Extended run time fuel tank for Honda inverter generators.

We all know of the little Honda Inverter Generators. These very fuel thrifty, quiet, and reliable generators come in 1000, 2000 and 3000 Watt capacities. They are very quiet, the typical open frame generator sounds more like a lawn mower but with the quiet Hondas you can stand over one and have a normal conversation. Honda reliability is well known, many of the home center generators use Honda engines then save on the rest of the components. The only downside is cost. The little Hondas cost 3-5 times more than the home center open frame generators but their other features more than make up for it.

There are other inverter generators by other manufactures such as Yamaha and Robin Subaru. I have no experience other generators so this article is only about the Honda eu2000i. As far as I know what I am writing about also applies to the other Honda inverter generators. There are some Asian knockoffs but I am afraid they are in the realm of "you get what you pay for."

The little Hondas are very fuel thrifty. The eco throttle speeds the engine up to match the load then when the load is reduced the engine idles back. When paralleled during a sweltering Houston Texas night, the 1.1 gallon fuel tank goes for about 6 hours before running out. The other generator goes into overload and shuts down and the RV quickly heats up. Time to get out in the middle of the night and refuel. This can be avoided with an extended run time fuel tank. A six gallon outboard boat motor fuel tank can provide an additional 18 hours of runtime.

The Honda has the fuel tank near the top of the motor but uses a fuel pump. Gas caps are vented with a valve to close the vent during transport. The extended run tank is not my idea but from several others.

Like any good project the first step is to go shopping for the following.

Parts list

1. Outboard motor fuel tank. These are available in several capacities from around three gallons up to more than twenty. At over several pounds per gallon the larger tanks can get heavy when full. I found a six gallon plastic tank for just over $15. I am looking for one of the older metal tanks at a garage sale but so far I have not found a good one.
2. Fuel tank quick disconnect fittings. You will need one for the tank and one for the line. It does not matter which type you use as long as they are both the same.
3. Squeeze bulb pump and fuel line. This usually comes as a kit.
4. Six feet of 3/8' Fuel line. The fuel line in the squeeze bulb kit is not long enough.
5. Copper 3/8 barbed hose fitting tee.
6. Copper 3/8 barbed hose fitting to 1/8 NPT ell.
7. Two Honda vented gas caps. Get the OEM units. There are compatible vented available but you have to seal the gasket in the cap. There must be an airtight seal in the cap. Not all stores have the caps so you may have to order them. Gas caps from ATVs with a closable vent may fit but I have not tried them.

Optional

1. Two or three Quick disconnect sets. The ones I used were used on a project many years ago. Similar quick disconnects are available from McMaster-Carr. A cheaper alternative can be found in boating stores. I used the two I have but would like to add a third as I will mention in the text below.

Start building

Screw the fuel tank quick disconnect into the tank. Slip the other tank quick disconnect into the pump hose taking care to observe fuel flow direction and secure with the hose clamp. Slip the other end of the pump hose onto the base of the tee and secure with a clamp. As an option use a quick disconnect between the tee and the pump bulb. Cut the length of hose in quarters and slip the sections onto the other ends of the tee and secure. Slip and secure a quick disconnect onto the ends of the hoses from the tees, taking care that you use the same orientation as regards to fuel flow to all. Slip the other half of the quick disconnects on one end of the other sections of hose.

Now comes the fun part. The fuel caps have a vent that must be removed. On the underside is a spring, cap, and a clip. Remove the clip and it all comes apart. Now take a 1/8 NPT tap and run it through the hole. It is a loose fit. Screw the barbed to 1/8 NPT ell into the hole. I use a dab of JB Weld on the threads when they are most of the way in to provide a good seal. Let that sit for a while. When the JB Weld sets slip the tubing with the quick disconnects onto the barbed ells.

Fuel cap with ell screwed in place and sealed with JB Weld.

If you will notice I did not use a barbed to NPT ell. That is because I was able to dig most of the fittings I needed from my junk bin. I use Teflon tape on all screw fittings being very careful not to let any hang off the end.

Hose showing quick disconnects, pump bulb, and fuel caps.

As shown above there is no quick disconnect between the bulb and tee. That is something I thought about after. I will add one there when I find another quick disconnect like the ones I have. Then I will be able to hook the extended run kit up to a single generator.

Combiner and extended run fuel tank hooked up and ready to go.

With the above setup I can enjoy an evening and a full nights sleep in the most sweltering of nights. The six gallon tank is under 50# full and can be easily refueled from a smaller gas can. All it took was some time and some hardware store shopping.