How to Completely Empty A Fuel Tank?

[rardiH36]

I have just completed installing a new Moeller plastic diesel fuel tank in an vacant/unused location on my Cherubini Hunter 36.

Did this because the 38 year old OEM tank was showing first signs of leaking. The OEM tank is in a really tight location. Removal means cutting into pieces. Manuevering cutting tools into the area will be difficult. So for now (or maybe forever), I plan to leave the OEM tank in place. Empty. Never to be filled again. Probably will epoxy "weld" the fill cap so the tank can't be filled again by mistake.

Using my boat's in-line electric fuel pump, I was conveniently able to remove and transfer the contents of the OEM tank to the new one. I am sure though that just a bit of liquid fuel (and bottom sludge probably) remains in the tank... To continue to slowly leak over the next several months.

What is the best way to get the tank totally empty? I am thinking to insert a 5/8" or so hose into the fill tube. Then tape/seal the top end to the intake hose of a wet/dry shop vac. Suck it out. And hope that sparks of the vac motor don't ignite anything. Fire extinguisher at hand!

Too dangerous? Any other suggestions? I suppose poking some holes around the bottom is an alternative. But in the back of my mind, maybe an in-situ repair of the tank someday might be possible. So don't want to damage it further.

Thanks

 

[Don S/V ILLusion]

Any vacuum will work - the difficulty occurs if there are baffles in the tank.

I'd just cut it up and be rid of it. Far more trouble trying to do what you describe for no apparent reason.

 

[shemandr]

You can use one the oil extractor pumps (Mine is Moeller, I think). Put the hose down the fill hose, vent tube, engine pick up, engine return, and fuel gauge fitting, to suck out the remaining fuel. I did this with a gasoline tank I had inadvertently put water in. I was surprised how efficient that pump was. You may have to get creative to get the last bit out.
https://search.defender.com/?expression=Fuel+extractor&x=8&y=8

 

[Calif. Ted]

Please don't try the shop vac, while diesel doesn't ignite readily, when atomized and run thru an electric motor it might be a diesel flamethrower. Most pick-ups are above the bottom so you don't suck up the gunk on the bottom, 10% springs to mind, but memory fails. Try to suck it out manually as suggested, when removing large underground gas tanks, once empty it was practice to use dry ice to displace vapors with heavier CO2.

 

[dlochner]

The Moeller Oil Change pump works well. Use that. Then get a bunch of the oil absorbent pads and place under the tank and drill a hole in it to drain the rest. Cut it up and send it to the recycling center. Probably get a few bucks for the metal.

Take a look at this video:

 

[Maine Sail]

Pull the fuel gauge sender, drop a vacuum "oil extractor tube" into the very bottom and suck as much as you can. Next wrap a microfiber towel around a dowel and again going through the fuel sender absorb what you can. You can now get in there with a pump garden sparer full of undiluted degreaser (Simple Green etc.) and wash it down. Repeat the same steps above. Oh and place some oil absorbents pads and microfibers where it leaks. If the leak is under it it will be very, very difficult to get rid of the odor without cutting the tank out.

 

[Rick Webb]

If you add water the diesel will float up to where you can suck it out and dispose of properly. Do this a few times until there is only water left in the tank then forget about it.

 

[thinwater]

Oil extractor.

I've seen nasty fires started using a shop vac on diesel in industry. Diesel won't burn easily, but the mist sure will.

 

[Gunni]

Get as much oil as you can out by extractor and then add floor dry (kitty litter) to absorb what diesel is left. Buy some pelleted dry ice and add that to inert the tank atmosphere. Vent the area well with fans and start cutting. Add dry ice as needed to keep the tank "smoking".

 

[seadaddler]

Makes sense to use a oil extractor and cut hole to use rags
or paper towels get the rest and cut up and out so safe and done.
Nick

 

[py26129]

When I emptied my tank I essentially did what Mainesail recommended. In addition to his suggestions, I also used a cheapie boroscope camera from Amazon. It was small enough to go through the sender hole alongside the hose used to extract the fuel and I was able to see what was going on inside the tank.

