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DotheDoo

Need advice-Carburetor leaking into my crankcase

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DotheDoo

Hi folks, I need some help. I have a 94' 312-8, model M 12S, Spec # 471527. It started to load up badly while running so I had my local Toro dealer look at it. Turns out the carb was leaking fuel into my crank case. He rebuilt the carb with a new carb kit, changed the oil twice to try to flush out any gas. It sat for a week in his garage and the oil level did not change. Brought it home and it ran great. Two days later is was running good but started to load up again. I checked the oil and it smells like gas and super thin. Kohler no longer makes the carburetor, part# 47 853 20-S so I searched the internet for possibly a replacement but no luck. The last option is to install a fuel cut off just before the fuel filter so after running the motor, I need to turn off the fuel line.   Has anyone found a replacement carb for this motor that may use a different part# or is there really no repair for this except a fuel line shut off?

 

Thank you

 

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WHX24

Chinese carb off fleabay should work. Funny a carb kit did not help unless it was not done proper or the dealer missed something??? 

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Stepney

Worst case you can always install a shut off valve.. however, on your era, the tank is in the back, under the seat, right? So how would it gravity feed to begin with.. if anything, that era had problems with getting fuel UP to the carb when they sat.

Sounds like shoddy troubleshooting if you ask me. 

It has a fuel pump, right? I'd bet anything there is a hole in the diaphragm. 

Edited by Stepney
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lynnmor
6 minutes ago, Stepney said:

It has a fuel pump, right? I'd bet anything there is a hole in the diaphragm. 

You beat me to it, that needs checked.

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WHX24

Good call Stepney and I must be getting old. Just had a Zturn come in with similar problem. Ditched the pulse pump and went electric. 

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ZXT
1 hour ago, Stepney said:

Worst case you can always install a shut off valve.. however, on your era, the tank is in the back, under the seat, right? So how would it gravity feed to begin with.. if anything, that era had problems with getting fuel UP to the carb when they sat.

Sounds like shoddy troubleshooting if you ask me. 

It has a fuel pump, right? I'd bet anything there is a hole in the diaphragm. 

:text-yeahthat:

 

Any time the float is adjusted correctly, and the needle and seat are known to be sealing well, look elsewhere. I'd also bet the diaphragm has a hole in it. Cheap and easy to replace once every 25 years.

 

That said, I'm not quite sure how that would cause the carburetor to "load up"... If anything a hole in the diaphragm would cause the engine to be lean. 

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WHX24

I would guess if the oil gets diluted or thinned enough by gas it would get by rings causing the engine to load up? Am I right or wrong? 

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tom2p
14 minutes ago, WHX24 said:

I would guess if the oil gets diluted or thinned enough by gas it would get by rings causing the engine to load up? Am I right or wrong? 


I don't believe so - but I could be wrong 

 

appears too much fuel dumped into engine (by carb) for whatever reason  ... too much fuel in the air/fuel mixture 



bad or stuck float ?

 

bad or stuck needle / seat ?

 

( dirt/sediment or other foreign material in the gas ? )

 

choke (butterfly) closing ?

 

Edited by tom2p

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Stepney
11 minutes ago, WHX24 said:

I would guess if the oil gets diluted or thinned enough by gas it would get by rings causing the engine to load up? Am I right or wrong? 

Doubtfully. And if that did happen, it would score the cylinder very badly. Also likely smoke like a train. 

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ZXT
34 minutes ago, WHX24 said:

I would guess if the oil gets diluted or thinned enough by gas it would get by rings causing the engine to load up? Am I right or wrong? 

It would likely just wipe out the bearings if ran long enough.

 

The oil ring scrapes the cylinder wall to prevent oil burning, so that would prevent an oil/gas mixture from working its way into the cylinder.. It would have to have a bunch of gas in the oil in order to raise the level enough to really cause an issue as far as running. Even then it would just smoke a lot. 

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bcgold
2 hours ago, WHX24 said:

Good call Stepney and I must be getting old. Just had a Zturn come in with similar problem. Ditched the pulse pump and went electric. 

 

Yea that, pulse pumps  are also known to freeze up with an ice ball from crankcase moisture leaving you stranded in the cold so you drag it into the shop trying to figure out the problem then all of a sudden the engine will start and run fine.

 

Then out in the yard again blowing or pushing snow the &^&&# quits again, you drag it back to the shop twenty minutes later the engine starts and runs fine - that is until that ice ball forms again on the vacuum side of the pulse pump.

 

Onan engines with the top mounted mechanical fuel pump have been known to fill a crankcase with raw gasoline.

Edited by bcgold

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Darb1964

Did you mention if the oil level was reading over full? If you put a off valve on you will need to close it and let the motor starve out. Then restart would take a lot of cranking, not good for motor to crank a lot on every start. Maybe a crack where carb mounts and getting in while running?? Expands as motor warms up.

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wfrpalm

Does that model have a metal tank? Maybe there is rust or dirt in the tank and it ran good until the dirt got back in the carb.

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Achto

A ton of good advice given above here.:handgestures-thumbupright: Here is one more thing to check. There is a vent hole in the body of the carburetor that goes from inside of the bowl area to the throat of the carburetor. If this hole is plugged the air inside the bowl has no place to go when gas is pumped in. This will force gas through the main jet and flood the engine.

