Caution to the Kohler Commands folks...

KentT · Mar 7, 2016

The fuel pump on my CH-25 has now failed twice in about 1300 hours on the meter. Each time, the damaged pump diaphragm has allowed gravity feed from the fuel tank to fill the crankcase with gasoline. After paying $100 plus for the first OEM Kohler replacement (because you must replace both the valve cover and the fuel pump as one piece), this time I bought a low-volume, low-pressure electric fuel pump and mounted it underneath the fuel tank. No more crankcases full of fuel...

ALWAYS check the oil before starting your engine - you may find the level is rising rather than going down due to gas leaking through the pump into the valve cover, and the crankcase.

davesl708 · Mar 7, 2016

Bummer. I would think PT would have a recall on the pump if it is failing that often. I would not think it is just your bad luck to get to bad pumps in a row.

marrt · Mar 7, 2016

Good advice for any engine. This issue cost me a Subaru engine.

Marks481 · Mar 7, 2016

KentT said:
ALWAYS check the oil before starting your engine - you may find the level is rising rather than going down due to gas leaking through the pump into the valve cover, and the crankcase.

A sticking needle-valve in the carburetor can also cause this. Which is why Kohler, Briggs, and Robin all specify placing a shut-off valve in the fuel supply line (something PT doesn't do). $5 can save you a lot of grief.

Of course, you got to remember to actually shut it off when you are done using the same.... something I seldom do. I haven't installed a solenoid or motor operated valve, since that would be just one more thing to go wrong and prevent the engine from working. So maybe put a manual bypass around the electric valve...

J_J · Mar 8, 2016

I don't think the fuel pump will cause this.

It is probably the fuel needle valve . Little pin with rubber seat

Check your float valve or grit in the shut off tube and defected pin.

I have used Kohler's for a long time, and fuel shut off is GOOD investment to insure the fuel is actually stopped.

marrt · Mar 8, 2016

Totally agree on the fuel shut off valve. I had one "waiting for install" when the Subaru decided to drink it's fuel. Don't know the root cause...didn't care really as I don't like that engine. Any small gas engine with a carb and gravity fuel feed potential (almost all) should have a fuel shut off valve in my view.

KentT · Mar 8, 2016

The fuel pump diaphragm failing will absolutely cause this -- the fuel pump is made into the valve cover and mechanically driven by movement of the rocker arm, and when the diaphragm fails, gas will seep into the crankcase. A sticky needle valve (or debris under it) on the carb float will also cause a similar symptom. I've now had it happen twice, and I routinely add Seafoam (I'm a believer) to keep the carb clean. I think ethanol fuel is the culprit.

If you don't believe me about the fuel pump, read for yourself:

https://www.google.com/search?sourc...0i22i30l5.0.0.0.14074...........0.BeCY8GUw79s

Yes, a shut off valve is a good idea -- if you can remember to shut it on and off.... Meanwhile, these Kohler OEM fuel pumps are ridiculously expensive, with a short service life (if you use ethanol blend)...

Marks481 · Mar 8, 2016

KentT said:
The fuel pump diaphragm failing will absolutely cause this -- the fuel pump is made into the valve cover and mechanically driven by movement of the rocker arm, and when the diaphragm fails, gas will seep into the crankcase.

Robin will also flood the crankcase with gas if the diaphragm fails... although it is a slightly different mechanism than Kohler. The Robin pump is not directly mechanically actuated, but has a vacuum tube going to the crankcase, and pulsations in crank case pressure caused by the pistons moving up and down force the diaphragm to move and pump fuel.