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Cleaning out gas tank at home

I've had my car up on jacks for about a year now while I wait for Ollie's to get my engine parts back to me.

I've realized that I should probably empty out the gas in my tank, as it's been sitting in there for a year now... and it will still be months away (I HOPE!!) until I get my engine rebuilt and put back in the car.

I'm guessing I can drain it from the bolt located underneath... but is there something I can use to flush out any crud that has settled in the tank? I don't want to start up a new rebuild with a dirty fuel tank.
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Old 08-11-2018, 01:28 PM
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Track, that big Allen socket drain plug has a sock filter attached to it. When I did the same thing you're about to do, I had a new filter ready - and used it - but I needn't have; the original was not clogged and was easily cleaned.

Maybe take a peek into the tank through the hole where the level sensor is mounted; you may well find that it's pretty clan inside. Or not. But if it is, which is how mine was, I'd suggest that "less is more" in terms of how you proceed. I also stripped and refinished the outside of my tank, which was good because there was some corrosion just starting at the flange where the two halves of the tank are joined. In fact I'd chance a guess that it's usually the exterior of our gas tanks that need more work, but I could be wrong on that. Best regards, John
Old 08-11-2018, 02:56 PM
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Did you have any Stabil in there? If you did, not sure I would be in any rush to drain. I'd wait until the engine is back together and you can refill with fresh fuel as soon as you drain the tank.

If you must drain, first take out the fuel sender and siphon most of the fuel out from above. I siphon the fuel into DOT-approved fuel jugs, since you'll likely have it around a while until you can dispose of it at your haz waste day, or you can gradually burn it in your daily driver. This will also let you eyeball the inside so you can tell whether or not you have any crud.

Only then would I remove the bolt/strainer from underneath. Even with most of the fuel out, make sure you have something large to capture the spray of fuel that comes out. I like the large, plastic mortar beds you can get at Home Depot for things like this.

Wouldn't hurt to have a fire extinguisher around either.

Mark
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Old 08-11-2018, 03:00 PM
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Can anyone tell us if these gas tanks are raw steel on the inside or are they (something like) electroplated or galvanized internally? Thanks, John
Old 08-11-2018, 03:05 PM
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Mine in my 77 was raw steel. I drained it then pulled the sending unit then attached a rag to a coat hanger put it though the sending unit hole and wiped the bottom clean with it. You can then let it dry and if you are anal you can shop vac it out through the sending unit with a smaller hose to be sure nothing is left if anything is sitting around in there.
Old 08-11-2018, 04:57 PM
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I recently pulled a tank on a car that was giving me problems. Plugged all the holes and several gallons of white cleaning vinegar shaking and turning over several days then draining and rinsing with distilled water. Surprise what thirty five years produces.
It took a long time for grass to grow where I poured it out.
Bruce

Last edited by Flat6pac; 08-11-2018 at 05:44 PM..
Old 08-11-2018, 05:42 PM
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Did you have any Stabil in there? If you did, not sure I would be in any rush to drain. I'd wait until the engine is back together and you can refill with fresh fuel as soon as you drain the tank.

Mark
Thanks... I DID put some Stabil in there about 8 months ago... but even Stabil says that they don't recommend running gas that's been sitting for over a year.


Most likely I won't have my engine back in until sometime next year... (still waiting on Ollie's)

I guess I'll just drain it and then take a look inside. I wish I had a pic of what a clean tank looks like on the inside to compare it with.
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Old 08-15-2018, 01:09 PM
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I'm in a similar boat, my tank has been empty for 8 years now. Need to pull the fuel sender off the top and have a look inside. Have new fuel lines to run up through the tunnel while the powertrain is out and the shifter is off (e-brake has been long gone). Maybe use a sprayer nozzle and spray some fresh fuel around the walls of the tank to rinse the walls off, then drain.
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Old 08-15-2018, 02:26 PM
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Quote:
Originally Posted by Trakrat View Post
I've had my car up on jacks for about a year now while I wait for Ollie's to get my engine parts back to me.

I've realized that I should probably empty out the gas in my tank, as it's been sitting in there for a year now... and it will still be months away (I HOPE!!) until I get my engine rebuilt and put back in the car.

I'm guessing I can drain it from the bolt located underneath... but is there something I can use to flush out any crud that has settled in the tank? I don't want to start up a new rebuild with a dirty fuel tank.
If you pull the tank, POR 15 makes a product called Marine Clean, which is excellent for cleaning tanks right down to the metal.
Old 08-15-2018, 02:29 PM
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I suggest the fuel sender location on top as well. Gives you a direct look into the tank to see what it looks like in there. I bet you'll be pleasantly surprised to see it's quite clean in there.

