bottom of the tank again. Water sludge or bug you want it out anyway. ol'will

 

[thinwater]

Could be both. But ...

... Explain why the boat has sludge but the diesel pick-up truck does not. It is not normal fuel aging. Diesel last for years, nearly a decade, properly stored. It's not from the supply; in the US, at least, they have 10 micron filters on the pumps and the truckers would kill if the fuel were dirty.

So where is the sludge from?

 

[Bandit]

Bug and probably a dirty tank that needs, treating, cleaning and the remaining fuel polished or dumped.

 

[Refueler]

Bug and probably a dirty tank that needs, treating, cleaning and the remaining fuel polished or dumped.

mmmmm not in my book ! Dumped ?? Really ?

Black gunk like OP shows is not uncommon .. and TBH - the filter if its been in use for significant period is a lot better than most I've seen.

It could be asphaltenes or dead bug ... depending on the additive and fuel composition - dead bug is not always a Gel like deposit .. it can be anything from light brown gel like - to black crud ...

Basic flush out of tank ... filter the fuel - treat and put back ... new fuel filter and be happy !

 

[Farmer Piles]

As I understand, the fuel we burn on the roads does get treated but the treatment only lasts about three weeks. The key difference between cars and trucks and boat is the turnover of fuel.. Cars are topped up weekly or monthly year round with fresh fuel, trucks daily. Boats do 50 engine hours over six months of a given year and then stand idle. Moist air being drawn into the tank vents when on the water will precipitate condensation and diesel bug.
My understanding of at least part of the problem and the difference between vehicles and boats.

 

[Sandy]

As I understand, the fuel we burn on the roads does get treated but the treatment only lasts about three weeks.

Anybody got any references to support this understanding?

 

[Refueler]

As I understand, the fuel we burn on the roads does get treated but the treatment only lasts about three weeks. The key difference between cars and trucks and boat is the turnover of fuel.. Cars are topped up weekly or monthly year round with fresh fuel, trucks daily. Boats do 50 engine hours over six months of a given year and then stand idle. Moist air being drawn into the tank vents when on the water will precipitate condensation and diesel bug.
My understanding of at least part of the problem and the difference between vehicles and boats.

Sorry - not true .... additive stays effective for a long period ... longer than most would have fuel standing. Would like to know where you got such misinformation from.

Its not the additive that fails due age - it can be that initial dosing is insufficient and you only partly kill off bug ... then over a period - remaining bug overwhelms the inadequate dosing. Its why dosage charts show a high does rate as initial and then a much lower rate for maintenance.

But it is true about the 'turnover' in truck / car / vehicle tanks ....

 

[Refueler]

Anybody got any references to support this understanding?

I'd like to see as well ...

 

[Jerbro]

I'd like to see as well ...

Did anyone see the article in last Novembers PBO? It freaked me out a bit to be honest.. with quotes like “Manufacturers agree that modern diesel shouldn’t be stored longer than 6 months… and that’s including the 2 months it takes to get from the refinery to your marina pump”. I know you gotta take mag articles with a pinch of salt as a product-push might be in there somewhere (marine 16 or diesel dipper).. Anyway, I went out and bought a pack of 24 filters just in case!

How should I look after my fuel to beat diesel bug? - Practical Boat Owner

 

[Bandit]

Most boat fuel tanks are not built with a sump and a stripping ability to remove water, crud etc. Over the years water and general crud build up and eventually reach the level of the pickup line and cause problems. As I said a dirty tank that needs, treating, cleaning and the remaining fuel polished or dumped. If it is a small amount of fuel, dumping is often the more cost effective, and a commercially certain result.

 

[B27]

Glad i ran down the tank at the end of last season.
The weather has delayed our first outing, I will remove some fuel and any water from the bottom of the tank with a Pela before changing the filters.

In the past I've taken dirty fuel home and allowed it to settle.
You can often recover a lot of it, but how much do you want to faff with a quid's worth of dubious fuel?
Any fuel that might be degraded I will keep for running a Chinaspacher in the workshop, cleaning bike chains and the like.

