need help with fuel tank mod for generator - gravity feed to electric

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  #1  
Old 07-18-16, 09:24 AM
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need help with fuel tank mod for generator - gravity feed to electric

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, (PH3100Ri | Powerhouse Generators), 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,

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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

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Any suggestion would be appreciated!

Thanks

zog
 
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  #2  
Old 07-18-16, 09:33 AM
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very complicated and some things may be dangerous..

Do you know if that gen is bonded or not?

They should of gave you an actual generator thats made for that compartment IMO..

Why not just use the gen as a portable and plug the RV cord to it... Would be so much easier..
 
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Old 07-18-16, 05:05 PM
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Yeah, this is a chinese setup and I am scared to advise on any ways to do this because of the danger factor. Not only will you have to have the controls to keep the fuel levels in check, you will also have to have safeties in place to keep it from overflowing all over and starting a fire when a valve fails or whatever happens because it will. You also have to think about when the tank fills, air will have to escape and that air will be flammable vapor, so where will that go? If the unit is even suitable for being in a compartment like that, I would be more tempted to have it fed directly from the RV tank with a mechanical pule type pump.
 
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Old 07-18-16, 05:32 PM
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I kinda agree with the fore mentioned warnings!
However, if the gen has a float carb on it, maybe hooking up a vacuum fuel pump to the existing line from the RV supply...the float in the carb should hold that pressure to regulate the needs of the engine.
 
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Old 07-18-16, 06:17 PM
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@ lawrosa

"Do you know if that gen is bonded or not?"

I'm not sure what you mean here.

"They should of gave you an actual generator thats made for that compartment IMO.."

LOL. I agree, however a new Onan generator for a motor coach runs about $5000.00, used around $2000.00 +.

"Why not just use the gen as a portable and plug the RV cord to it... Would be so much easier.."

I need to be able to use the generator when driving in order to power the "house" A/C unit. The A/C that runs off the engine just isn't big enough to cool the coach on a hot day.

@ BFHFixit & cheese

I was thinking something like a modified fuel level sensor, however, since the whole fiery death thing doesn't sound like a good plan.....

I'll pull the carb and post up some pictures of it and better shots of the motor. I would probably need to drill the valve cover and install a vacuum port in order to run a vacuum fuel pump, but is would be a much simpler solution than what I have been thinking of.

And probably safer!

Thanks
 
  #6  
Old 07-18-16, 07:20 PM
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Almost any carburetor with a float control valve will be able to handle 3 psi inlet pressure, the same as output by a cheap electric fuel pump. No additional tanks, float switches, return lines or anything. Just pipe the electric pump output directly to the carburetor inlet (maybe use an in-line filter) and connect the pump power to the generator engine's ignition switch to start and stop the pump with the engine. OR, to add a bit more safety use an oil pressure activated switch to control the fuel pump.
 
  #7  
Old 07-19-16, 06:53 AM
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OK, it looks like my carburetor is the float type:

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There is also a tube running from the valve cover to the air cleaner:

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I might be able to tap into that to get my vacuum source for a vacuum driven fuel pump.

@Furd

"Almost any carburetor with a float control valve will be able to handle 3 psi inlet pressure, the same as output by a cheap electric fuel pump."

BTW, as far as a vacuum fuel pump, as there anything anyone can recommend? I'm good with large engines, not much experience with small ones.

Do you know where I can find such a pump? I've been looking, but the lowest pressure I can find is 5 - 8 psi. Also, would a 3 psi be able to compensate the fuel flow when the engine is under load?

##EDIT##

Would something like this do the job as far a a vacuum pump?

http://www.ebay.com/itm/New-Vacuum-F...wAAOSwBLlVIKAt

http://www.ebay.com/itm/Fuel-Pump-Fo...RXZ3x1&vxp=mtr
 
  #8  
Old 07-19-16, 07:14 AM
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The first link is typical on riding mowers.
 
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