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pullstart

I am on board with most the suggestions here... mainly float level, needle and seat being completely sealed and fuel pump possibly leaking.  The 22 hp Predator I have on my wood splitter ran less than a year with it’s stock fuel pump.  I heard about @WildmanC120‘s fuel pump issues and then read about many more on the net.  While running, my engine did the same type of symptoms loading up and bogging down.  The crankcase was so full, there was no place for the crank to move around because it was completely fluid filled.  After an oil change, the same thing happened after a couple day!s run time.  I figured carb issues, until the fuel pump diaphragm issue came up.  

 

IF YOU FIND THAT IT’S A FUEL PUMP ISSUE...

 

Either replace the pump internals with quality Kohler replacement parts (ask @prondzy how the cheap Amazon ones worked for him) or bypass it completely and install an electric fuel pump along with a fuel pump block off plate.

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wallfish

My guess is the fuel pump. Gas will typically spill out the front of the carb on a horizontal shaft Kohler if the float is leaking and not go into the case. Guess it could if the front is uphill and it leaks down through the valves.

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953 nut
12 hours ago, DotheDoo said:

I have a 94' 312-8, model M 12S,

Not sure how gravity works where your Toro Dealer's shop is, but her in North Carolina gasoline doesn't flow uphill without assistance!

The carburetor on your 312-8 is located well below the top of the cylinder block. If the float was sticking or the needle was not seating properly there would be gasoline running over the top of the carburetor. The mechanical fuel pump on your M-12 is located low on the block and a very small hole in the diaphragm would allow a great deal of gas into the crank case. 

:soapbox:

The so-called mechanics at the dealership should have known this and repaired the pump rather than wasting your time and money on an unnecessary carb. rebuild.

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Tuneup

Found the same on a golf cart with a Yamaha. Cracked diaphragm. Good luck!

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DotheDoo

A lot of good advise. Yes, it smoke like a good cigar when running. When I checked the oil level, it was clear and smelled like gas.

- Fuel pump is brand new off of EBay (New FUEL PUMP for Kohler 47 559 11-S - K321 14 hp / K341 16 hp K-Series Engines).  Fuel pump is mechanical installed below the carburetor.

- Carb rebuild kit did included new needles, float and rings.

- My fuel tank is plastic and it has a shut off valve just below it under the rear of the tank.

As fot eh shop, they have been a Toro Wheel Horse dealer for several decades and still have a few Wheel Horses brand new in crates in his inventory.

 

Yes, I thought of installing an electric fuel pump today which means I would have to fabricate a cover plate for the current mechanical pump. I picked up an inline shut off valve to install between the fuel filter and the mechanical pump and yes, new oil as well. This motor does not have an oil filter. I was told to shut off the fuel while the motor is running to run the gas down inside the carb bowl....but I am thinking, the gas has to be coming into the oil thru the new pump since it is mechanical....Hmmm.

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pfrederi

You do not have to make a block off plate.  Just bypass the mechanical fuel pump and leave it.

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WildmanC120
7 hours ago, pullstart said:

I am on board with most the suggestions here... mainly float level, needle and seat being completely sealed and fuel pump possibly leaking.  The 22 hp Predator I have on my wood splitter ran less than a year with it’s stock fuel pump.  I heard about @WildmanC120‘s fuel pump issues and then read about many more on the net.  While running, my engine did the same type of symptoms loading up and bogging down.  The crankcase was so full, there was no place for the crank to move around because it was completely fluid filled.  After an oil change, the same thing happened after a couple day!s run time.  I figured carb issues, until the fuel pump diaphragm issue came up.  

 

IF YOU FIND THAT IT’S A FUEL PUMP ISSUE...

 

Either replace the pump internals with quality Kohler replacement parts (ask @prondzy how the cheap Amazon ones worked for him) or bypass it completely and install an electric fuel pump along with a fuel pump block off plate.

 

Great advice here.  My predator only had a few hours on it before the vacuum fuel pump stopped working.  I ended up going the route of replacing it with an electric unit and have not looked back.  I used the engine all winter to snowblow and all this summer to mow 3 acres attached to a 60" deck.  

As for your issue here, I have used this carb from ebay on a K301 with great success.  I would buy one of these.

carb.PNG

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WHX24
1 hour ago, WildmanC120 said:

used this carb from ebay on a K301 with great success.

Nice that they include gaskets. Was the choke configuration right?

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tom2p

question

 

why do so many appear to be eager to replace the standard vacuum fuel pump with an electric fuel pump ?

 

the vacuum fuel pumps appear to perform well and have proven to be very reliable - often 20 or so years before any issues surface

 

obviously - electric pumps are much better for auto for a number of reasons

 

but for a 20 year old garden tractor ? 

 

Edited by tom2p
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WildmanC120
4 hours ago, WHX24 said:

Nice that they include gaskets. Was the choke configuration right?

Yes the choke was correct. 

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ZXT
38 minutes ago, tom2p said:

question

 

why do so many appear to be eager to replace the standard vacuum fuel pump with an electric fuel pump ?

 

the vacuum fuel pumps appear to perform well and have proven to be very reliable - often 20 or so years before any issues surface

 

obviously - electric pumps are much better for auto for a number of reasons

 

but for a 20 year old garden tractor ? 

 

This is something that I wonder as well. Most cheapo electric fuel pumps that people buy have the potential to put out more PSI than the float can handle.. Apparently nobody has had issues with this or they've elected not to tell anyone about it. Even on a car, most people recommend that you run a regulator with a low pressure electric fuel pump. 

 

The vacuum fuel pumps are cheap, die once a decade and are extremely simple and reliable. They've been being used for 40+ years now.. I feel that if they were inadequate, manufacturers would've switched to electric fuel pumps by now. 

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