Everything I Ever Wanted to Know About Diesel Fuel

[skipmac]

OK. Current stage of the refit is the fuel system which is spinning off into several sub projects and related questions. I guess I could make a different thread for each but being basically lazy decided to lump them all together.

The tanks

Aluminum, 2 X 40 gallon. Both have developed pinhole leaks in the lowest point due to corrosion from the inside. My understanding is grunge in the fuel creates an acidic something that eats through the metal. So I cut away metal until I got to clean and clear to have a new section welded on. BUT with a 6X12 hole in the bottom the inside didn't look as clean as it did peering through a little inspection hole in the top so decided to have them steam cleaned. So that leads to

Q1. How clean is a steam cleaned tank? I took it to a local shop to have it cleaned. Got it home and the inside is still black and stained. I can clearly see a line where the high fill point stops and the clean metal around the top starts. I went in with a rag and solvent and also hit it with a pressure washer and nothing comes off. However I can get a coarse scrubber or some 400 grit sandpaper and polish it back to shiny metal. So should I take it back or have it cleaned better or is the remaining stain normal and will not cause problems when its refilled with diesel?

Future maintenance.

Goal of course is to keep the fuel and tanks clean in the future so I don't have to do all this again or at least not for a long, long time. First I've read the various threads and recommendations for various bug killers so no need to But a couple of articles I read recently indicate a more serious concern is a breakdown of the fuel itself producing asphaltenes, mainly due to lower quality of today's diesel. So that leads to

Q2. Does bacteria in diesel cause/promote/contribute to the fuel breakdown?

Q3. Do the bug killers address this or is there a separate product that does? Maybe the answer is just don't let your fuel sit and get old?

Q4. Polishing. Is that anything more than running the fuel through a good filter? Can I do the same thing with a Racor and a small pump? With two tanks it would be very easy to run tank 1 empty, then clean and dry tank 1 and pump fuel from tank 2 through a filter into tank 1 then clean and dry tank 2.

I think that covers the main questions for but I'll probably remember a couple of more about a pico-second after I post this.

Any other comments, suggestions, ideas and thread drift welcome.

[bobconnie]

The first thing I would do is install a drain in the lowest point of the tank if ya can ! just keeping any water or junk off the bottom of the tank will cure many of the problems found with the storage of diesel ! it's simple and it works ! as far as to days diesel is concerned, it's no where as good as it was 10 yrs ago, but it's what ya have to put up with in the USA today ! I always look forward to getting fuel in central and south america !! Not just cheaper but better running !! just my 2 cents

[skipmac]

Originally Posted by bobconnie

The first thing I would do is install a drain in the lowest point of the tank if ya can ! just keeping any water or junk off the bottom of the tank will cure many of the problems found with the storage of diesel ! it's simple and it works ! as far as to days diesel is concerned, it's no where as good as it was 10 yrs ago, but it's what ya have to put up with in the USA today ! I always look forward to getting fuel in central and south america !! Not just cheaper but better running !! just my 2 cents

That idea is already on the radar. However I think the rules and regulations strongly discourage holes and fittings in the bottom of a fuel tank. Not that I always adhere to the rules and regulations but in this case I do see the logic. Any problems with the drain or screw-up due to operator error would result in the entire contents of the tank dumping into the bilge.

What I have done with these tanks in the past is insert a hose through the inspection plate on top down to the lowest part of the tank to suck out all the water and grunge with a small pump. More trouble than a drain but it seems to do the job and I sleep better at night knowing my fuel is safely contained in it's little tank (at least until the tank itself springs a leak ).

Thanks
Skip

[sailorboy1]

With all the time, trouble and money you have spent on that boat refit I sure hope you have just considered getting rid of those aluminum tanks to start with! Even if it met losing some tank capacity, if it were me I would be looking at replacement poly tanks!

[JPA Cate]

We used to have an aluminum fuel tank, in a different boat, and it, too, developed a pinhole leak after about 15 yrs., near the forward outboard bottom corner. Jim "field repaired it" by using tin snips to cut a piece of aluminum beer can for a patch, shaped it to the outside of the tank, and epoxied it on, like a bandaid. It stopped the leak. As far as I know, that tank is still in use, 15 years or more later, with no further repair.

[skipmac]

Originally Posted by Don Lucas

With all the time, trouble and money you have spent on that boat refit I sure hope you have just considered getting rid of those aluminum tanks to start with! Even if it met losing some tank capacity, if it were me I would be looking at replacement poly tanks!

