Larger Fuel Tank

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  #1  
Old 02-22-02, 12:21 PM
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Question siphon gas from marine tank to generator

I have a gas powered generator, 5 hp, with a 1 quart gas tank. I use it for power outages in my home. I want to add a larger gas tank. I bought a marine gas tank and plan to siphon gas from it into my my generator, bypassing the generators 1qt tank. Here is a small pic showing setup.


I have not yet bought the connectors and hose to connect this, and my generator is now stored away. Before I spend the time to make this new tank work, my question is, will it work? Will it siphon gas from the tank into the engine? I know I will have to mount the new tank above the engine and prime the gas line with fuel.

The marine tank fuel outlet connector is attached to a fuel rail inside the tank that runs to the bottom of the tank. I illustrate this on the above link.

If the distance from the bottom of the tank, to the top of siphon hose, is 8 or more inches, will that distance maintain a siphon effect? Do you have any suggestions in general before I buy parts and assemble this home made siphon setup.

Lugnut
 

Last edited by Lugnut; 02-22-02 at 12:37 PM.
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  #2  
Old 02-22-02, 01:47 PM
Fisher
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It is highly doubtful you could make this work, and the danger of
trying is high. If you could post the engine's model numbers, we
could have a prayer of being more specific. But in general, if you
maintain a siphon, how will it shut itself off? If it was a bowl
type carb and you bypassed the original tank and kept the
fuel tank above the carb, it might work, but I would not feel real
comfortable rigging up a fuel system to a generator serving
unattended in a power outage setting. The generator you have
with such a small fuel capacity, means it is too small for anything
too serious service wise, so I would advise against any attempts
at rigging like you have described.
fish
 
  #3  
Old 02-22-02, 06:07 PM
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I agree with Fisher, safety is an issue. Also, as Fisher implied, if it only has a 1 qt tank, it is not intended for extended-run usage. It will likely be in need of oil before the large tank runs dry. If you run 1 qt at a time, it gives you intervals to check oil, temp, etc...

Most small engines are not designed to be left to run for hours unattended.
 
  #4  
Old 02-22-02, 07:55 PM
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Thumbs up Safety first.

Hi all,

Fisher, you cited
" if you maintain a siphon, how will it shut itself off?"
The gas flow will be controlled identically to the manufacturers gas flow, whatever that method is. Probably a needle valve in the carb. It's a Coleman with Briggs and Stratton engine, you I would speculate a carb, bowl and needle valve, but I really don't know. The carb is hidden with plastic shielding that I don't want to remove.

You also cited,
"I would not feel real comfortable rigging up a fuel system to a generator serving unattended in a power outage setting. "

I'm not certain what your concerns are.

Cheese, you cited safety as an issue also. Not sure what you mean.

Do you both mean leaking gas lines from a poorly mounted aux tank? If so, fear not, I would weld up a fixed bracket to affix the aux tank to avoid the certain danger of tank movement. Without a fixed setup, I would agree that a free standing tank is not safe at all and not worth the risk.

I agree that long running unattended service carrys with it an added risk. I turn it off when I leave the homestead. On the other hand, I was stuck at home for all 5 days of outage, and had to fill the generator every hour. That's fun for the first 2 hours, but quickly get frustrating for the last 125 hours of outage, especially when your online to the internet when the gas runs dry, again. I respect your advice on this point, as should everyone. Adding the larger tank does irreversibly introduce the human error factor. After all, no one can guarentee their generator will run always run "attended". (Not even me ) Nor can everyone promise the modification will be properly designed and installed; another important safety point with respect to gasoline and fire.

After the last 5 day power outage, I learned that this engine can run 10 hours before you need to top off the oil, which is how often I added oil. Actually, I was quite surprised to learn this. But then I realized that is the equivalent of a few months of lawn mowing, but never experienced it before.

I do know that some equipment is not designed for long running conditions. The best example I have is my $99 110v air compressor and tank. I think 15 minutes is the max you can run it. However, my Coleman owners manual does not warn against long running conditions, aside from checking oil. Either way, big gas tank or small, it will be running the same number of hours. The only difference between the two is that I must set a kitchen timer for 60 minutes each time I fuel up.

As an added important point, these long outages only occur in the winter, so overheating the generator has been taken into account for this tank modification. If it were in the hot summer, I would recertify the modification by taking hourly temp readings with my infrared thermometer, before I would feel safe around running it for 10 hours straight. I might even put the generator in a fire resistent location, (concrete pad, metal wall, etc) for summer usage.

As near as I can tell, the only difference between two 'like' generators, (big tank & small tank) is that the larger tank requires a much larger steel frame to hold it. Thus priced accordingly. Generally about $100 more. I would gladly sell mine, but I refuse to run ads and answer the phone for 2 weeks after its sold.

Fisher, you cited,
"If it was a bowl type carb and you bypassed the original tank and kept the
fuel tank above the carb, it might work...."

As you say, I think it might work also, otherwise I would have bought the aux tank. However, the way my luck goes, I will spend 2 weekends messy with it only to find out that there is some law of physics that every boat owner knows that will hinder my objective. I might guess that your trying to tell me that in theory, it will work. That is what I am looking for.

I was taking the chance that someone has done alot of siphoning (legally ) Then this small engine forum came to mind. I don't admit to working on small engines and I don't own a boat (never have) nor ever fiddled with marine style tanks (which are kinda cool), so I limited to siphoning water out of my pool.

When I bought the tank via an internet purchase, I was really hoping that it would provide a gravity feed spout from the bottom of the fuel tank. It makes me wonder how boat motors draw gas. I can't figure that one out at all. I doubt they siphon from the tank, or do they? If boats siphon, then I can siphon. But do they???

Thanks for the feedback.

Lugnut
 
  #5  
Old 02-22-02, 08:18 PM
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Boat motors have fuel pumps. The primer bulb in the line from the tank to the motor fills everything with gas, then when the engine cranks, the fuel pump takes over.

If the tank is mounted higher than the carburetor, and all lines and connections are completely air-tight and leak-free, your idea should work. Make sure your tank is insulated from it's holding brackets by rubber to keep the vibration from eating a hole in it. Also make sure the exhaust is routed in a way which does not endanger the tank or fuel line. Good luck, Be careful.
 
  #6  
Old 02-22-02, 08:40 PM
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Cool

Thanks cheese, I find that information to be very informative and helpful, especially the boat stuff !

Lugnut
 
  #7  
Old 02-23-02, 12:38 AM
Fisher
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It is safe to assume that you have a newer
bowl type carb with a tank above it. If you
try to integrate the boat motor tank with
it, you would have to plug up the tank vent on
the smaller one, so it would be easier to leave
it out of the loop. You wouldn'y want a gasoline
mini-geyser scenario. That is what I was
implying in my first post.
If you have the carb mounted on top of a
metal tank, the boat motor tank would not
work at all.
If you post your engine's model numbers,
I could know what engine/carb you have.
Fish
 
  #8  
Old 02-23-02, 02:17 AM
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Hi Fisher,

The gas line seems to run under the tank to a carb somewhere below as you suspected. The generator model is 2 years old. I agree. I plan to remove the small tank from the loop.

Thanks for your help.

Lugnut
 
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