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Engine starts OK, but dies when the blades are engaged. Checked seat safety switch, replaced carburetor and removed fuel cap- none of these made a difference. If I turn the blades off quickly and throttle to choke the engine will continue running, so it appears the engine is not getting enough fuel. If it dies after blade engagement it will only restart with full choke and then doesn't want to run unless full choke. Let it sit for 10-15 minutes and the condition improves and I can ride around the yard with blades off. Checked service manual but it does not specify if this mower should have a fuel pump or not-this mower (Husqvarana YTH21K46; 960450026) does not have a fuel pump.


I am puzzled. Camshaft maybe? Greatly appreciate suggestions. Thanks in advance.

If it stops just like you have turned the engine off then chances are it is an electrical fault

If it is electrical then 2 things come to mind based on your post
1) problem with the seat switch or the wiring to / from the switch . Very likely
2) voltage drop causing the fuel solenoid to shut down unlikely but has been know to happen .

bertsmobile1 said:

If it stops just like you have turned the engine off then chances are it is an electrical fault

If it is electrical then 2 things come to mind based on your post
1) problem with the seat switch or the wiring to / from the switch . Very likely
2) voltage drop causing the fuel solenoid to shut down unlikely but has been know to happen .

Click to expand...

Thanks for the reply/suggestions. If I spray carb cleaner in it the engine will take off again. I will go through and check connectors and wires. This morning I started engine and let it idle with blades engaged for 10 minutes then increased engine speed then it died. I am puzzled.

So you write TV murder show scripts for living do you ?
Please put all of the observations in the original post.
Don't introduce new clues just after we have worked out who the murderer is
In that case I would be looking at a voltage drop and possibly a bad clutch which is drawing too much power .
The carb solenoid needs to see around 9V to stay open .
A bit hard to test unless you replace the solenoid with a short bolt then watch it t see if it springs open when the blades are engaged .I will not suggest clipping the plunger off because that illegal and it serves as a useful back up should the kill wire on the magneto fail ( happens ) .

Blade engagement is mechanical.

Well that changes everything
Start the engine then set the brake, slip round to the side and push the governor arm with your finger
If the engine dies then you do have a fuel supply problem.
BAd filter or debris in the fuel outlet spiggot in the tank would be the chief suspects .

Removed tank, and verified that I do not have any blockage from the fuel tank through rubber line as it connects to the carburetor. Next, I checked the fuel solenoid and it has 13.7-14.0v at WOT when the engine is acting up and cutting out.
Moving governor works fine when the engine decides to run right, but when it is not running right the governor doesn't really make a difference when it is moved manually. Engine still wants to cut out and die.

At high RPMs with blades engaged it runs terrible and can barely keep it running. At low (near idle) RPMs it is much better even with blades engaged. With blades off it will run at WOT and idle seemingly for a long time-in fact I don't recall it ever cutting at at WOT with blades off unless you engage blades then the mower totally loses it's sanity.

After it dies, it does not want to restart even with choke (usually) unless you let it sit for a few seconds. Then it restarts and repeats the same weird cycle.
Kinda hard to get a fix on this problem and describe it here.

Sounds like a main jet blockage like trash in the carburetor fuel bowl. When you mower is just running without the blades engage it is just running off the idle mixture even at full throttle. Then you engage the deck it starts using the main mixture jet.

Also note some these engine where prone to fuel vapor lock once the engine was hot which is why they added a heat shield at the Walbro carburetor. I have seen fuel to be boiling at times especially if you are using winter fuel in the Spring time. It can boil as low as 140F.

Star is right. You have a fuel delivery problem. The carb is running out of fuel or vapor locking. Biggest clue is engine doesn't want to restart after dying because the carb is empty. You say no fuel pump so it is gravity fed. Do you have an inline fuel filter? If so remove it and see what happens. The wrong fuel filter on gravity fed carbs can do exactly what you are describing.

Also check the ground wire connector from the fuel solenoid where it bolts the plastic carb isolator to the block. That bolt will come loose and allow an air leak between the isolator and the block. The single courage used one bolt for the carb into the block and the other one is square headed into the back of that plastic carb spacer. If the solenoid ground bolt comes loose the whole carb is basically loose.

@StarTech Never saw any with vapor lock issues with that engine, but have had a few that melted the solenoid wires and Kohler blamed MTD for putting a muffler 4 inches from the carb without a heat shield, and MTD blamed Kohler for overcharging voltage regulator cooking the wires. Neither one would pay for a warranty claim on that engine with solenoid problems.

Thanks for all the input everyone.

I did put a new carb on and the new carb acts exactly like the old carb.

To test vapor lock, I setup a floor fan on high to blow heat from the exhaust away from the carb since there is no heat shield on this mower (checked diagram to verify). I let the bowl fill with fuel then started mower and quickly increased RPMs to max and engaged the blades. Mower ran for about 60 seconds it started to cut out and die. I verified fuel flow all the way through to the carb.