Wow Don. How nice of you to volunteer to buy me new tanks. Is this my valentine day present.

Well, here's the deal. Except for an area less than 1 sq ft in the sump of the tank the metal looks fine inside and out. So I did the math. New tanks including shipping at least $1600-$1700 plus a few hours or more to install unless I can get custom tanks to match the exact configuration of the existing fittings (even more money). Steam clean and patch the old tanks $200. If I decide to replace them in the future it's 15-20 minutea each to pull them out again (bet you can't pull the tanks out of your boat in 20 mins ) and I've lost only the $200.

So for that I'll give the old tanks a new lease on life. Besides, after all the hauling and cleaning and welding I've kinda grown attached to them.

[skipmac]

Originally Posted by Ann T. Cate

We used to have an aluminum fuel tank, in a different boat, and it, too, developed a pinhole leak after about 15 yrs., near the forward outboard bottom corner. Jim "field repaired it" by using tin snips to cut a piece of aluminum beer can for a patch, shaped it to the outside of the tank, and epoxied it on, like a bandaid. It stopped the leak. As far as I know, that tank is still in use, 15 years or more later, with no further repair.

Thanks Ann,

I would be tempted to do a field repair (did it on a car gas tank once with similar good results) but since I'm hauled and have the time I figured do the weld. Why not live high on the hog while I can.

My big question is the cleaning. I had the tank steam cleaned but the inside is still black except on the top of the tank. I pressure washed and scrubbed the black and it did not come off so I'm thinking this is more a stain than a dried on coating of diesel grunge. So unless an "expert" tells me that this stain will grow into a new, thick coating of grunge within days of refilling the tank I think I'm going to weld on the patch and stick it back in the boat.

[sailorboy1]

Originally Posted by skipmac

Wow Don. How nice of you to volunteer to buy me new tanks. Is this my valentine day present.

I could probably manage to sit in a deck chair while drinking a beer and provide various encouragement comments.

. If I decide to replace them in the future it's 15-20 minutes each to pull them out again (bet you can't pull the tanks out of your boat in 20 mins ) and I've lost only the $200.

Would probably take me at least an hour! Half that would be to drop the dinghy and take stiff out of the stern locker to get to it. But then since my tanks are corrosion free poly I don't expect to have to. PLUS there is no such thing on a boat that only takes 15-20 minutes to do!

So for that I'll give the old tanks a new lease on life. Besides, after all the hauling and cleaning and welding I've kinda grown attached to them.

Are you positive that the tanks corroded from the inside and not from having seawater related corrosion?

Back to your original list; all bad things in diesel tanks start with water. But yes you can treat for the biological and you can add corrosion treatment to them. The biocide is easy for the most part as you can add on a regular schedule. But the corrosion issue is going to need fuel testing to know f it has gone bad.

PS - you have 1.5 months to get your boat in the water to meet your boost of getting into the water before me this year!

[Panope]

PRO-SEAL TYPE TANK SEALANTS from Aircraft Spruce

This sealant is used heavily in the aviation world (mil spec.) to create fuel tanks using riveted sheet aluminum (wings). It is designed to be used on the inside of the tank. The stuff is amazingly sticky, flexible when cured and tough. If you have good access to the pinhole area it will fix your problem.

Also, If your pinholes are confined to welds only, you could coat all of your welds as a preventative measure.

Steve

[skipmac]

Originally Posted by Don Lucas

Are you positive that the tanks corroded from the inside and not from having seawater related corrosion?

Absolutely. Inspected them very carefully on the outside when I pinpointed (pun intended) the leak. The exterior surface was smooth, clean and bright. Cut the piece out of the tank, polished the inside surface and the corroded spots were obvious. Isolated areas that look like someone put a drops of acid in a few little spots. Looked at the whole area with a 30 power magnifier and could see pitting all across the surface but except for the few spots they were very tiny pits.

Back to your original list; all bad things in diesel tanks start with water. But yes you can treat for the biological and you can add corrosion treatment to them. The biocide is easy for the most part as you can add on a regular schedule. But the corrosion issue is going to need fuel testing to know f it has gone bad.

As I get further into this one part of the plan for the future is to keep not let fuel sit in the tanks for long periods. I may even put in a small day tank for putzing around and not fill the main tanks until I'm ready to go somewhere.

PS - you have 1.5 months to get your boat in the water to meet your boost of getting into the water before me this year!

