Draining the Fuel Tank.

[jeepie]

I have a 91 auto, can I remove most of the fuel from the tank by connecting a hose to the schader (sp.) valve on the fuel rail and turning the key on and have the fuel pump empty the fuel tank ? Is this a good idea ?
I want to clean the bottom of the tank and replace the fuel pump and sock.
Thanks.

 

[c4cruiser]

Once you pull the fuel pump just use a siphon hose to drain the tank. The hole in the top of the tank is not really that big to get something in to clean it. IMHO, you would be better off by removing the tank and have it cleaned. The biggest problem is gas fumes or even some residual gasoline remaining in the tank.

There is a procedure in the service manual that calls for filling the tank with water and a cleaning solution to remove all trace of gas. This does require removal of the tank from the car, but that is not too big of a procedure. BTW, iif you are going this far, you should also change the fuel filter at the same time.

 

[Ken]

Unless you have had some really bad gasoline, or the car was sitting with gas in the tank for a prolonged (very long) period of time, there should be no need to clean the inside of the tank. The tank has a bladder, the construction of which I am unsure but it's pliable, like rubber, and nothing should stick to the tank like it would to the steel tanks. Today's gasolines don't break down into a varnish-like substance anymore unless you're talking a long, long, period of time. It used to be only a matter of months when the gasoline would go bad, and varnishes would form. Gasoline still only has a recommended shelf-life of about six to eight months at any rate.

If you do want to drain the tank, it would be a lot easier, and almost just as fast, to simply disconnect the inline fuel filter and let the gasoline drain that way. You should be able to get just about all of it that way.

As for cleaning the tank before performing any hot work on it, please keep safety always a first priority. I wonder how many people are aware that RFG can be more volatile than normal gasoline.

Although I'm sure we all know all gasoline is very flammable and it must be handled and stored with extreme care. However, under certain exceptional circumstances, RFG (Reformulated Gasoline) may present a hazard which conventional gasoline does not.

Typically, the gasoline/air mixture in a vapor space -- the space above the liquid in a fuel tank or storage container -- will not burn at normal ambient conditions because too little air (oxygen) is present. When the tank/container is filled with gasoline, much of the air is displaced by gasoline vapor. Because summer RFG has a lower vapor pressure, it will form less vapor and displace less air under the same circumstances. When summer RFG is handled at very cold temperatures -- which might occur in certain areas during the spring transition period -- it will form even less vapor. At temperatures below 20°F, the gasoline/air mixture in the vapor space above a lower-vapor-pressure summer RFG could become flammable. This creates the risk of fire if a source of ignition is present.

Anyone who handles gasoline should be aware of, and consistently and carefully follow, current safety guidelines. This includes keeping sources of ignition away from gasoline and gasoline away from sources of ignition. While this precaution applies to all gasolines at all temperatures, the above explanation shows that it is especially important for RFG at low temperatures. In addition, if you store RFG purchased in the spring or summer at very cold temperatures, it may be prudent to keep the container as full as possible to minimize the vapor space.

Safety first!

 

[Tuna]

I'll jump in here now:

Ken: great post.

Anyone that is working on gas tanks needs to be very careful and well trained. My dad owned a small garage when I was young and I considered him to be the best but he had a gas tank blow up on him one time and put several stitches in his left hand - lucky it wasn't worse.

Okay, that's said, be careful messing with fuel tanks. Now for my personal story:

I had a problem with rust in my 96 fuel tank a few years ago. The fuel sender unit was rusted!!! My mechanic removed the fuel tank unit and used a long handle magnet to get a quarter cup of rust particles out of the tank. Since the gas level was below 2 gallons, he then used a mop like thing with a short handle and small head to swab out the tank while still in the car. He replaced the fuel filter but with the output disconnected, added some gas and ran the fuel pump to empty the tank. He then replaced the fuel filter again and put it all back together. I never had another problem with the car but I did change the fuel filter again after a few thousand miles just to make sure it didn't did plugged up with any left over rust and stuff.

Now back to the real question - unless there is a really good reason to drain the tank and clean it, it's probably better to leave it alone or leave it or professionals.

 

[Ken]

... had a gas tank blow up

Fuel vapor is much more dangerous than liquid fuel, the liquid doesn't burn - the vapors do; and when the vapors combine with an ignition source within a closed space, such as a gasoline tank that wasn't properly purged, you've got a bomb on your hands. He's lucky that he's alive! :eek

_ken

 

[Mac]

Aside from the precautions necessary when dealing with gasoline, it's not prudent to use the fuel pump to empty the tank. The fuel pump depends on the gasoline for cooling. Running the tank dry using the fuel pump means the pump could overheat and be damaged.

 

[drags1998]

PLEASE, IF YOU DO DECIDE TO DO THIS YOURSELF,BE CAREFUL!!! I have seen first hand what can happen.( we had a friend that was Burned beyond recognition,and died 4 years later)Im not saying dont do it, JUST BE CAREFUL!!!!!! :cry

 

[Tuna]

Fuel vapor is much more dangerous than liquid fuel, the liquid doesn't burn - the vapors do; and when the vapors combine with an ignition source within a closed space, such as a gasoline tank that wasn't properly purged, you've got a bomb on your hands. He's lucky that he's alive! :eek

_ken

In my dad's case, the tank had a hole punched in it - again. My dad drained the tank, flushed it with water and then filled it with water again so he could weld the hole - so far, so good. The problem was the first repair was a small plate welded to the tank that allowed fuel between the tank and the plate. That little bit of fuel trapped in between the tank did not wash out and the plate blew off when the torch was applied. Part of that plate hit my dad's hand. Needless to say, the tank was unrepairable after that!

If that plate had hit my dad in the head, it would have been a different story.

 

[Bob Chadwick]

I'm with these guys. An empty gas tank is far more dangerous than a full one because te vapors are what ignite. As already pointed out the tank should be filled with water and drained before trying to remove it. One of the Vette magazines just did an article on C3 tank removal and was very clear on this issue and the others raised here. SAFETY first.

 

[jenavet]

not worth the effort

jeepie
i just shipped 2 fuel tanks out of wrecks i have...the first one was out of a 90 and i shipped that to maine.....the second one is out of a 91 and that went to hawaii......both tanks were half full with fuel and my brother helped me drain them both...we had a large fuel jug and then used one of those super wide funnels with a micro screen in the drain for preventing particals from getting into the fuel jug.....and to be honest with you jeepie,the amount of debris and crap that came out of those tanks was so minor,i dont think it would be worth the effort to wash/clean out the tank in your car...i think between changing the sock at the bottom of your pump and your fuel filter,you should have more than sufficient filtering......after we drained the tanks,i filled them with water and a soapy cleaner and between my long skinny arm and a toilet bowl brush,i cleaned the insides of the tanks very thoroughly...but the insides looked the same when i was done...i mainly did this to dilute/remove any remaining gas and eliminate the odor so i could ship them.......so all this work isnt necessary as far as maintenance of your fuel system.