Gas In Oil

[Southern Comfort]

I have gas in my oil on my Kohler CH730 engine

 

[Sprinklerman]

Stuck float in carb is one possibility

 

[bigdeano]

I see that engine is listed as having a mechanical fuel pump. If the diaphragm has a hole in it it will pump the crankcase full of gas unless they've provided a vent hole or something to prevent it. Had it happen on a car once.

 

[CobyRupert]

How much gas in the oil?
Am I correct in my thinking that many gas engines get some blow by, but rely on the engine coming up to temperature to evaporate the gas out of the oil?
Thus a motor that is repeatedly run for only short periods of time and never comes up to temp can end up with gas in the oil?

 

[tjkubota93]

How much gas in the oil?
Am I correct in my thinking that many gas engines get some blow by, but rely on the engine coming up to temperature to evaporate the gas out of the oil?
Thus a motor that is repeatedly run for only short periods of time and never comes up to temp can end up with gas in the oil?

Kinda. It is helpful to run an engine at operating temperature for a while instead of just start and stop alot. The blow by has a lot of other things in it including gasoline or diesel fuel (should not be much raw fuel). Running at operating temp does help to get all the blow by crud and condensation out.

 

[TractorGuy]

Look on the bottom of the float bowl to see if it has a solenoid on it. Some small engines are fitted with a fuel shutoff solenoid on the main jet to prevent it from siphoning into the cylinder when the engine is turned off. Had that fail on a B&S engine and kept filling the crankcase full of gas. New carb was as cheap as replacing the solenoid. Also had to change oil twice.

 

[banjodunn]

I see that engine is listed as having a mechanical fuel pump. If the diaphragm has a hole in it it will pump the crankcase full of gas unless they've provided a vent hole or something to prevent it. Had it happen on a car once.

X2 It is not common but it does happen, fuel pumps are mounted on the rocker cover and if leaking will leak into the oil

Jon

 

[Dave M7040]

See the shop manual at the link below.
On page 22 the two possible fuel pumps are described.
In my experience the most common one is the vacuum pulse style.
If something is wrong internally with this pump the vacuum can suck gas into the engine.
http://www.mcelroy.com/documents/tr...H670_CH680_CH730_CH740_CH750_REVISED+1_12.pdf
The pulse style pump is $40 from amazon.
Amazon.com: Fuel Pump for Briggs & Stratton 491922,808656, Honda 16700-Z0J-003,Kawasaki 49040-7001,Kohler 24 393 04S,24393 16S, John Deere Lg808656 M138498 M145667: Automotive
Dave M7040

 

[Southern Comfort]

Thanks for all the replies. Definitely helps. I figured it had to be either fuel pump or carb. Going to give the engine a bath all full of oil. If it is the fuel pump could I replace it with an electric one that would eliminate the fuel pump in the future. I worry that with an electric pump I should have constant pressure of gas at my fuel bowl on the carb. Do you think I need a return for my fuel to the gas tank? Thanks everyone for the replies

 

[Dave M7040]

southern
Electric pumps deliver far too great a pressure to be controlled by the needle and seat in the float bowl.
Have you determined if you have the vacuum pulse pump or not?
There is nothing to be gained by an electric pump.
The proper Kohler pump will give years of trouble free service.
There is no point in re engineering the factory design and a lot of risk
Your experiences are unusual.
Dave M7040