How to add an aux fuel tank to a generator

If you have a generator that only has enough fuel capacity for a single gallon of gas, it probably only runs for a good 2.5 - 3 hours tops. That just does not cut it for most emergency situations or when you need to leave the generator running for long periods of time. Here is how you can make an auxiliary fuel tank to feed your generator.

Difficulty: Moderate

Instructions

Things You'll Need:

• 3 1/2 gallon or 6 gallon marine gas tank
• 2 marine gas tank fittings (black pastic)
• 2 brass marine fittingsfor gas tank
• marine hose w/squeeze ball
• 2 small hose clamps
• Drill
• 1/2 diameter hole bit
• Extra cap for your generator (optional)
• silicone sealant (optional)

1. 
    

   You can get all of the materials you need at a WalMart Super-center or boating supply company. Purchase a marine gas tank (mine is a 6 gallon), 2 plastic marine fittings , 2 brass fitting, and a marine hose w/squeeze ball. You may optionally order an extra cap for your generator from the dealer or manufacturer, but I just used my original gas cap. Total cost was approx $55.

2. 
    

   Lay out all of your parts. Look a the picture for reference of the parts.

3. 
    

   Take one of the brass fittings out of its package and connect it to the marine gas tank you purchased. The importance of purchasing a marine gas tank is that it has a special vent system and a special line hook up attachement. See the next step picture.

4. 
    

   Take your black plastic marine gas connecor and fit it over the brass fitting on your tank. See picture.

5. 
    

   Here is an image of the gas can - see the large vent on your left - open this vent.

6. Take your gas cap off of your generator and place it on a solid table or on a concrete floor with a scrap piece of wood under it.

7. 
    

   Get your drill and 1/2 hole bit and drill a 1/2 diameter hole directly in the center of the gas cap. Drill straight and slowly. YOU DO NOT WANT TO MAKE THE HOLE ANY BIGGER THAN 1/2 in diameter, otherwise you will need to caulk it up.

8. 
    

   Screw the second brass marine fittings into your generator cap through the hole you just drilled. If you drilled the hole correctly, there will be enough plastic left to grab onto the threads of the brass fitting and it will tap itself into the hole. If not, then you have to use silicon caulk to seal up the hole to hold the fitting. I did not have to caulk mine, so you will not see that in the picture.

9. 
    

   Another picture of the generator cap.

10. 
     

    Now take the second black plastic marine gas fitting and put it over the brass fitting on your generator cap.

11. 
     

    Screw your generator gas cap with fitting back onto your generator.

12. Set the marine tank beside the generator at least three feet away if possible.

13. 
     

    Get your marine ballpump and hose. This is going to be the line you connect the tank and the generator with. Before connecting it up, look for the direction arrow on the pump, and install the pump with the arrow going to the generator - this is the gas flow.

14. 
     

    Install one end of the marine hose with the squeeze pump to the fitting on the gas tank. Use the small hose clamp to secure it onto the fitting in case you have to move the tank around.

15. 
     

    Make sure the hose is connected tightly to the tank.

16. 
     

    Install the other end of the marine hose to the new fitting at the top of the generator gas cap. Use the seconde hose clamp here to secure the hose. Generators vibrate like made, and you do not want the hose to come off. I took it back off of the generator for a better picture to show you.

17. 
     

    Here is what your setup should look like right now.

18. Give the squeeze ball two to three good pumps to prime the line. This works best if you already have a full tank of gas in the generator, but it is not necessary. The theory behind how this works is that the engine will suck the gas through the marine hose.

19. Run your generator, and enjoy the fact that you probably bought yourself a few more hours of run-time and less refueling trips.

Tips & Warnings

• If you get a marine tank with an extra air port, make sure it is open to allow the engine to suck the gas out, otherwise a vacuum will form, and the gas will not flow out of the tank.
• It is best to always have a full tank of gas in the generator when starting it up to avoid causing damage to your generator.
• Keep the extra tank at least three feet from your generator and on level ground.

[bmerritt]

on 1/14/2010 mar10s: It should work the same way if you tap into your gas line. I would be careful not to ruin the fitting through on the steel pipes. In your case, I would just bypass the old fuel tank and run the marine tank directly into the line. Try it and let me know if it works!

[mar10s]

on 12/1/2009 I have older 4400 watt generator with a briggs engine, the gas tank is steel with steel gas cap. Instead of running the gas line from the marine tank to the gas tank, could I just tap into the fuel line?

[rsansoucy]

on 11/12/2009 I followed your directions. Great idea. I built a cover(table) for the gen. and a smaller one for the tank. Can I piggyback the tank on top of the gen.?

[bmerritt]

on 10/8/2009 Spadetrump: Excellent point. This may be the case! i did not even think of that!

[bmerritt]

on 10/8/2009 Kearney's statement is incorrect. My generator does not have a fuel pump, it is gravity fed and it works fine.