Ground at the fuel solenoid was cleaned and checked when I replaced the carb a few days back, which was the first part I threw at this mower. Carb came with new electrical pigtail.

This mower has had a rough life. Looks like it fell off a trailer at 30mph.

Found some more craziness with this mower-it was taped but have a replacement in the mail....

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No heat shield:

so I looked up SV610-3213 and the parts diagram shows a 3 hose fuel pump. Part "24 393 16-S". I might start there and be sure it and the hoses are good. If the head gasket has blow by into the crankcase on that engine, it might cause fuel pump issues too if the signal is not clean that drives the pump.

sgkent said:

so I looked up SV610-3213 and the parts diagram shows a 3 hose fuel pump. Part "24 393 16-S". I might start there and be sure it and the hoses are good. If the head gasket has blow by into the crankcase on that engine, it might cause fuel pump issues too if the signal is not clean that drives the pump.

Click to expand...

Thanks! I was wondering if it required a fuel pump or not. The service manual only states there are two-types while leaving open the possibility that no fuel pump is also a possibility. Seems I ran across another very similar engine without a fuel pump so I kinda moved-on from the lack of fuel pump.

Fun fact: 329.3 hours on the engine.

Anyone else think this engine requires a fuel pump and that I should fit it with a pump? Seems we all think it is starving of fuel for some reason. Fuel tank is behind the engine (not under seat) and 21HP. Found this but don't see a fuel pump: https://www.purplewave.com/auction/130403/item/B5414/2011-Lawn_and_Garden-Lawn_and_Garden-Nebraska

I would look to see if one is on it.

sgkent said:

I would look to see if one is on it.

Click to expand...

Definitely not one fitted on this mower that I can see on the speed control bracket or the air cleaner base according to p.21 of the Kohler service manual. Manual also states, "Some engines are equipped with one of two optional pulse fuel pumps." I am not convinced that this mower should not have one just because it is not present now. I have no clue what happened to this mower before me.

Based on the illustration on p.31 the hole the bracket attaches to is not threaded suggesting no fuel pump- at least for that mounting location.

EDIT: This guys mower does not appear to have a fuel pump (same engine and mower):

I don't know. You put up the model number. The manual shows a fuel pump. Are you the original owner? Has it ever worked right? Is it the original motor?

The Courage singles that I have worked on that had a fuel pump the pump was mounted under the blower housing. With the fuel tank under the hood and not under the seat would suggest that no fuel pump was used.

With that being said. Kohler parts diagram shows that no fuel pump was used on that model and spec.

Try removing the filter, and with an air source blow back towards the tank. Remove Tank Cap FIRST. Don't stand over the tank. Install new clear plastic covered filter in the correct direction. Clamp fuel line and remove Float Bowl. Inspect for debris and clean. With float bowl off carb, unclamp fuel line if this is a gravity fed system. Fuel should flow out of the carb. Carefully replace float bowl and gasket. You should be able to view fuel coming into the filter.

bertsmobile1 said:

So you write TV murder show scripts for living do you ?
Please put all of the observations in the original post.
Don't introduce new clues just after we have worked out who the murderer is
In that case I would be looking at a voltage drop and possibly a bad clutch which is drawing too much power .
The carb solenoid needs to see around 9V to stay open .
A bit hard to test unless you replace the solenoid with a short bolt then watch it t see if it springs open when the blades are engaged .I will not suggest clipping the plunger off because that illegal and it serves as a useful back up should the kill wire on the magneto fail ( happens ) .

Click to expand...

Indeed Holmes.

ILENGINE said:

The Courage singles that I have worked on that had a fuel pump the pump was mounted under the blower housing. With the fuel tank under the hood and not under the seat would suggest that no fuel pump was used.

With that being said. Kohler parts diagram shows that no fuel pump was used on that model and spec.

Click to expand...

Page I - look again

sgkent said:

Kohler SV610-3213 21 Hp Engine OEM Replacement Parts From eReplacementParts.com

Shop OEM replacement parts by symptoms or model diagrams for your Kohler SV610-3213 21 Hp Engine!

www.ereplacementparts.com

Page I - look again

Click to expand...

Just because the fuel pump is shown in the diagram doesn't mean it was used. Kohler uses generic diagrams and unless you can click on a highlighted item or part number it wasn't used on that engine.

Has to be something going on inside this engine. Replaced coil due to wire damage and no change. OK I'm desperate so I will try a new spark plug.

Seems the ignition switch has been opened before and the internals were put together incorrectly causing a short to the blue wire in all positions except off. Fixed this and I had significant improvement to the longevity with blades engaged, but fuel starvation is still problem. I can mow at about 40% throttle for a while, but anything more it starts to bog down, cutout and sputter. Disengage blades and I can get it to continue running. Maybe I will remove the anti-backfire valve since I have a fuel line shut-off valve.

The Push mower said:

Seems the ignition switch has been opened before and the internals were put together incorrectly causing a short to the blue wire in all positions except off. Fixed this and I had significant improvement to the longevity with blades engaged, but fuel starvation is still problem. I can mow at about 40% throttle for a while, but anything more it starts to bog down, cutout and sputter. Disengage blades and I can get it to continue running. Maybe I will remove the anti-backfire valve since I have a fuel line shut-off valve.

