Kohler fuel system

[oilwell1415 563]

I've got a K181 with a fuel pump that I'm going to put on my 552 that currently has an H55 without a fuel pump.  I don't have anything against a fuel pump, but any way you slice it a fuel pump is another item that can fail.  I have never had gravity fail, so I'm wondering if there is a way to run the Kohler without a fuel pump.  Is it just a carb swap?  Is there some compelling reason that a fuel pump is just a better way to do things?  I'm sure they use a pump for a reason, I just don't know what that reason might be.  There have been thousands of tractor/engine combinations used without a fuel pump.  If this is just a carb swap, which carb do I need?  Alternatively, I guess I could mount the fuel tank on a 10 foot pole to get the 4psi, but that just wouldn't look very good.

[ebinmaine 67,328]

1 minute ago, oilwell1415 said:

Alternatively, I guess I could mount the fuel tank on a 10 foot pole to get the 4psi, but that just wouldn't look very good

I'd like very much to see the formula you've used to get the height of the pole figured out

[oilwell1415 563]

3 minutes ago, ebinmaine said:

I'd like very much to see the formula you've used to get the height of the pole figured out

Well, it was basically a guess.  But since you asked.....  I know that 4.33 psi is equal to 10' H2O because my brain is full of that sort of useless (usually) crap.  I also know that water weighs 8.3 lbs/gallon and gas weighs 6 lbs/gallon, so a column of gas would have to be 38% taller than a column of water to generate the same pressure.  That means a column of gas at 4.33 psi would be 13.8 feet tall.  If the pressure was dropped to 4 psi instead of 4.33 psi we would have 12.7 feet.  The tank currently sits higher than the carb, so we can deduct a little from that measurement and get the length of the pole down to about 12 feet.  I think I remember seeing that fuel pressure from 2.5-4 psi was acceptable, do dropping the length to 10 feet for a nice round number seemed reasonable.

[ebinmaine 67,328]

1 minute ago, oilwell1415 said:

reasonable

Agreed

[ebinmaine 67,328]

But you may have to trim some trees...

 

 

 

 

Seriously though. Maybe I'm a little off center here but I don't know why you NEED a fuel pump if it's a gravity drop. 

[formariz 11,987]

What is wrong with the H55? Don't trash that one.

[oilwell1415 563]

1 minute ago, ebinmaine said:

Seriously though. Maybe I'm a little off center here but I don't know why you NEED a fuel pump if it's a gravity drop. 

Some carburetors have a spring loaded needle and seat that has to have a little fuel pressure to open.  I don't know if this one is like that or not, but they are out there.  Others are adapted from smaller engines and gravity won't push enough fuel for them to operate at high power levels, so they add a pump.  I may just give this one a try without it and see what happens.

[oilwell1415 563]

1 minute ago, formariz said:

What is wrong with the H55? Don't trash that one.

Nothing, just going a different direction.  I've got other plans for the Tec.

[WHNJ701 4,165]

3 minutes ago, formariz said:

What is wrong with the H55? Don't trash that one.

I am with you on that one, once that h55d on my 551 got sorted out it's great running engine 

[formariz 11,987]

You need a #22 Carter or Kohler carburetor. If it starts to get fuel starvation at higher RPMs you may need to get one with a larger venturi to increase air velocity and therefor increase fuel suction. The #22 already has a rather large venturi . I have experimented with this in the past with good results.

[formariz 11,987]

11 minutes ago, oilwell1415 said:

Some carburetors have a spring loaded needle and seat that has to have a little fuel pressure to open

That spring I believe is attached to float and it just allows float to force needle to open or close as it floats up and down . Prevents needle from getting stuck which happens many times. I don't believe it has anything to do with fuel pressure. I have used those with gravity fed systems that basically will not have much pressure when tank is about empty.

[roadapples 6,983]

I have a 1.5 to 2.5 psi electric pump on a 16hp and it's plenty...

May be totally different. Just saying....

[ebinmaine 67,328]

I'm fairly new to this Kohler engine repair in comparison to most of you. 