PPS
I'm pedaling as fast as I can. If I wasn't dealing with some yahoo from MA I would be on the way out to the boat right now.

[skipmac]

Originally Posted by Panope

PRO-SEAL TYPE TANK SEALANTS from Aircraft Spruce

This sealant is used heavily in the aviation world (mil spec.) to create fuel tanks using riveted sheet aluminum (wings). It is designed to be used on the inside of the tank. The stuff is amazingly sticky, flexible when cured and tough. If you have good access to the pinhole area it will fix your problem.

Also, If your pinholes are confined to welds only, you could coat all of your welds as a preventative measure.

Steve

Thanks for the info but too late for this job. Already cut holes in the tanks. Really wanted to do that anyway so I could look closely at the metal to see how bad it was. Serious, widespread corrosion I would have replaced the tanks. Since it was localized just in the bottom I decided repair time.

Next step I need to decide what I'll do about the black staining.

[sailorboy1]

Originally Posted by skipmac

PPS
I'm pedaling as fast as I can. If I wasn't dealing with some yahoo from MA I would be on the way out to the boat right now.

Must be someone else as I'm not from MA!

I have customers who still have boiler fuel oil that has been in tanks for years and it is still good. I feel the only problem will diesel in tanks a long time is if they get contaminated and then just sit. I don't think day tanks are an answer except you can filter from the main tank to reduce engine problems. But this does nothing far as aluminum corrosion.

[Jim Cate]

G'Day Skip,

On the issue of the black deposit: Try rubbing briskly with a clean rag dipped in diesel oil. IF nothing comes off on the rag, it is likely that the deposit will not harm stored diesel.

And re the drain in the bottom question: A well engineered drain seems mo more likely to fail than the bottom of the tank itself (via corrosion that would perhaps be eliminated by the drain's action!). IF it were my boat, and the drain could be accessed so easily that frequent checking would be likely, I'd put one in.

One of our fuel tanks is the steel fin keel that is bolted to the bottom of our strip planked vessel. I have considered putting a drain into it, to be used when on the hard. Haven't gotten around to it as yet, but if we need to sand blast and recoat the keel I think that I will do so. Would be nice to have the option of really emptying that container completely.

Cheers,

Jim

[skipmac]

Originally Posted by Don Lucas

Must be someone else as I'm not from MA!

Oh that's right. Forgot. Just your boat is from MA. The owner is from some small, obscure place in the nether reaches of New England. Something like the western suburbs of Maine.

Originally Posted by Don Lucas

I have customers who still have boiler fuel oil that has been in tanks for years and it is still good. I feel the only problem will diesel in tanks a long time is if they get contaminated and then just sit. I don't think day tanks are an answer except you can filter from the main tank to reduce engine problems. But this does nothing far as aluminum corrosion.

The idea of the day tank was to keep the main tanks empty and only put fuel in them when I will be using it in the near future.

I'm guessing the PO didn't stay on top of keeping the tanks clean and dry so maybe a little closer attention to that will prevent a re-occurrence.

[skipmac]

Originally Posted by Jim Cate

G'Day Skip,

On the issue of the black deposit: Try rubbing briskly with a clean rag dipped in diesel oil. IF nothing comes off on the rag, it is likely that the deposit will not harm stored diesel.

And re the drain in the bottom question: A well engineered drain seems mo more likely to fail than the bottom of the tank itself (via corrosion that would perhaps be eliminated by the drain's action!). IF it were my boat, and the drain could be accessed so easily that frequent checking would be likely, I'd put one in.

One of our fuel tanks is the steel fin keel that is bolted to the bottom of our strip planked vessel. I have considered putting a drain into it, to be used when on the hard. Haven't gotten around to it as yet, but if we need to sand blast and recoat the keel I think that I will do so. Would be nice to have the option of really emptying that container completely.

Cheers,

Jim

Hi Jim,

Where my tank is installed the bottom corner is inaccessible so if I installed a drain there I would have to connect hose or line to run to a spot in the bilge where I could reach it to drain the tank. I'm not concerned so much about the fitting itself failing but the stuff attached to the fitting.

Excellent suggestion about the fuel and a rag. I did try some mineral spirits and a rag which didn't do anything. No diesel at the house where I have the tank but I'll bet I can get some at the local Shell station and will give that a go.

Regarding the drain in your bilge tank, I have a sump in my bilge under the water tank that I can't reach. I did drill a hole in the keel and install a drain for that to keep the bilge dry while I'm on the hard. Love it.

Thanks
Skip