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wind cree 06-10-2019 08:40 AM

Black Sludge
 
I just changed the fuel filters in my Yanmar 2GM20F. The Raycor filter had a slight layer of black gook in the bottom of the plastic bowl screwed on the bottom. Nothing appears to be floating in the fuel itself. And the secondary filter looked clean in the bowl. It's been just over a year since the last time I changed the filter. Am I looking at a bad fuel tank?? Is there a such thing as cleaning a fuel tank? The motor works perfect and always starts and runs so pretty sure it's not made it into the injectors.
As always any suggestions greatly appreciated.

capta 06-10-2019 10:34 AM

Re: Black Sludge
 
Depending on its size and access to the interior, cleaning a fuel tank can be an expensive worthwhile or worthless experience. Most tanks have baffles which limit the amount of cleaning that can be accomplished without making holes in the tank to clean behind the baffles.
We have dirty fuel tanks (38 years old) and we keep lots of filters aboard and change them frequently. If you don't already have a Racor 500 as your primary, chuck what you have and install one of those with or without the gauge.
Then just change the filter frequently and you'll not have to worry. The nice thing about the Racor is that you change the filter from the top, so you don't have to make a mess of your bilge.
Many will try and suggest a fuel polishing system, but your diesel does that anyway so unless you are starting out with a perfectly clean tank, they aren't really going to make a whole lot of difference. Fuel polishing doesn't clean what's growing on the sides and top of the tank. A fuel polishing only cleans out whatever is suspended in the fuel, just as the return system on your engine does.

Minnewaska 06-10-2019 10:46 AM

Re: Black Sludge
 
If you have black sludge in the bottom of the primary, it's most likely dead bacteria that live in diesel. Especially, if there is high moisture or water in the diesel.

I used USA Fuel Service to clean my tanks. Not sure where you are or if they have anyone close. It would appear you do need to clean your tanks. They pump out all the old fuel first, then polish it to remove impurities. Then they spray solvents into you tank through whatever access they can find. They used the fuel level sender in my case. They pump out the solvents and debris, then put the polished fuel back.

Uncle Bob the 1st 06-11-2019 04:53 AM

Re: Black Sludge
 
Quote:

Originally Posted by Minnewaska (Post 2051607746)
If you have black sludge in the bottom of the primary, it's most likely dead bacteria that live in diesel. Especially, if there is high moisture or water in the diesel.

I used USA Fuel Service to clean my tanks. Not sure where you are or if they have anyone close. It would appear you do need to clean your tanks. They pump out all the old fuel first, then polish it to remove impurities. Then they spray solvents into you tank through whatever access they can find. They used the fuel level sender in my case. They pump out the solvents and debris, then put the polished fuel back.

Hi i have found that the black "sludge" can sometimes be asphaltenes that appear as a sludge however when closely examined they appear as little black balls that clog the fuel system. If you can get some of the black sludge out into a small container, place some in the palm of your hand and add some metho and rub, if it dissolves into a blackish brown paste you have asphaltenes. Polishing the fuel through a 30 micron filter worked for me.

mbianka 06-11-2019 07:28 AM

Re: Black Sludge
 
Quote:

Originally Posted by wind cree (Post 2051607702)
I just changed the fuel filters in my Yanmar 2GM20F. The Raycor filter had a slight layer of black gook in the bottom of the plastic bowl screwed on the bottom. Nothing appears to be floating in the fuel itself. And the secondary filter looked clean in the bowl. It's been just over a year since the last time I changed the filter. Am I looking at a bad fuel tank?? Is there a such thing as cleaning a fuel tank? The motor works perfect and always starts and runs so pretty sure it's not made it into the injectors.
As always any suggestions greatly appreciated.

When I converted my boat from diesel to Electric propulsion I decided to use the old diesel fuel tank as a fresh water wash-down tank. I was amazed at what I discovered when I began to clean out the old diesel tank. You can see what I found at and how I cleaned out the tank at this blog post:
https://biankablog.blogspot.com/2011...-of-grime.html

krisscross 06-11-2019 03:37 PM

Re: Black Sludge
 
Had my tank professionally cleaned out before I left for the trip from Pensacola Florida to North Carolina. They pulled over 3 gallons of water out of about 30 gallons of fuel, as well as some black solids that are bacterial in nature. Well worth it in my opinion.

MarkofSeaLife 06-11-2019 03:45 PM

Re: Black Sludge
 
When I had a fuel problem I had a mate come over and he happened to have a fuel transfer kit and a polisher. So we sucked out all the fuel & whacked in ferry cans and polished it.

We then squirted a ferry of clean diesel around the inside of the tank and sucked it out again.

Nice clean tank. Not pristine, but clean enough.

Pretty easy to do with the fuel transfer pump and polisher.


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