Click to expand...

The anti-afterfire valve aka Fuel solenoid has nothing to do with fuel going into the carb. It's soul purpose it to help prevent that loud bang after shutting off the key. It will not prevent fuel from entering the carb, and will not prevent the carb from overflowing when the key is off if the float valve has failed.. The float valve controls the amount of fuel entering and controlling the amount of fuel in the fuel bowl.

Make sure there is nothing partially blocking the fuel inlet in the carb. Sometimes garbage will get caught up in the area between the fuel line inlet and the float valve seat which will act to cause fuel flow restriction. Or something partially blocking the fuel outlet on the fuel tank.

ILENGINE said:

The anti-afterfire valve aka Fuel solenoid has nothing to do with fuel going into the carb. It's soul purpose it to help prevent that loud bang after shutting off the key. It will not prevent fuel from entering the carb, and will not prevent the carb from overflowing when the key is off if the float valve has failed.. The float valve controls the amount of fuel entering and controlling the amount of fuel in the fuel bowl.

Click to expand...

If you are running along and the anti-backfire valve loses power the mower continues running? My understanding is the valve closes as soon as engine is turned off blocking off fuel so it does not end up in the exhaust causing the "backfire" as the engine winds down those last few strokes. One problem I am thinking is something to do with an intermittent signal to the valve due to the keyswitch problem mentioned in previous post.

Put the original carb back on and filled tank to 1/2 and get an even better result- higher RPMs (not full) and almost no cutting out UNLESS I am going forward up a hill then it gets really bad and cuts out and if I can turn around fast enough and point the nose down the hill it will stop cutting out. I have verified fuel flow at least four times. All new rubber, filter and shut-off valve. Tank, elbow and grommet were both removed. Blew air thorough at 30psi-perfect flow. New fuel lines have very little sag below carb inlet.

Intermittent cutout of the fuel solenoid would create more of a engine sputtering and backfire situation as it opens and closes, not something that you would keep running with using the choke or even preventing with kicking out the PTO.

Went through a similar situation last summer with a customers mower. Finally find what was causing the issue after having the carb apart on 4 separate occasions. Finally dug a small ball of cottonwood fluff out of the fuel inlet on the carb this was after carb cleaning and 90 psi air through the fuel inlet from the float seat outward.

The solenoid plugs off the main jet
On some carbs they will continue running on the idle jet
So it does not affect fuel coming into the carb, it stops fuel going through the main jet
If for instance if the float needle is not cutting the fuel off then the bowl will over fill & fuel will enter the engine via the float vent hole
This of course looks like very rich running and can take anything up to 1/2 to come into effect depending upon how much fuel the engine is using and how bad the float needle is leaking .
That one took months to nail down but after that pressure testing float needles became SOP ( you don't fool me twice easily ) .

Now because there are governed engines, the throttle control you move does not directly control the throttle butterfly in the carb
All it actually does is set the upper limit of butterfly opening
So when sitting there the butterfly could be open say 10%
When you start to move & put a load on the engine it will open another 5%
But when you turn the blades on and put a big load on the engine, the butterfly will open as far as it is allowed to .

If you have a fuel blockage or air leak then the engine should surge and that surging can be reduced a little by closing down the choke a little
As your engine just cuts out I am tending towards thinking you have too much fuel
Running fine on low throttle settings where the fuel is being supplied mostly via the idle jet then spluttering & dieing when the throttle is fully open and the main jet supplies the bulk of the fuel is exactly what happens when the main jet is way too big ,loose or missing all together .
The latter is very common with the Nikki carbs that have the plastic plate as it gets blown out during cleaning and if you don't know it should be there, you don't miss it .
On the twin barrel carbs the main jets are held in with just the O rings so regularly fall out but in this case you see them when you pull the carb apart .

The Push mower said:

Put the original carb back on and filled tank to 1/2 and get an even better result- higher RPMs (not full) and almost no cutting out UNLESS I am going forward up a hill then it gets really bad and cuts out and if I can turn around fast enough and point the nose down the hill it will stop cutting out. I have verified fuel flow at least four times. All new rubber, filter and shut-off valve. Tank, elbow and grommet were both removed. Blew air thorough at 30psi-perfect flow. New fuel lines have very little sag below carb inlet.

Click to expand...

I believe this is a gravity system. You say you replaced the filter. What filter are you using? Paper element? You are describing a fuel flow problem with the uphill downhill difference. Try removing the filter and running it and see what happens.

Here is the final problem. The nipple from a fuel filter broke off inside the last section of fuel line connecting to the carburetor-wasn't me. I had blew air through the lines and observed fuel flow out of the line, so I thought flow was OK. Today I decided to remove and LOOK through every section of hose and found this piece, which was just enough to reduce fuel flow causing fuel starvation. WOT w/blades engaged while mowing up a hill again....