It's very easy to remove the nuts and then wiggle the sender out of the hole. Also gives you the opportunity to replace the old rubber gasket that's sealing the sender to the tank.

Once you get the sender out, you can human siphon out the fuel with a simple hose (the taste of sex panther/pure gasoline is fantastic by the way......) or pump it out with a remote fuel pump. You can also use the pump in the car to pump it out? Look on the wiring diagram to see which fuse serves it in the panel and feed it 12v there?

I've always done it with a remote pump because I have a number of spare Holley fuel pumps from my crappy racecar fuel system. I can send you one for nothing, including some hoses with fittings if you want it.
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Old 08-15-2018, 03:35 PM
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I see Stoddard sells a tank sealing solution (generic I assume) and wonder if that would be a good idea if you're going to the hassle of cleaning etc. Especially with the da**ed ethanol crap we have to use...
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Old 08-15-2018, 03:42 PM
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Remove the sender and use your camera phone. You can put the phone right up against the hole as it has a built in flash. I got some pretty good views and decided that the tank and the filter in the pot was clean enough.


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Old 08-15-2018, 06:18 PM
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I have used 2 different types of petrol tank restoration kits.
One was POR15 and the other was KBS auto fuel tank sealer kit.
Basically they involve rinsing out the tank, then washing with a degreaser.
Once clean, rinse through an etching product making sure that all surfaces are always wet with product and finally circulating the sealant around the tank and leaving it to set.

After I did it the first time, I swore I'd never do it again. But I did. both to two old VW fuel tanks. I could see all the rust had been eaten away by the etching process and then it was sealed with the sealant. The inside of the tank looks brand new afterwards. Your outside of your tank might not look so good if you're clumsy like me. So leave any outside painting until last.
I've sealed the tanks about 3 years ago now and had never had any issues.

If you're going to do it though, make sure you do it in cool weather. It's HARD work tumbling the tank over and over and swirling it around for as long as you're supposed to. The end result is great though. Costs about $100 AUD. I imagine less in the US.
Old 08-15-2018, 09:00 PM
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what size is the hex on this screen at the bottom of the tank?

Thanks

David
Old 10-28-2018, 04:55 PM
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if it is the least bit questionable I would consider one of the dansk reproduction units. they are surprisingly affordable in the grand scheme of things at around $700. I paid another $200 beyond that for a dansk reproduction oil tank.


if it looks clean drain it, fill the lawn mover with the left over fuel and carry on.
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Old 10-28-2018, 05:49 PM
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what size is the hex on this screen at the bottom of the tank?

Thanks

David
It's 22mm, but you don't need to go get a huge hex wrench. Just go to the hardware store and buy a bolt with a 7/8" head. It will fit in the bung. Double-nut it so you can apply some torque. That's how I got mine out.

Mark
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Old 10-28-2018, 06:07 PM
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Quote:
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It's 22mm, but you don't need to go get a huge hex wrench. Just go to the hardware store and buy a bolt with a 7/8" head. It will fit in the bung. Double-nut it so you can apply some torque. That's how I got mine out.

Mark
But before you spend money at the hardware store, look around for a generic spark plug socket that has the flats (for a wrench) around the top of it. See if the flats will fit into the hex head of the fuel tank drain plug. IF they do, then put a socket extension through the spark plug socket (opposite of normal) and use that tool with a ratchet to loosen and remove the drain plug.

IF your car has a CIS engine, then the tank will have a plastic swirl pot. You don't want to destroy the plastic swirl pot by shaking a chain or rocks or whatever in the tank to clean it, and the fuel tank sealers on the market will NOT adhere to the plastic swirl pot.
Old 10-28-2018, 06:18 PM
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I used apple cider vinegar to clean a 1976 rusted gas tank. Worked great. In a week the inside of the tank looked new.
Cheap, no harmful chemicals and great results.
Old 10-28-2018, 06:29 PM
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These photos show a tank split in half from a 1973.5T with the first CIS. The baffling and swirl pot are in all CIS cars. From the picture you posted you have the same configuration as well. The swirl pot is made of bakelite (just like the rotor or distributor cap) and certain coatings to not adhere to the bakelite, will flake off and clog that large 22 mm filter. One such coating is REDKOTE. Avoid REDKOTE!!!!!!!!

I sent my tank to a radiator shop to be "boiled". I believe they use a hot phosphoric acid bath to remove rust and scale form the inside and outside. Your left with "coat internally or not coat". POR products according to many owners who refurbished tanks does very well.

Good luck

Bob
1973.5T/CIS
Old 10-29-2018, 07:30 AM
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oops....
Old 10-29-2018, 07:31 AM
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