Safely installing a return line

[Matt Cramer]

It looks like the only simple option I have for mounting a return line is to drill a hole in the gas tank and use some sort of bulkhead fitting with a gasket to seal the fuel in. Right now the tank is on the car and contains some gasoline (It's been in there for two years, so it might actually just contain varnish...). I'm a bit worried about drilling into a tank that might have fumes in it. Here are the options I can think of.

1. Drill into the tank with the tank still on the car and full of gas.

2. Remove the tank, drain it, and drill it without taking any further precautions.

3. Remove the tank, drain it, and fill it with water before drilling into it.

How much caution do I need?

[Minami Kotaro]

Drilling is less likely to set it off then welding but you can't be too careful with gas. I would drain it, remove it, and fill it with water.

Is there any way your return line could go to the top of the tank, like I've seen on some fuel cells? Less worry about leakage.

[woh]

Sometimes the fuel filler to the tank is a separate steel pipe or rubber. If that is the case, you can remove that to fit a return line. This way the return line will come to the filler and not directly to the tank. This will work just fine.

If you do have to drill the tank, remove it and rinse it with water before attempting to drill it. You can not be too carefull when it comes to gasoline fumes. It's the gasoline fumes mixed with air that is the problem. Sparks internal to the drill will easily ignite the mixture.

[PSIG]

I used the filler neck for the return location last time and it was slick as I used a press-in fitting and sealing grommet used in aircraft fuel tanks like this:

Most fuel tanks have a plate where the lines and connections for the fuel level sender go. This is a popular place to add the hole or tube without dealing with the tank directly.

Finally if you really must punch through the tank then take it to a truck repair facility like the big semi trucks use. They weld on fuel tanks all the time and flood them with inert gas while welding. A common job for them. Call ahead to get instructions.

Hope that helps,
David

[Matt Cramer]

Thanks, everyone. After looking at the factory service manual, it appears I don't really need to drop the tank to do this. While most of the filler tube is in the trunk (I really didn't like the thought of using a bulkhead connector and running the return line into there), there is a portion of the tube that runs under the trunk floor where I can attach a fitting. On the other hand, it seems that it would be quieter if I had the fuel return towards the bottom of the tank, so maybe I will drop the tank and rinse it out. Probably could use a good scouring anyway.

[Matt Cramer]

So today I dropped the tank. May have a gas tank shop clean it out. Whatever was in there seemed kind of green and didn't smell like gas should.

[jsmcortina]

I've jet washed mine (or just hose and washing up liquid) then I tend to fill with CO2 from the mig welder before doing anything. Plus leave it outside for a day or so if you want extra piece of mind.

James

[Matt Cramer]

(or just hose and washing up liquid)

That's what I did today, plus giving it a little rinse with rubbing alchohol as I had some difficulty getting all the water out. Tomorrow I've got to pick up some AN fittings and will see if I can take care of the return line then.

[woh]

If possible, put the return line next to the feed line. Or better yet put both of them in a little 'can' with small holes in the can and the top open. The little can can be taken from an existing in tank fuel pump assembly at a salvage yard.

This will prevent starving the fuel pump on turns when the tank is low. Not essential for a road car, but it will allow you to run the tank closer to empty.

[Matt Cramer]

Thanks, Woh, but I've already got a good-sized surge tank on there. I plan to autocross the Dart, so I was already trying to build a slosh-proof setup.