 

[thinwater]

As I understand, the fuel we burn on the roads does get treated but the treatment only lasts about three weeks. The key difference between cars and trucks and boat is the turnover of fuel.. Cars are topped up weekly or monthly year round with fresh fuel, trucks daily. Boats do 50 engine hours over six months of a given year and then stand idle. Moist air being drawn into the tank vents when on the water will precipitate condensation and diesel bug.
My understanding of at least part of the problem and the difference between vehicles and boats.

The three week think is fiction (I was in the fuels refining business). Yes, speed of use and condensation are issues.

But that would only explain bug, not other types of sludge.

In fact, if you store diesel in glass, even wit ht he top open, it will never generate sludge unless infected with bug and contaminated with water. The sludge you see is the result of interaction between the metals in the tank and fuel system, catalyzing reactions that form sludge. Steel refinery or bulk storage tanks won't do it, because the metals involved are copper and zinc.

A little light reading:

---

ASTM D975 Appendix X2.7.2: Fuel Storage Conditions
Copper and copper-containing alloys should be avoided. Copper can promote fuel degradation and may produce mercaptide gels. Zinc coatings can react with water or organic acids to form gels which rapidly clog filters.

Cat installation guidance.
http://pdf.cat.com/cda/files/3375312/7/Diesel+Fuel+Diesel+Fuel+Systems+LEBW4976-04.pdf

Material. Black iron pipe is best suited for diesel fuel lines. Steel or cast iron valves and fittings are preferred.

CAUTION: Copper and zinc, either in the form of plating or as a major alloying component, should not be used with diesel fuels. Zinc is unstable in the presence of sulfur, particularly if moisture is present in the fuel. The sludge formed by chemical action is extremely harmful to the engine’s internal components.

Cummins installation guidance.
https://www.cumminspower.com/www/literature/applicationmanuals/t-030_p115-132.pdf

Diesel Fuel Piping. Diesel fuel lines should be constructed from black iron pipe. Cast iron and aluminum pipe and fittings must not be used because they are porous and can leak fuel. Galvanized fuel lines, fittings, and tanks must not be used because the galvanized coating is attacked by the sulfuric acid that forms when the sulfur in the fuel combines with tank condensate, resulting in debris that can clog fuel pumps and filters. Copper lines should not be used because fuel polymerizes (thickens) in copper tubing during long periods of disuse and can clog fuel injectors. Also, copper lines are less rugged than black iron, and thus more susceptible to damage.

Note: Never use galvanized or copper fuel lines, fittings or fuel tanks. Condensation in the tank and lines combines with the sulfur in the diesel fuel to produce sulfuric acid. The molecular structure of the copper or galvanized lines or tanks reacts with the acid

and contaminates the fuel.

Yanmar manual
Marine Engine Distributor | Mack Boring & Parts Co.
piping is specified as rubber or steel (page 9).

 

[Refueler]

The ASTM gui8delines were brought in not because of storage tanks - but for the sample containers that started to appear and were causing adverse analysis results when retention samples were tested some time later.
It took years to get Industry Guidelines amended to allow plastic containers - that was because of the possible vapour porosity.

Diesel fuel has a storage life far exceeeding anything yotties will do !!

Pal of mine had left his diesel Grand Tourer van standing over 3 years .... never touched ... tyres cracked / flat .. doors stuck - but we managed to get brakes released .. doors open .. jumped a battery to her ... turned the key and she started up as if she'd been parked day before.

 

[vyv_cox]

Pal of mine had left his diesel Grand Tourer van standing over 3 years .... never touched ... tyres cracked / flat .. doors stuck - but we managed to get brakes released .. doors open .. jumped a battery to her ... turned the key and she started up as if she'd been parked day before.

My boat stood for three years due to covid. Tank was about 3/4 full. Engine started within 10 seconds of turning over and used all that tank without a problem. No fuel treatment.

Incidentally the batteries, totally disconnected from themselves and the boat, showed 12.4 volts and turned the engine over fine.