need help with fuel tank mod for generator - gravi

[zog]

Hi everyone!

I purchased a 36' motorhome last year that didn't have the factory generator anymore. The dealer gave me a Powerhouse PH3100Ri generator, (http://www.powerhouse-products.com/powerhouse_product/ph3100ri/), to make up for the missing geny. What I am trying to do is mount the generator in the bay that held the original factory generator. The actual motor fits, and I have worked out the wiring, cooling and the exhaust,




My problem is the fuel system. The original generator had a fuel pump that would draw fuel from the main RV fuel tank. The Powerhouse generator has a gravity fed carburetor. Originally, I was planning to hook up a low pressure fuel pump and a fuel regulator to feed the generator engine, however, I realized that when the generator was under load, it would require more fuel and I would have to hack some kind of electric valve to allow more fuel on demand.

Now I'm thinking that it would be easier to mount the original fuel tank for the generator in the bay above the generator, but connected to the RV fuel tank with a pump. What I want to do is have some kind of gas tank float that when the fuel goes down to about 1/4 - 1/3 tank, the fuel pump will kick in and refill the generator tank, then turn off when the tank gets to about 2/3 - 3/4 full. This way I don't have to make a complicated system to remove the generator tank every time I need to refill it.

Here are the dimensions on the fuel tank:

15.5" w
16.5" d
6.5" h




Any suggestion would be appreciated!

Thanks

zog

 

[Rand]

I'd use a fuel return line and a pump system without a tank.

basically you run a high mounted fuel return line which then gives the lower carb "fuel pressure similar to gravity feed"

try googling it.

or you could just do something similar with the tank. have a fuel line to it.. and a higher fuel return line for excess fuel to travel back.

But tankless would probably be better.

 

[09_GXP]

I've seen a lot of guys use a vacuum system to keep their generators full. Each application is a little different but it might be worth looking into. Just searching for "generator extended run fuel tank system" can give some interesting ideas and paths to go down.

 

[FastLane]

I would just look for a used generator that has a fuel pump. My Briggs 11 hp does and it uses a common fuel pump that many manufactures use. Use a plastic boat fuel tank and leave it outside of the RV. I helped my friend with a similar setup. We just used a marine quick disconnect so he can disconnect the tank.

 

[Kawiguy454]

Stay away from a float tank refill idea. First time the float sticks it could flood the gen bay and catch fire not to mention venting of fumes as the secondary tank gets filled ....BOOM.

Best ideas were to get a purpose made pump that gets low pressure gas to the carb and circulates unused back to the main tank. I see lots of rubber hoses in the picture after a couple years that may be a hazard. May want to bend up a set of steel lines.

 

[Johnny2Bad]

An automotive fuel sender and a switch that senses impedance would work fine. The fuel sender will output a varying impedance (resistance, in ohms) depending on the fuel level, designed to work with the fuel gauge to indicate fuel level. The various types have different parameters (Ford style, GM style) but regardless, there will be an impedance that correlates to ¼ tank full. When you measure that impedance, have a relay close and pump the fuel into the remote tank. Similarly, there will be a different (higher or lower) impedance at the near full point. That would be your relay cut-off to stop pumping.

Sounds like about $20 worth of DIY electronics to me, plus a sender you could get at a junkyard if necessary. They don't really wear out.

If this sounds too difficult or dangerous (see previous post) to you, no problem. Just install the fuel sender and the appropriate gauge, and a switch in the cockpit that controls the pump. You can view the fuel level and operate the pump in real time. Be sure to get to know the sender/gauge combo to see how they react ... I've seen some Ford-type senders that were very slow to react to fuel input, to the point where the gauge didn't read full until two minutes after I left the filling station. The GM style units seem to work much faster.

Or an electric fuel pump with a return line to the main tank. There are lots of solutions to this problem, none are particularly expensive.

Oh, one more thing. Never deal with that dealership again. You got a generator worth maybe as little as 1/10th what the original one cost.

I also don't know what difference it makes that the carb was "gravity fed". They still have a float bowl to regulate fuel, don't they? Same as any other carb, pump fed or gravity fed. Don't over-complicate it (unless I'm missing something).

 

[meep]

I don't like it. you want the genset to be run-and-forget, assuming it's a good quiet one. any hobby-made system has risks. If you need a pump solution, the farthest I'd go would be an OPE pulse pump, which works off of pressures in the crankcase in the genset engine. they are small and lower pressure. you just need a breather tap off the crankcase, and the carb would need to be fitted with a plumbed float drain to drain any excess gas out of the RV if the float malfunctioned.

I also thing the closed-loop return-system above has merit.

But in the end, if it were me, and my wife and kids, I don't think I'd attempt this. Even if the design is good, you won't have the resources to test for and resolve various failure modes. Instead I'd either get the right kind of onboard unit, or pick of a 2kw or 3kw inverter genset and store it in the cubby.

Note- the extended runtime setups that rely on vacuum require a generator that has a small onbaord fuel pump. these use the crankcase pulse pump mentioned above. Honda EU2000 is such an example - it has a pump about the size of a half-dollar on the side of the engine. My B&S 14.5 hp rider has one mounted on the shroud, with a short hose to the engine CC.

This would work with either a main tank pull or the external marine tank mentioned earlier too. NOTE--- does the main RV tank stay sealed for emissions? if so, you might still want a regulator to prevent tank pressures from overwhelming the carb. I don't know how much pressure the typical ope carb can handle. ... (thinking out loud) ... which takes me back to just not being thrilled with a DIY auxiliary fuel delivery adaptation....

sorry - not trying to rain on your parade-- gasoline is not something to take lightly and we can become passive with it as an everyday fluid. my $0.02.