Matt

 

[CaptKimble]

hold my beer and watch this...(turns on shop vac)

 

[Justin_NSA]

My wife can give lessons on emptying a gas tank!
She doesn't get on here

 

[shemandr]

If you add water the diesel will float up to where you can suck it out and dispose of properly. Do this a few times until there is only water left in the tank then forget about it.

I sorta did this on the tank I added water to. I'd like to add that with fuel floating on the water it is very easy to tell when you've got almost all the fuel out. I was trying to get the water out but nevertheless the line of demarcation very clear in the extractor tank.

 

[All U Get]

Sometimes I wonder about you guys, no shop-vac for fuel spills. You may not look surprised but it’s hard to tell without eyebrows.

All U Get

 

[Roadking Larry]

Best way I've found to empty a fuel tank is to be 3 gallons from home with only 2 gallons in the tank when the wind dies.

 

[Stu Jackson]

Best way I've found to empty a fuel tank is to be 3 gallons from home with only 2 gallons in the tank when the wind dies.

Aha, a man who thinks ahead.

I've run our boat without an operating fuel gauge for 20 years. Fuel consumption is the only valid way to know what ya got. Why? 'Cuz fuel pickups don't go to the bottom and for my 23 gallon tank I always plan on only 20, worst case, with a few in reserve. If I can't make it with a full tank on that 20 I seriously rethink my next passage.

5 knots, 0.5 gallons per hour, do the math.

Worked superbly on our trip from SF to BC in 2016.

I believe it is critical to know, for sure, your engine's fuel consumption.

Then, go out and have fun.

Good luck, rardi.

 

[kappykaplan]

I believe it is critical to know, for sure, your engine's fuel consumption.

 

[rardiH36]

The OP here.

Thanks all the tips/suggestions. And also the digression towards the importance of fuel level uncertainty.

Certainly the alternative of using a wet/dry vac to suck the bottom fuel/sludge out will not be attempted.

For Maine Sail: Whereas the new Moeller plastic tank has a reasonably large circular "hole" for the sender assembly, my bad OEM tank is fitted with a mechanical fuel gauge with a circular dial on the top of the tank. Wish I had a picture handy. Always was quite reliable. But from my visual memory, the hole into which it it fitted is probably 1" ... or less. Plus not easy accessed for removal. Probably won't be too useful for the microfiber towel on a dowel. But all your other steps do add up to a doable outcome. Thank you. I'll probably use Industrial Purple. That stuff in full strength has no trouble dissolving and emulsifying grease and oil. I have even used it as a paint remover substitute. (Don't ask how I accidentally discovered this feature of Industrial Purple!)

One very useful feature of the plastic Moeller tanks: I mounted my new one in a location that by chance is readily visible. After partially filling it, I realized that I didn't really need to purchase a 12V gauge and find a place to mount it. This because the plastic tank material is transparent enough the fuel level is readily seen just by looking at the tank!

 

[jssailem]

5 knots, 0.5 gallons per hour, do the math.

I tried that.. All worked well while there was fuel in the tank... Then I learned that my aged engine was getting more like .75 gallons per hour. Guess what happened to the right tank..
Yes fuel starvation...(I'm the yellow guy)

45 minutes of transferring fuel from left tank to right tank (through filters cause the left tank fuel had bugs). Wife was siting in the cockpit reading her book, charged with the horn and the responsibilities of monitoring other boat traffic (Do not let us get hit) and keeping us west of the line of nav buoys that marked the 3 ft water.
Little did I know that her book was an engaging mystery novel, a real page turner.
After about 15 minutes into the transfer I climbed back into the cockpit only to be rocked by a TOO CLOSE boat wake and the observation that we were now between 50 and 75 yards beyond the buoys. The water depth had changed from 60 feet to 10 feet and shrinking...
Jumped on the helm, turned the boat towards deeper waters, and told my Brother in Law, ( my wife's brother) stop laughing.

I now use a more conservative assumption of fuel rate.