Kohler Courage 26hp Sv735 shut down issue when hot

[marcomjl]

Hi, Last fall I purchased A Craftsman GS6500 tractor with a Kohler Courage 26hp SV735 engine. Now I know that was a mistake but was enticed by the 54 deck lol. I am familiar with kohler commands, I had one for 10 years on a Toro dingo. Great engine other than backfiring but was controllable from full throttle shutdowns when it was running hot.

Anyways the problem: I could mow for an hour, sometimes 30, and more recently 10-15mins then it would start to putter and shut down. Restarting immediately would only work with choke but putter then die. Letting it cool down was the only way to get it to run again till it shut down again.

Not in any particular order but I have gone through, checked, and replaced all of the fuel system and ignition.

New carb
New Kohler filter
New fuel lines 100%
New vacuum fuel pump
New ignition coils to replace Dsai coils
New spark plugs
New filter
New gas cap

Have tested and verified:
Carb is adjusted correctly for idle/full throttle.
Fuel tank cleaned and fresh gas flow.
Fuel lines gravity flow full
New gas cap vents
Fuel shutoff solenoid works (even removed pin/spring and disconnected no difference in shutdowns other than backfiring which verifies it working)
Coils gapped correctly
10 hr old oil still new looking and full. No gas in oil.
Removed head covers and justed valve lash.

Now most recently when the shutdown occurs, on restart it needs choke to start which tells me it is due related. Tested with spark testers and they flow perfectly and even so ignition is 100%. Not the last thing I installed new was the fuel pump and this was before that as The old pump was working 100%. I ran over my situation with a kohler service tech and he said there was a service bulletin on the reed breather on these motors. Making me think it is malfunctioning when it would get hot and not allow enough vacuum for the fuel pump to pump fuel causing the shut down. I popped the flywheel (epoxied half the magnets that were loose) and removed the reed breather cover. There was a little carb derbies but other than that seemed fine. Nonetheless Removes and cleaned everything and reinstalled the reed breather (blue metal flap plate and the lock tab. Before resealing the cover I rotated the motor by hand and verified on the piston stroke the reed breather opening and closing. After verifying that I sealed it up and didn稚 restart it for well over 24hrs so the rtv sealant was well cured and was very neat to not let it seal the blue metal reed flap upon install.

On restart it fired then died. I was getting no fuel. Spark tested 100%. I removed fuel line into carb and nothing was coming then a few drops of orange old gas which totally made my head spin since everything is 100% new fuel wise minus the pump and fresh week old gas is in it. I checked the pump and she wasn稚 pumping much at all. Removed it and let the fuel line after the filter/before the pump gravity drain and an ounce or two of orange old gas came out before new gas came. I can only assume some of this was in the old pump somehow???? I have run 20+ gallons of fresh gas since the new carb/ new filter/new lines/cleaned tank. Little lost on that one.

Anyways, the fuel pump was still just trickling so I got a new fuel pump and she fired and ran intermittently till I engaged the deck to stress it and then it cleared up. I mowed 10 minutes and she starts putting and shuts down. Same choke needed to restart. Made it back to the garage. Checked the discharge from the new pump and it was a small stream so new pump is working but not putting out enough. I took a large syringe full of fresh gas and hooked it to the last line into the carb and manually fed the fuel and it ran full throttle, no puttering or stalling till The syringe was dry.

So something is causing the fuel pump to not work after the motor gets hot which would make me think it痴 the reed breather but it checked out???

Existing reed breather is not operating when hot? New one would fix this? I have my doubts.

I am thinking of using a 2-3 psi electric fuel pump since I know 100% it is fuel supply. But I feel like the motor is getting robbed or power from the issue?

 

[denchen]

I have never worked on these engines, but going by what you have said and the fuel pump working by the pulsing pressure off the engine. How about the pressure in the engine getting up higher than I guess the diaphragm return spring in the fuel pump. If the pressure were to increase when more gas gets by the pistons when hot. Then the pressure in the case would increase, the spring would eventually not be able to push the fuel diaphragm back against the pressure, and would stop pumping. Perhaps if the oil filler cap was loosened or removed and a hand held over the filler, to lower the pressure in the case, it might point to the right area, or is there an engine breather that is partially blocked. Hope this might help. Good luck.

 

[tomplum]

For giggles run a piece of fuel line from the pump dropped inside a 2 gallon fuel can, set it on the belly between you legs and do a test mow.

 

[marcomjl]

I have never worked on these engines, but going by what you have said and the fuel pump working by the pulsing pressure off the engine. How about the pressure in the engine getting up higher than I guess the diaphragm return spring in the fuel pump. If the pressure were to increase when more gas gets by the pistons when hot. Then the pressure in the case would increase, the spring would eventually not be able to push the fuel diaphragm back against the pressure, and would stop pumping. Perhaps if the oil filler cap was loosened or removed and a hand held over the filler, to lower the pressure in the case, it might point to the right area, or is there an engine breather that is partially blocked. Hope this might help. Good luck.

No breather. Just the reed breather which is a thin metal flap over a hole in the crankcase that opens and closes from the stroke of the piston. I will try when it acts up again to remove the oil filler and see if that changes things. I will run a compression test before and after also while I am at it to see if a high pressure is building up.

I just ordered a fuel regulator and electric fuel pump. I really believe this might be the only way since I have pour so much time into it. Manual feeding the motor with a syringe when she was hot and acting up made it run perfect so I don稚 think there is any other way.

For giggles run a piece of fuel line from the pump dropped inside a 2 gallon fuel can, set it on the belly between you legs and do a test mow.

I have done that already. When she gets hot after 10 minutes and putters/stalls the pump gets a small trickle stream where as cold and normal before the stalling she flows like crazy at full throttle.

Issue is in the vacuum/pulse supply when hot.

 

[tomplum]

I've seen a couple of these Courage twins that ended up w/ egg shaped cylinders. I dunno if they had dropped ignition in the past on once side and were washed out w/ fuel or what.You could test your theory with manometer or find that electric pump that you talked about. The little breather valve if it works, it works. Issues with these were really if they were overfilled w/ oil and they would send oil down the breather tube.

 

[tomplum]

BTW, no oil in pulse tube or fuel pump perchance?

 

[radios1]

I put an electric fuel pump on my Briggs, and it worked flawlessly!.. it should be 7PSI or less though!.. 3-4 is good!..

 

[tomplum]

I put an electric fuel pump on my Briggs, and it worked flawlessly!.. it should be 7PSI or less though!.. 3-4 is good!..

Do you have a link or part number of what you used?

 

[MossRoad]

...
I have done that already. When she gets hot after 10 minutes and putters/stalls the pump gets a small trickle stream where as cold and normal before the stalling she flows like crazy at full throttle.

Issue is in the vacuum/pulse supply when hot.

Did you skip the fuel pump altogether by putting a temp fuel supply higher than the carb and just using a hose to the carb? That would eliminate or prove the fuel pump problem pretty quick.

 

[marcomjl]

BTW, no oil in pulse tube or fuel pump perchance?

None.