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AHS

Kohler K and M fuel pumps

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AHS

Kohler M12 fuel pump; ive rebuilt….doing something wrong. Can’t seem to get it to pump. I have the diaphragm slightly off the pump and “locked in”.  Im doing everything right?  I know it will run! Show me pictures. Teach me! Thank you!!:D

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ri702bill

Silly question - are the check valves installed in their proper direction - from the tank to let fuel in, to carb to let fuel out??

Are they functional, not stuck open??

 

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AHS
8 hours ago, ri702bill said:

Silly question - are the check valves installed in their proper direction - from the tank to let fuel in, to carb to let fuel out??

Are they functional, not stuck open??

 

I never took them out. It was running once, two weeks ago. Maybe i should pop them out. How do you get the valves out? Just use compressed air?

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Gasaholic
2 hours ago, AHS said:

I never took them out. It was running once, two weeks ago. Maybe i should pop them out. How do you get the valves out? Just use compressed air?

Not unless you have replacements.  I'd suggest simply flushing them before putting it back together. (Flush check valves with some spray carb cleaner and *lightly* blow dry with compressed air)  they should NOT pop out easily and those are very hard to remove without damaging them.  When testing be sure to test with fuel supply from both directions - if you hooked fuel supply to one nipple and it doesn't pump, you could have it hooked to the outlet, in which case of course it won't. what I do after assembly of any of those pumps is hook a short piece of fuel hose to the inlet side (if you look close, some have "in" or an arrow pointing inwards to the pump stamped or molded to the body over the threaded fitting hole) and then work the mechanical lever by hand a few dozen times 

 

Those check valves, generally the pump body where they go is cast in such a way that valves will only go in one way really. plastic body pumps were notorious for the valves coming loose and falling out, so we'd stake them in (aluminum body could do that too, but not as often) but if they did fall out, often the little ring gaskets that sat under them were damaged, so we'd have to put in a pump kit with new valves anyway. 

 

But if they don't fall out by tapping body open side on a flat surface, I wouldn't remove them, as I said, they can be hard to remove without damaging them.  What could often happen sometimes is some stray debris (blade of grass, bit of animal hair, etc.) hanging up on one of the valve plates holding it open, so a close look all around the valve disk with an otoscope might show the culprit you can remove with tweezers. 

 

However if you had it running 2 weeks ago, chances are you simply put it together 180 degrees the wrong way so your inlet side is now on the outlet hose, in which case you'll find it won't pump when installed on engine.. which is why I'd always do a bench test as I mentioned above before installing just to be 100% sure it was put together correctly. 

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wallfish

You can hook up a clean piece of hose to the fuel ports and blow into it in order to quickly and easily confirm IN and OUT and or operation of the valves. The inlet side will allow easy air flow. The outlet side will not allow it or geatly reduce the amount which can pass. 

If you can blow air through both sides then the check valves are not "checking" and they're allowing flow to go in both directions. No air into either side and it's plugged up

 

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ri702bill
3 hours ago, wallfish said:

If you can blow air through both sides then the check valves are not "checking" and they're allowing flow to go in both directions. No air into either side and it's plugged up

So, John - it's either constipated or its got the runs....:D

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Bill D

I make mounting plates and use pulse pumps.  If you go this route,  use high quality OEM pumps.

IMG_20250520_212223.jpg

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wallfish
51 minutes ago, Bill D said:

use high quality OEM pumps.

Is that a Honda pump?

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Bill D
1 hour ago, wallfish said:

Is that a Honda pump?

Kawasaki 49040-0803.  All OEM fuel pumps for Kawasaki, Briggs and Kohler are made by Mikuni in Japan. 

Edited by Bill D

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AHS

Ok, ive read all the comments. The pump is on correct, the ‘IN’ side is coming from the tank and the “arrow’ is connected to the carb. It is all new 1/4” line with a filter. This has happened before when it was running; there was an old fuel line with no filter…. What if that has plugged up the inlet port on the fuel pump??

 

i will take the fuel pump off again, dismantle it and spray carb clean thru those ports. Then; run a clear line from ‘IN’ to the ‘arrow’ and pump it. Ok, thank you!!  I wont get back here till Friday, hopefully all goes. Well!!

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Bill D

Pulse pump mounting plate without the pump. 

KIMG1106.JPG

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AHS

@Bill D did you thread the top and bottom holes for the fuel pump? You must have.  I understand how you did it. I spent many times pulling the rope on a snowmobile, but it was never cause of the fuel pump!!:lol:

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Bill D
7 hours ago, AHS said:

@Bill D did you thread the top and bottom holes for the fuel pump? You must have.  I understand how you did it. I spent many times pulling the rope on a snowmobile, but it was never cause of the fuel pump!!:lol:

Here's some better photos of the pump plate.  If you have a drill press these are pretty easy to make.  I use red loctite on the screws holding the coupling nuts to the plate. I've seen multiple ways of converting old Kohlers to pulse pumps, but most require mounting the pump remotely. The pumps run about $40 at a dealer for OEM Kawasaki pumps which are made in Japan.   If you go this route, stay away from the Chinese pumps.

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