500 series push mower, gas in the oil

[slomo]

Yes, I know that. But it still doesn't answer the question.

Need your engine number to determine what you are working with. Briggs 500 tells me nothing specific. Briggs could of used several carbs and such.

Have you determined you have fuel in the oil?

Have you pulled the oil dipstick and smelled for fuel like I suggested?

 

[olgeezershonda]

Yes, I know that. But it still doesn't answer the question.

I'm leaning towards what dougand3 touched on earlier and perhaps fuel is being pushed into the crankcase between mowings due to air expansion in the fuel tank. If the gas cap is vented perhaps the vents are blocked. Check the fuel cap and/or leave it loose a bit to see if the problem persists. Just a thought.

 

[bertsmobile1]

Flot valve does not completely shut off the fuel supply
Gravity is causing the float bowl to overfil
EPA regulations require the bowl vent to be internal
So fuel runs out the bowl vent then dribbles into the cyllnder, passes the rings and fills the sump

Probably the No 3 most common problem on the entire forum

 

[Nessuno]

Flot valve does not completely shut off the fuel supply
Gravity is causing the float bowl to overfil
EPA regulations require the bowl vent to be internal
So fuel runs out the bowl vent then dribbles into the cyllnder, passes the rings and fills the sump

Probably the No 3 most common problem on the entire forum

There is no float bowl on this model. Carb sits directly above the gas tank. I posted the details in the original post.

 

[Nessuno]

Need your engine number to determine what you are working with. Briggs 500 tells me nothing specific. Briggs could of used several carbs and such.

Have you determined you have fuel in the oil?

Have you pulled the oil dipstick and smelled for fuel like I suggested?

The mower is at my niece's place for now, so I can't get the engine tag # (I thought I had a pic of it somewhere) and can't verify the oil for now. My original post has all the needed details. But if not, maybe this will help: Carburetor 795477

 

[slomo]

She's a diaphragm beauty. Air pulses from the oil sump are pushed towards the carb to pump fuel into said carb.

How about pulses in engine intake vacuum draw the pump diaphragm inward. A spring returns the diaphragm outward. A cup covers the spring to prevent damage to the thin rubber diaphragm (#13). The in and out motion of the diaphragm working in concert with the flapper check valves causes fuel to flow through the pump.

Different carb below, same principal.

 

[slomo]

I bet fuel lines are cheap for that one.

 

[Richard Milhous]

She's a diaphragm beauty. Air pulses from the oil sump are pushed towards the carb to pump fuel into said carb.

I thought those worked by suction from the intake.

 

[Nessuno]

I thought those worked by suction from the intake.

That's what I thought too, but perhaps 'slomo' is right. It's a very good question even for the gravity fed/float/bowl type carburators. Is gas 'sucked' into the combustion chamber or is it 'pressurized' into the chamber? Never gave it any thought bvefore. Here's a better pic of the carb in question. The long tube is the gas intake. I assumed the other was used in conjunction with the primer bulb. Carb 795477

 

[slomo]

I thought those worked by suction from the intake.

You are correct. I was off my meds that day LOL. I corrected my mis info above. Good catch Richard.