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SmilinSam

Briggs 20p Intek single

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SmilinSam

Got a Briggs 20 hp Intek single cylinder here. Got it free from a guy who had it replaced by Deere under warranty as it blew a head gasket. I fixed the gasket and have had it running a number of time without issue.  It has sat alot though. Now on occasion , while sitting it will fill the combustion chamber with fuel.....and that is with the fuel shut off  in the OFF position..

This has a vacuum fuel pump.. Also, once you pull the plug and drain the fuel out, it starts right up and runs great. 

No fuel is going into the crank case....just the cylinder.

 

Whats happening here?

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PhanDad

Assuming this is a side view of the engine:

44651_2_2000x2000.jpg

Only way I'd see that happening is if the fuel solenoid is stuck open (or disabled) and

1) the shutoff valve is leaking through or

2)there's an air leak somewhere downstream of the shutoff valve (pulse pump diaphragm?).   

And as to the fuel solenoid totally stopping fuel flow, I'm not so sure of that anymore.  I thought it would but either it doesn't or it's partially open on the Command on my 75th.  In the winter I keep the fuel tank full (almost no air space) to minimize condensation risk.  I have a full shutoff in the line from the tank to the pulse pump.  Last week it was time to remove the snowblower after a month or so of sitting.  I noticed I had forgotten to turn off the shutoff valve.  Then I noticed the tank was no longer full (love those opaque tanks).  Checked the oil - over full with a smell of gas.  First time it's ever happened to me.  I've only been running a twin for about 10 years.  50 years of Briggs single cylinder use and on several occasions I've had gas running out of the carb.  I'd rather have it on the floor than in the crankcase.  

 

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SmilinSam
16 minutes ago, PhanDad said:

Assuming this is a side view of the engine:

Yep Bill, thats the engine type.

Mowed on the yard today with it for a couple hours. When I put it away today I shut the fuel shut off OFF and let the engine run till it ran out of fuel. I'll let it set a few days again and see if it fills the cylinder again. If it does, I'll pull the spark plug again and  drain the gas out.  When I get done the next time I will physically pull the fuel line off the carb, plug it,   and let it set again. See if its the valve is slowly leaking gas by.

 

I think you are right in that there are at least  a couple of things going on here....

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CarlH
14 hours ago, PhanDad said:

And as to the fuel solenoid totally stopping fuel flow, I'm not so sure of that anymore. 

On my Command horizontals I install a momentary switch (NC) and use it to kill the engine (at idle) to avoid the 'Brown Pants' syndrome.  It has worked well for me.

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PhanDad
15 minutes ago, CarlH said:

On my Command horizontals I install a momentary switch (NC) and use it to kill the engine (at idle) to avoid the 'Brown Pants' syndrome.  It has worked well for me.

A little more explanation please.

I'm thinking your momentary switch is in the +12V line to the carb fuel shutoff so you can kill the fuel flow and starve the engine for fuel before turning off the ignition switch (which kills the fuel flow and spark at the same time).  

So far I haven't experienced any backfiring when shutting down the tractor at better than 1/2 throttle using the ignition switch.  So my carb solenoid must be restricting most of the fuel flow, but maybe passing slightly to allow my recent "gas in crankcase" event.   

 

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CarlH

I do install it in the wire to the idle solenoid.  I idle the engine and engage (open) the switch until the engine starves for lack of fuel.  No BP event because there is no fuel in a cylinder to ignite from residual heat.  Different Commands seem to react differently to the 1/2 throttle shutdown and still have the BP event.  The switch always works for me.

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CarlH

PS:  The reason I am concerned with backfiring at shutdown is because Kohler Commands had problems with blowing headgaskets at first due to backfiring.  There is now a revised headgasket design that appears to take care of that.

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Horvik
On 4/9/2021 at 5:07 PM, SmilinSam said:

Got a Briggs 20 hp Intek single cylinder here. Got it free from a guy who had it replaced by Deere under warranty as it blew a head gasket. I fixed the gasket and have had it running a number of time without issue.  It has sat alot though. Now on occasion , while sitting it will fill the combustion chamber with fuel.....and that is with the fuel shut off  in the OFF position..

This has a vacuum fuel pump.. Also, once you pull the plug and drain the fuel out, it starts right up and runs great. 

No fuel is going into the crank case....just the cylinder.

 

Whats happening here?

I put manual valves in any motor I can get them into. They are foolproof (Long as I don't forget!) and don't malfunction like the B & S solenoids are known to do. 

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SmilinSam
2 minutes ago, Horvik said:

I put manual valves in any motor I can get them into. They are foolproof (Long as I don't forget!) and don't malfunction like the B & S solenoids are known to do. 

The fuel shut off I refer to above is a manual inline fuel shut off valve.

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AC716
15 minutes ago, SmilinSam said:

The fuel shut off I refer to above is a manual inline fuel shut off valve.

My thinking your shut off valve is bypassing.

 

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SmilinSam

More testing to do, but if so,  I'm thinking its getting by the manual shut off, the fuel shut off solenoid, and the float valve. 

