Black tar-like substance in diesel fuel sediment bowl

[AcreageGuy]

I have a Deere 2-cylinder 730 diesel tractor that only gets started a couple of times a year. It's been 10 years or so since I used it in the field to moldboard plow a few acres. The last two times I've tried to start it to move it around, I've found the bottom of the sediment bowl with a substantial amount of sticky black tar-like substance in it. My usual go to solvent for clean up, naptha doesn't touch the stuff. Brakleen does, and lacquer thinner is even better. There was so much of it this time, that I drained the fuel tank and looked inside, where I could see it on the bottom of the tank. I put 2.5 gallons of lacquer thinner in the tank, hoping to dissolve all of this stuff to get it out of the tank. I plan to leave it in there a week or more, hoping to get it all dissolved in the thinner before I drain it out. I rock the tractor back and forth once a day or so, to swish the thinner back and forth in the tank.

Anyone know what this stuff is? Is it something precipitating out of fuel containing biodiesel, because that's all I can find these days. Is it algae, which someone had told me years ago was only a problem in plastic fuel tanks? I looked in the tank of my restored 4020, which gets used a little more, but not a lot, and it appears to be clean.

 

[ruffdog]

Is it like asphalt? Do you have the diesel bug?

There are two major types of Diesel contamination -

Penray’s Total Diesel Fuel System Cleaner Fights Asphaltenes, Cleanses Contaminants And Deposits - Penray.

 

[AcreageGuy]

Is it like asphalt? Do you have the diesel bug?

There are two major types of Diesel contamination -

Penray’s Total Diesel Fuel System Cleaner Fights Asphaltenes, Cleanses Contaminants And Deposits - Penray.

I guess so. It's dark black, very thick in viscosity and very sticky. Takes a strong solvent to get all the residue off of the glass bowl or my fingers. I'm glad it didn't get any farther than the sediment bowl in my 730. I had never heard of asphaltenes in diesel fuel, but that must be what it is, If it takes a long time to come out of the fuel, maybe its not a problem in tractors that are used regularly? I'll have to find some of the Penray's cleaner and put some in at least my 2 old diesels that aren't used regularly.

 

[RjCorazza]

Interesting. I've seen microbial contamination, but it doesn't require solvents to clean up. I've never heard of asphaltenes, but the op's problem sure sounds like it.

 

[Wagtail]

Interesting. I've seen microbial contamination, but it doesn't require solvents to clean up. I've never heard of asphaltenes, but the op's problem sure sounds like it.

Well, I've certainly learnt something today.

 

[mcfarmall]

I've had a similar substance in the bottom of gas cans that were used with E10 but haven't seen it in my diesel cans or tractor water separator.

 

[Bavarian]

Quite likely it's crude. It comes in the fuel.
Where do you source your diesel from? It might be a filtering issue at your supplier but there is always residue present.

 

[RonF]

Hot diesel fuel will try to reverse the cracking process it went thru at the refinery. Basically you are making road tar. Small fuel tanks with low level of fuel is a cause. As unburned fuel is returned to the tank, excess heat is cooled by fuel in the tank. Keep as much fuel as possible in the tank when operating. It will keep the fuel cooler. Top off the tank at end of use. That helps eliminate water condensation. A fuel cooler can be plumbed into the fuel system. Regular use of asphatene fuel conditioner will help prevent the problem once the fuel system is cleaned of the buildup. It internally coats the system. What you see in the filter is the tip of the iceberg. Expect to change fuel filters often until everything is dissolved and flushed. A biocide along with a fuel treatment for low sulfur content should always be used as long term. Sometimes it is cheaper to rent rather than own something that is infrequently used.