Kohler magnum 18 no gas to carb

Hey y’all. My kohler magnum 18 recently stopped pumping gas to the carb but I can still see it getting drawn through the clear fuel filter up to the pump. The fuel pump is brand new and I opened it up to make sure it wasn’t damaged and there was no visible damage to the pump diaphragm. I hope it’s not sucking gas into the crankcase. I’m getting really fed up with this mechanical fuel pump. I’m ready to plumb a pulse pump. Anything y’all can think of?

Drop the bowl on your carb and make sure your needle is not stuck. Another possibility if it has a shutoff solenoid, that could have gone out. 2 options if so, 1 get a new one, 2 cut the plunger off the broken one.

No gas coming out the fuel line at the carb if you disconnect it from the carb and crank the engine?

I already checked the carb and it is good and no solenoid. No gas comes from the fuel line when I crank it but I see it go through the filter up to the pump and then as soon as I stop cranking it drains back down the line and out of the filter. The pump is probably bad again already but I’m just done with it.

Yikes, if it is pulling up.... hope it isn't going into the crank. Also, be sure you do not have any cracks in your fuel line that it is pulling so far but not all the way due to air in the system. Also, maybe loosen your gas cap. The vent could be clogged and it is pulling up just enough gas to get to the filter but not much further then depressurizes back to the tank.

Yeah I think it is going into the crankcase. I didn’t see any visible damage to the pump diaphragm so it pisses me off a little bit but it is what it is I guess. My friend said he saw a Taryll video where he said the cheap replacement pumps don’t last at all. I think I’m going to just go pulse pump or electric pump, what would be your choice?

Gravity. No pump. What a pain. Keep us posted.

If I run gravity feed I have to relocate the battery and I really don’t want to do that. I can get a 2.5-4 psi electric fuel pump for $12 and just wire it up to the ignition or even standalone. I read about other people doing it with good results. Seems the most reliable to me which is a big factor because I often go riding by myself with no one to tug me out.

Maybe you could carry one of these in case the pump quits.

Any chance you plumbed the pump wrong

No definitely not it was running good and then stopped working

Bypass the fuel pump by using a gravity tank as a test. Easy way to confirm the fuel pump is the issue. Then move on from there. Troubleshoot one thing at a time if possible.

I already did. Runs good. I drained the oil too and it was gassy so definitely a bad pump. Makes me mad that it only lasted 2 months but I got a electric pump, wire, fuses, all that on the way so I can wire it up. Do you just wire it into a 12V source from the ignition switch and leave it run constantly? Will it flood out the carb if it’s idling for too long? I also got all the stuff to redo the front end and I got Leds on the way so I’ll make a post about the front end when I get it done.

Also I recently posted a YouTube Short so go check that out

Maybe move the pulse to the intake? There are some sites out there on that. If you have a weak needle and seat yeah it could flood. My dad did it once. Put it on a toggle until it got started then was ok to turn off. May have to play with it.

Is there any way I could wire a toggle switch so that it’s only live when the key is on? I want everything to be dead when the key is off so nothing gets accidentally turned on. I guess I would just pull a 12V source from the switch like normal but run it through a switch, right?

Do you have a multimeter? Poke around in the key switch for 12-14 volts only when the key is on. Splice and wire there and you shouldn’t have a problem

wire the pump to your lighting wire because that will be 12v and there might also be a ground wire too most older motors run lights when the key is on but newer use a constant 12v usually

MudMachine95 wrote:

Is there any way I could wire a toggle switch so that it’s only live when the key is on? I want everything to be dead when the key is off so nothing gets accidentally turned on. I guess I would just pull a 12V source from the switch like normal but run it through a switch, right?

On older tractors the L terminal isn't on unless the key is on.  If you can, find the diagram for your switch like this.  Lets you know what is open or connected.

In Run, this one is B+L  showing they are connected. L would be a good source of keyed power.



There are some newer ones that have A1 A2. Like this,



As you see, in run only B+A1 are connected, so you would want A1.  But this has a second circuit that in a different position, gives you B+A1, but you can connect a secondary circuit of A2+L.  L and B are not connected in this one.  (Typically A1 on this goes to fuel solenoid and A2 is a charging wire that connects to lights) A1 would be a good source for keyed power on this one.

Okay my key switch is exactly like that but the terminals are moved. B+L have continuity when it is in the run position. To pull 12 V from the wire, should I just splice the pump power wire into it? Then ground the pump to the chassis? Run a switch in the middle of the positive to have a shut off.

Or just pull the 12 volts off the positive terminal if you are going to use a shut off anyway. No need for two switches. If you DO have the positive shut off, then you have to remember it. If you use the ‘L... lights’ then it is automatic. If the key is on, the pump is on and if the key is off, the pump is off.

Well like I said I want everything to be dead when I turn the key off but I also want to have control over what the pump is doing when it is running. If I’m leaving it idle I can shut it off or if I’m working on it or something. I’m just gonna throw the switch in-line and then I have it if I need it.

Why not run a separate switch off the keyswitch, so you can choose to turn the pump on when the engine is running but when the key is off the pump will always be off.

Rustbucket Garage wrote:

Why not run a separate switch off the keyswitch, so you can choose to turn the pump on when the engine is running but when the key is off the pump will always be off.

That’s exactly what I’m saying I’m going to do. When the key is on I can turn the pump on or off but when it’s off the pump is always off. I was really just asking about splicing into the power wire and the ground.

Okay so I’ve practiced all my wiring skills on my lights which look sweet btw, I went to start on the fuel pump and it has a red and a blue wire coming from the L prong on the connector. The blue wire comes out of the harness and just reconnects to itself as if it’s for an accessory that’s not on this tractor. I’m guessing the red wire is where I want to pull power from but there’s not really a great way for me to see.

I would install a fuse of about 5amps in the fuel pump wire.
Also keep in mind some small engine lawn tractor head lights wire at the switch is AC voltage and only works when the ign switch is in the LIGHTS POSITION and the engine has to be running. ((just throwing some general info at you to consider)

The electric fuel pump will turn itself off when it builds up a cut-off pressure so really no need for a 2nd switch.
A pulse pump is cheaper and lots of Kohler 20-25hp come out with a pulse pump.
You can find a Briggs pulse pump or a close rather than the more expensive Kohler pulse pump.
I do run a white briggs type gas filter when I use fuel pumps, red color filter for gravity fed. (the white color Briggs is a finer filter usually)


Keep in mind if the engine gets tipped or turned on it's side and the pulse line going to a pulse pump gets oil in the line the pump will not work until you clear the pulse hose of oil.

I would try to stay in the 2 psi max pressure for a fuel pump. 4-5 is pushing the upper limit of the needle seat.