Gas Tank Woes


Based on readership, seems there is high interest for information concerning classic car fuel systems. Our recent post concerning Ethanol was very popular. When tied to another recent post concerning a leaking gas tank in a garage, we saw where the "dots were connected"...
Rusted Gas Tank Interior

Based on available information found, a gas tank in poor condition can cause as many or more fuel problems as simply having "bad gas". Why? A tank with sludge or interior tank rust can cause long-term and repeated performance problems. As was learned by the owner who's car that had a leaking gas tank in their garage, although the exterior of the tank looked fine (for a 49 year old tank), the inside was badly rusted and the leak was from the inside out.

Usually, it's fairly easy to tell when you have a leaking gas tank - look for the wet spot or stains on your garage or driveway surface. Should you not see a leak from the bottom of your tank, know that sometimes a tank will leak from the top due to moisture and debris being caught on top of the tank and rarely gets the opportunity to full dry, causing a tank to rust, rot and leak.

So, what's the solution?

Obviously, replacing the gas tank, fuel filters and perhaps the fuel "sending unit" are well-recommended maintenance activities for any classic car with original components. Then again, if you have been performing good preventative maintenance with the use of fuel stabilizers that prevent gum and other compounds from forming; biocides will prevent microbial growth and corrosion inhibitors which prevent the formation of rust and corrosion inside your gas tank, you'll have avoided most of these problems. 

As for the process of replacing the tank itself, because there are many different requirements for accessing a tank depending on the make and model of vehicle involved, we will defer making any specific recommendation as to how best remove or install a tank. Check with your mechanic or a good reference manual for the specifics pertaining to your classic car.

But before you can drop a gas tank, there are several basic steps you can take to get started.

Carefully - drain the existing fuel from your tank.  

To drain your tank, there are two relatively easy and safe methods. First, if your tank has a drain plug, removing the plug will allow the tank contents to drain out completely. If your tank does not have a drain value, a gas siphon pump is recommended.

Here's where a warning takes place -

Dangerous and dumb
Never siphon gas by mouth. Yes, it is tried and a successful method, but it is unsafe and not at all a clean process. Remember, you are sucking on the end of a tube that has it's other end at the bottom of a gas tank floating among the debris and loose sludge particles. And the timing is never perfect - removing the tube from your lips just before the gas reaches them. Ugh!

A safer, faster and easier means is to use a manual siphon pump - one specifically approved for combustible liquids, such as gasoline. Readily available at any auto parts dealer, the cost of the siphon is well worth it for convenience and safety. Don't be too thrifty - reports of an inexpensive classic "bulb" pump failing to do the job are plentiful.

Hold the flap open with a small wooden
stick to avoid snagging the siphon hose
Although a common component of newer cars, it was not until 1975 that the anti-siphon device was mandated for use on passenger vehicles. This was also timed to coincide with the new mandate of unleaded fuel for passenger cars with a smaller filler nozzle. As such, for pre-1975 vehicles working around the anti-siphon device is not an issue. Thereafter, however, you'll have to work your siphon hose thru the device making it do what it was designed to prevent you from inserting (and removing) a siphon hose.

Once you have the gas removed, and if it is reasonably new, put it in an approved fuel container for reuse once the new tank is installed. Here again, be sure you are putting the gas in an airtight, approved container.

But what if you have contaminated "aka: bad" gasoline to deal with - what do you do next?

For sure, it is far easier to advise you what we found as to what you SHOULD NOT do with it.

  • Never pour it on the ground and try burn it off.
  • Never pour it down a storm drain, sewer line, toilet or a sink drain
  • Never store gas, even temporarily, in glass containers
  • Never put the container of gas in the trash

These disposal "methods" as all dangerous, illegal and if caught, you are subject to substantial fines and penalties.

So where can you dispose of used/old/bad/contaminated gasoline?

Most municipalities have some form of hazardous fluid disposal process.  It may cost you a few dollars to dispose of your gasoline, but this is the best method.  Also, some (but not all) auto service supply dealers may take used gas as well as your used oil and filters.  Check them out locally.

Bottom line - be smart and be safe when dealing with any gasoline product.

Drive safe and enjoy your classic car daily...