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PGL

I'd try disconnecting the fuel line from the manual shut off and see if it leaks.  If it doesn't the solenoid and float valve won't get any gas to leak, but you may have to find the gremlin that opens it when you're not around.

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SmilinSam

Pulled the line off the out on the shut off and hung it down into a metal can for the last few days. Got about 1/4" of gas in the can for that duration. So it is indeed leaking by..

 

Heres another thing to consider.  On most tractors with these vacvcum fuel pumps, the fuel tank is below the level of the fuel pump. Pump is usually mounted on the ehgine shroud up high while the gas tank is under the drivers seat.

 This tractor has the gas tank above the engine and was originally a gravity feed into the 10hp L-head Briggs.. Bottom of the tank is about mid level with the engine and below the level of the fuel pump. The top of the tank is about 10 inches above the fuel pump..

Should the fuel pump be higher?

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PhanDad
1 hour ago, SmilinSam said:

So it is indeed leaking by..

Glad to hear you found the issue.

 

1 hour ago, SmilinSam said:

Should the fuel pump be higher?

Won't help - siphon effect - as long as the carb is lower than the tank fuel level and the line is liquid filled, the fuel will flow regardless of how high the fuel pump is.  

I just looked at the Command/fuel tank relative positions in my 75th.  I'd say the pulse fuel pump and carb are about at the same level - an inch or two above the bottom of the tank.  So I'd say the only reason there's a fuel pump is to be able to use the last inch or so of fuel.  

I've only had one Kohler single cylinder powered "Sovereign" and was surprised it had a fuel pump since to my eyes, the carb was lower than the fuel tank.  Maybe a "Kohler" standard?  (And as I think about it, I think it's the same for the KT's).

Anyway, I'm surprised there haven't been more reported issues with gas in the crankcase of a Command in a Sovereign.  The OEM setup didn't include a manual fuel shutoff valve, so all that's preventing the problem is the carb solenoid and carb float valve.   

Maybe the fuel pumps have spring loaded check valves that would also prevent flow.  I can see the mechanical fuel pumps having fairly stiff springs, but I'm not so sure about the pulse pumps.  Anyone been "inside" these pumps?  

 

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CarlH
14 minutes ago, PhanDad said:

Anyway, I'm surprised there haven't been more reported issues with gas in the crankcase of a Command in a Sovereign

I have the opposite issue with a Command powered Sovereign.  If it sits for more than couple of days, it won't start without a small shot of starting fluid.  Then it runs great under load (snowblowing up to a complete tank) and restarts instantly.  I have put on a new pulse pump, same issue.  I suppose the float valve might be letting gas evaporate, syphon, or leak out of the bowl? The carb or pump could be leaking but I see no evidence of gas in the crankcase.  I haven't taken the carb apart yet but I am going to try to replace it with a 'foreign' aftermarket carb.  That should be informative in more than one way. 666

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ShaunE
19 hours ago, CarlH said:

I have the opposite issue with a Command powered Sovereign.  If it sits for more than couple of days, it won't start without a small shot of starting fluid

Bill is correct.  I rebuilt the choke as it would not close completely.  As strange as it sounds, that 1/8" left to close would not allow it to cold start.  To test, simply remove the air cleaner & crank it with the choke closed.  Then use your finger to close it the last 1/8" & if it fires right off, that's the problem.  Also if you ever have problems with running roughly, pay close & special attention to the removable emulsion tube.  One end of mine will sometimes get debris in it & since the tube is not an open passage, it can go unnoticed unless you start using a torch tip cleaner to clear ALL the microscopic orifices & the O-Rings on each end of it.  Also, It only fits correctly in one direction.  And it IS possible to install the float upside down as well.  Ask me how I know all this...  It's because my first name is Ima & my last name is Dumb***.

Edited by ShaunE
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CarlH

Shaun,

Thanks for the insights.  I *thought* the choke was closing completely but I will check that VERY carefully the next time around.  It would explain the behavior I'm seeing.  Something about 'assuming'?

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ShaunE
4 hours ago, CarlH said:

Shaun,

Thanks for the insights.  I *thought* the choke was closing completely but I will check that VERY carefully the next time around.  It would explain the behavior I'm seeing.  Something about 'assuming'?

The biggest problem is that little tiny spring wears out.

This is the choke rebuild kit I used.  Pricey but worked like a dream. Kohler# 24 757 07-S

 

 https://www.ebay.com/itm/Genuine-Kohler-OEM-KIT-CHOKE-REPAIR-Part-24-757-07-S/291617228512?hash=item43e5bdc6e0:g:XCAAAOSwquxgOnG4

Edited by ShaunE

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SmilinSam

Bought a new plastic inline shut off just like the leaking one. Let it hang down into the can for 2-3 days and no fuel in the can. Hooked things back up and ran the tractor for a couple of hours or so mowing. Then shut the fuel off and let it run out of gas. 

Will see if there are anymore troubles next week, but it looks like it may be good now as long as I remember to shut it off after using the tractor each time.

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