Old Diesel Fuel in Tanks - burn it up or clean it out?

[richardoren]

Hi Guys,

Off to the old boat this weekend with the family as elves. While down there it seems timely to address the fuel tank issue. The boat was left relatively unattended for quite a few years. Both tanks are full and diesel here costs $7/gal so I prefer to use it rather than scrap it but don't want any fuel problems while in the middle of the sea.

Should I dump it, have the tanks cleaned, and then refuel? Or do the DDs pretty much polish old fuel by cycling it back, as I've read in the threads here?

I bought a bunch of Diesel Klean and Pri-D as additives, but didn't use them yet. Sure hope the later solution and a few quarts of magical miracle goop can do the job.

Cheers,

Richard

[REBrueckner]

Without a doubt the premium approach is to empty the tanks and have them cleaned...it's also an expensive option. Was the boat stored in Vermont? Fuel generally stores better in northern rather than southern climates so that's on your side

Check your primary and secondary engine filters and see what they look like...change filters and clean bowl contents has required. Ditto for any genny. Have extra filters aboard. Likely a good idea to use 20 microns in your RACOR types to start. Watch them closely during the first few cycles of operation.

I'd stick a hose down each tank fill and pump a gallon into a pail to see what each looks like. A cheap drill pump is good enough for this. If you can, push the hose to the very bottom of the tank and pump again...see if you pick up much crud. You can also puchase sticky stuff and stick the tanks...water at the tank bottom will cause the color to change.

Have the engines been run recently using the fuel in the tanks? If so likely they'll be ok and monitoring fresh filters should be ok. Or you can try running the genny first if that hasn't been...that's a way to test fuel also.

Maybe someone can post how you have diesel fuel analyzed...like lube oil. I think many lube oil analysis labs also will do diesel fuel.

Ah, the joys of used boat ownership...

[MikeP]

I discovered that there was 100 gallons of fuel in a forward waste tank (converted to fuel by the original owner in 1980) in our 53MY. The PO had unconverted the fwd tank but all he really did was remove the fuel connections. When he did so, he didn't realize (or later forgot) that the fwd tank was still full of diesel. This was in 1998. In 2004 we bought the boat and discovered the full tank of fuel.

I opened the top fitting, drew some diesel out from close to the bottom - it looked fine. Then I performed an extremely scientific test - I burned some! Yep, I drew off a bit of fresh fuel from the main tanks, dipped a rag in and lit it. Then I did the same with the old diesel. Both burned in exactly the same way - same color flame, same color smoke, no crackling sounds that might indicate water. So I pumped the Fwd tanks 100 gal of 6 year old diesel into the main tank and it was perfectly fine.

Admittedly, it was then mixed with newer fuel so that helped ensure it wouldn't cause a problem.

Do you have priming pumps? Depending on how they are set up, they can act as fuel polishers. If it was me I'd just add some cetane improver and maybe a bit of biocide and run the priming pumps for a couple of hours then fire up the engines - with, as Reb said, having several spare filters handy!

If you don't have priming pumps or don't have them set up so as to be able to also polish, I'd do the same thing additive-wise and just crank up the engines. DDs "polish" most of the fuel that goes into the fuel system as they are running anyway since they return a large percentage to the tank.

You might also consider adding as much new diesel as possible to the tanks once you determine that the old stuff will run the engines. I'm comfortable that my "fire" test will determine that but, of course, the usual cautions apply.

Dumping the diesel would be the last resort if the stuff just won't burn!

[Mike36c]

$7 gal? Burn it! You WILL foul filters so bring lots of them and changing them in a hot engine room at sea is no fun. Maybe install a cheap fuel priming pump if she doesn't have one already.

[krush]

In my experience, diesel fuel doesn't "go bad" it just can get contaminated.

[Nonchalant1]

When we bought our boat, the PO had run both engines off the forward tank for years, and the aft tank was full of old fuel. I have no idea why. I set it up to run with one engine off each tank and took off on a 1,200 mile trip home. As soon as we got into 3 ft. waves, it stirred up all the crud in the tank and stopped my port engine in the middle of Lake Erie due to a totally plugged RACOR. I changed RACORs frequently and just burned the old fuel. I never had to change the final fuel filters that trip (I do that annually or 500 miles). We've been 8,000 miles since then with no problems and RACORs last a long time now.

DDs do use extra fuel to cool the injectors and return a lot of filtered fuel to the tanks every time you run. Unless you have a lot of water in the tanks, just run it and bring plenty of RACORs and 2 spare final fuel filters per engine. Use 30 micron RACORs and the DD recommended (3 micron?) final filters. You can get those vacuum gauges for your RACORs to monitor their condition (just replaces the T-handle for the top). The final filters tell you when they're getting plugged up by that engine not running at full speed any more, even with a new RACOR.

Doug Shuman

[REBrueckner]

Reportedly, partially clogged RACORS will enable an engine to run smoothly but not properly cool and lubricate injectors which significantly shortens injector life. To combat this, the best approach is to use vacuum gauges on RACORS and as vacuum climbs change filters before an engine begins to slow down or run irregularly.

Although RACOR kits mention fifteen feet (if I recall correctly) between helm gauge and filter at the other end, I used about 25 feet of copper tubing with hose clamped on either end. Maybe 25 feet of hose would work also but I had a narrow crevice to get through and the thicker hose would not fit.

[Brian Degulis]

I would suck some fuel off the bottom of the tank if any water is present keep pumping untill it free of water. Then I would use that same tube with a pump (a fast pump around a gallon a minute) draw fuel off the bottom thru a filter. (not a spin on a Racor with a plastic bowl so you can see whats going on and also see the element) and return it to the tank. Run that for a full day then check the element.

You will acomplish 2 things you will get some of the crude out and you will see just how fast your going to go thru elements. Granted the boats not moving and stirring the tank but it will give you an idea.

Then I would treat the fuel with an enzym like startron and a cetane booster or Diesel Kleen. If there was water in the fuel I would also use a dispersant just this one time. Some disagree with that and say you must get all the water out. I believe sometimes that's just not possible and water in the bottom of the tank will give you problems down the road. If you did get all the water out then the dispersant does nothing and does no real harm. But if by chance some still remains you will get rid of it and prevent future problems. But do it only for this one load of fuel and only if you know you had water in it Good Luck.

Brian

[nyrussell]

Get some AJX both systems, follow the directions and you should be fine, Had a problem with old diesel and main tank until I added it. This solved the problem, Have to get some for the other tank which we never used and who knows how old it is...

Noel

[spartonboat1]

I recommended locating a good diesel tech with fuel polishing gear who would come to the boat and run his (her?- have yet to meet my first female diesel tech, no disrespect intended- and that cover about a 50 year period) fuel polishing equipment. I am familiar with at least two situations where that has been necessary, 3rd hand, and I have 1st hand knowledge of the tech and capabilities.