Been around engines of lots of various sizes all my life though.

I'm not sure how many Kohler carburetors I've rebuilt but I would say maybe 8 or 10?

Year range going from 68 or 9 up to the early eighties on the k582.

 

I'm not saying anybody's right or wrong, just that NONE of the carburetors I've taken apart yet have had any sort of a pressure causing or pressure relief spring.

 

Because of our hilly terrain I'm not sure that I could get away with running a 16 horse purely by gravity but I've had a week fuel pump on a Kohler eight which may have not been putting out anything at all and I've had Trina's original 657 Tecumseh engine going up and down some Fair steep hills for short periods of time which were gravity fed even if maybe not on purpose.

 

 

[formariz 11,987]

Even on a K91 with a fuel tank one gets fuel starvation when going uphill specially with a load. I have been witness to that and proved it by experimenting by installing pumps of various types in those engines. 
 Any of these engines in question will work without a pump relatively well under “ normal “ circumstances, such as level terrain , and relatively low or no load . Change any of those conditions and it will faulter. I even have a 520H that with a two stage blower going up a 1/4 mile steep driveway will get fuel starvation half way up with a new vacuum pump. On way down under load, no problem. Change it to an electric pump. No problem whatsoever under any circumstances.

[wallfish 16,988]

Use the same carb and just bypass the fuel pump to go gravity feed. Route the fuel line directly to the carb. Remove the pump and cover the hole with a plate and a gasket.

[WHNJ701 4,165]

[953 nut 55,120]

Lots of garde3n tractors like the Cub originals had an engine mounted tank and no fuel pump. You should be fine with gravity feed.

[8ntruck 6,993]

Come to think of it, my 8n is gravity fed.

[Greentored 3,201]

If your fuel level is above the float level, you should be fine.

Somewhat new to small engines with factory fuel pumps so someone correct me if I'm wrong, but believe if the bowl stays full that's all you need- no fuel pressure required at the needle, just flow.

[Greentored 3,201]

...or you could tap the fuel cap with a nipple, run a section of rubber hose, and just blow in it while riding around!

[wallfish 16,988]

9 minutes ago, Greentored said:

If your fuel level is above the float level, you should be fine.

Somewhat new to small engines with factory fuel pumps so someone correct me if I'm wrong, but believe if the bowl stays full that's all you need- no fuel pressure required at the needle, just flow.

Correct but you could have issues like Formariz wrote.

Instead of blowing into the hose, how about connecting it to a bellow under your arm pit you can pump with your arm? It would be quite the entertainment for the neighbors! LoL

[ebinmaine 67,328]

1 hour ago, Greentored said:

...or you could tap the fuel cap with a nipple, run a section of rubber hose, and just blow in it while riding around!

 

1 hour ago, wallfish said:

Instead of blowing into the hose, how about connecting it to a bellow under your arm pit you can pump with your arm?

 

Both great ideas gentlemen. 

 

I must admit Mr Fish's would give better comedic aesthetics because of the movement involved with the up and down motion of the arm so as to create air pressure. 

For that reason I'm going to give 51% favor although I have to admit seeing a person on a garden tractor with a big black rubber hose coming out of their mouth and going directly into the fuel tank would certainly raise an eyebrow for me....

[Greentored 3,201]

Truth be told, if you see me riding around with a tube connected to my mouth, the other end would be connected to one of those cup holder hats.

[ebinmaine 67,328]

3 minutes ago, Greentored said:

Truth be told, if you see me riding around with a tube connected to my mouth, the other end would be connected to one of those cup holder hats.

 

........ And a bellows under your arm

[oilwell1415 563]

2 hours ago, Greentored said:

If your fuel level is above the float level, you should be fine.

Somewhat new to small engines with factory fuel pumps so someone correct me if I'm wrong, but believe if the bowl stays full that's all you need- no fuel pressure required at the needle, just flow.

That is correct, but sometimes isn't that simple.  Fuel pumped under pressure would result in a float level significantly higher than gravity feed.  Nothing a float adjustment shouldn't fix.