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Draining fuel from historic fire engines

Hi Everyone,

I work at a museum that houses a large collection of historic fire trucks, dating from the early 20th century to the present. We’d like to preserve them for the future, and understand that draining the fuel is an important part of ensuring their longevity. Here’s the problem: Once we’ve drained or siphoned off the gas in the fuel tank, we need to let it air out to ensure that all of the gas evaporates. But that’s just not possible for us, considering all of the trucks are located inside, and we can’t have gas vapors floating all around the museum. Any suggestions on how to best handle this project?


You’re right, fuel vapors are extremely dangerous/explosive. You might call other car museums and see what they do (I have no idea). But my guess would be to drain as much as you reasonably can, and let that be it. I don’t see much harm in a few ounces of gas remaining in the tanks.

If you drain the fuel and replace the filler cap there should be no change in the rate of vapor escaping into the air nor will there be any change in the vehicle other than there is significantly less fuel to evaporate.

Here is an off the wall suggestion to get things started here: Use a garden hose with one end inserted through the tank filler into the bottom of the empty tank and a heavy duty fish tank aerator adapted to the other end of the garden hose with the aerator located outdoors. Run a short semi-rigid fuel line hose length into the filler port to make sure that fresh air has provision for intake and then duct tape the fuel tank fill port closed.

I’d occasionally check the garden hose and the aerator for possible deterioration from the fuel vapor. Run each tank for a week or two with this setup. If you have enough money to play with you could use fuel line hose for all.

You could start and run them until they are out of gas, if draining isn’t enough.

You don’t want to run gasoline fumes thru any type of electric motor/pump unless the motor being used is explosion proof.

What you can do is, insert a hose into the gas tanks that can reach outdoors. Then on the end outdoors insert a Y branch pipe fitting such as this Then on the branch part of the fitting apply compressed air. This will create a venturi effect pulling the fumes from the gas tanks.


Move the trucks outside. Remove the fuel tanks from the trucks. Use compressed air to blow out the fuel and return lines…Return the trucks to their indoor repose. After being stored outside for a month or 2, upside down and open, you can reinstall the tanks (if you wish) into the trucks…When you remove the tanks, carefully mark the tank and cap so you don’t lose track of where they go…

Depending on how many trucks you have, you may end up with a considerable quantity of old fuel. This will present a disposal problem. I would make arrangements to dispose of it BEFORE I started this project…Don’t mix the Diesel and gasoline together…

Caddyman’s suggestion is a good one. Deal with the tanks separately from the trucks, and let all the airing out happen outside.

" Caddyman’s suggestion is a good one. Deal with the tanks separately from the trucks, and let all the airing out happen outside. "

I agree, too, but I thought museums were into this stuff, routinely. What the . . .

I can only hope if they have any really old early 20th century historic fire tankers that they removed the horses from the front before putting them on permanent display !
Talk about fumes. . .


You need a positive method of moving air. If you have a little more money to spend you can buy a piston type air compressor from Harbor Freight that will more positively move air than a heavy duty fish tank aerator. The outlet of the air compressor can be connected to a length of hose to get any fuel vapors concentrated enough to ignite, away from the compressor motor. Connect your garden hose outlet or oil resistant air compressor hose outlet instead of garden hose to the intake side of the piston type air compressor. Less expensive diaphragm air compressors are available but these are quite noisy and have a shorter lifespan.

Reading between the lines of the original post, it seems evident that the OP does not want to move a large number of valuable fire engines outside; may not have a safe or large enough place for that and may be concerned with deterioration due to weathering, or worse yet, hail damage. The difficulty of removing tanks is an unknown but is a daunting task if it is like my car’s gas tank.

+1 CSA … but at least the horses would ‘drain’ themselves…

Not if they’re 110 years old they won’t :wink:

If they have gas in them, they are already outside and have been used outside, so just take care of the problem before bringing them in again-assumming they can be pushed or towed back in place again and not driven.

The easiest way to get fuel vapor out of a tank, is dry ice. When I worked at a gas station, we had our tanks replaced and the night before the guys doing the work pumped out as much as they could and then dropped in some dry ice. When the ice turns to gas it pushes out the fuel vapors because its heavyer.

As someone else suggested you can take the tanks outside overnight to do this. Otherwise you will need to figure out some way to vent the tank out side.

Bing, the guy said the vehicles are all inside.

These things are probably so massive that even moving them around is not a good option.

I suggest you don’t remove the tanks. I work on commercial vehicles and fuel tanks are heavy and unwieldy. Sometimes my colleagues use a forklift just to lower/install them.

Good points db, antiques don’t take well to frequent disassembly. But they can leak in the fuel systems. That’s why I’d think other museums would have procedures for this nailed down.

If you can’t purge the tanks, you might consider filling the tanks with Argon. That will displace the oxygen so even if there are fumes or vapors, they won’t be able to ignite.

PS, you can use your nose to check the outlet hose per my suggestion to check to determine if the task is finished for each truck.

To vent the tanks to the outside, try some flex tube like you find for dryers. Small enough to fit either the filler neck or the sending unit hole. That should be cost efficient.
Then drop in that dry ice.

My reaction to the dry ice method is that it might work well at displacing fuel vapor in each fuel tank but would, due to cooling, would reduce or nearly stop the tendency of any remaining liquid fuel to evaporate. It might work to do the process several times, giving any remaining liquid time to warm, evaporate and then become displaced out of the tank via the CO2 from the dry ice.

A question that should be addressed: Is CO2 less or more dense than gasoline vapor? CO2 needs to be more dense to remain in the tank while the fuel vapor is displaced and sent out.