As many know welding on a fuel tank is something that can go drastically wrong. I find myself needing to add a sump to a tank on a car Im building and not sure of how to handle this task. Im working on an older dodge, 66 dart, and I plan on doing some drag racing a few times a year. For this I should have a sump, so the need to drill the tank then weld a sump onto the bottom has confronted me. Has anyone here done anything like this and what safety precautions did you follow.
I know the safest way to add a sump is to buy a fuel cell with a sump already on it, but that means losing my spare tire well and I dont want to do that as I plan on driving on the street and I want to carry a spare. I know we are vette owners here but many have other cars so Im sure others here have crossed this situation before.

As always Thanks in advance for your suggestions and comments.
Rodney

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I had a hole taken care of on one of my cars a long time ago. The guy that did it said it was not a big issue working on gas tanks.  He said getting it cleaned out and then it was almost like welding any other thin metal tank.  

The main danger is fuel vapors. Even if the tank has been empty for a while, vapors still remain, and can be deadly if ignited. Lost a friend years ago from a tank explosion. Working in a salvage yard, and he was dragging(by hand) a tank across the yard when it hit a rock or something that sparked. Tank exploded. Came out of a car that had been sitting in the yard for years, and the tank was completely dry.... 

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Joel Adams
C3VR Lifetime Member #56    
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"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"

It is the vapors that is dangerous.  

Most people do not realize that liquid oil and gas have the same flash points.  But gas vapors have a much lower flash point.  

Buy a new one at http://www.genesisautoparts.com/gas_fuel_tank-dodge-dart-1966.htm and weld away knowing there are no lingering vapors within.  That is, if $250 is in the budget.

I have welded on a few gas tanks and I use CO2 to purge the tank. I used a wire feed welder and taped into the CO2 line that shields the wire when welding. I let the CO2 flow into the tank for a few minutes before I started welding and kept it flowing while i welded on it. Hope this helps.