B & S 15.5 carb flooding/leaking

Hello everyone. Hello Cheese!

Yesterday I smelled a strong odor of gas in my garage. I just figured it was my Toro snowthrower that I had just used (another 5" snow in E. MA). But it wasnt. It was coming from my 96 Craftsman lawn tractor - I could see a small puddle of gas under the engine. It has the B&S 15.5 engine. The original engine on this tractor expired in 2005 and I replaced with a new one 28N707 Type 1026-E1 built 11/02/99 (code 991102ZE). Basically same as the original engine.

I had not used/started this tractor since last October. I noticed gas dripping from the bottom of the carb (I typically do NOT drain gas at the end of the season). I disconnected and plugged the line from the tank and figured I start it to run off the gas in the bowl but it would not crank. So Im figuring it must be hydro-locked with gas. This was late yesterday so I did not have a chance to mess with it more. Because of the odor the tractor is now out on the driveway under a tarp. Its interesting that I never had this problem with the original engine/carb (which I still have).

I did some searching on the net and reading my B&S small engine manual late last night and confirmed that it has the Walbro LMT carb with the anti-afterfire solenoid (two wire) on the bottom of the bowl.

I guess to next step will be to remove the carb so I can open it up and check the needle/seat. Carb removal looks fairly straight forward - perhaps some fiddling with the linkages. To remove the bowl to look at the needle/seat I have to remove the solenoid, correct? Will the solenoid unscrew by hand? Once I have the bowl off is there anything else I should look at? Whats the opinion of R/R'g the seat? Im not looking to completely overhaul the carb unless I have to. I assume the minimum parts I will need are:

281165 Bowl gasket
231855 Needle
272465 Gasket
272469 Gasket (possible)
281106 O ring
494381 Float kit (possible)

Also, any advise on the best way the relieve the hydro-lock? I figure I will deal with that once the carb is off. I will pull out the spark plug and try to drain/vent from there. Should I pull the intake manifold/elbow from the crankcase? I figure the crankcase is saturated with gas too (the lower part of the air filter seemed satuarted with gas when I did a quick look). Any other advise is appreciated!!

Thanks
Paul

 

I have a toro with the walbro carb with the same problems. I bought the carb kit and replaced everything but the float seat becauce I didn't know how to, now I do. Anyway I put a line shutoff so that I can get at it and run it dry each time I use it and I have no trouble, and I may replace that float seat someday. As for the hydrolock you can take the plug out and ethier turn it over by hand, or just let it sit for an hour or two. You might want to check the oil, and mabey change it if it seems very thin or smells of gas. Do all of this outside.
Sid

 

You probably won't need any parts other than a can of carb cleaner, a q-tip, and a new needle. Leave the carb on the engine if you want, clamp the fuel line shut, remove the bowl, remove the needle, clean the seat area with a q-tip soaked with carb cleaner. If the carb is gummed up with varnish, you might them decide to remove it and clean it better, otherwise, give it a quick clean up and put it back together. This probably fixed the carb leak, but now you'll have to change the oil because there is gas in it too. Drain it, take the spark plug out and turn the engine by hand. Gas will shoot out the plug hole, so be sure to do this outside and make whatever provisions for safety you need. You may have to crank the engine with the starter and the plug out to get the last of the gas out. Be sure the plug wire is out of the way and not able to spark on anything (this makes a heck of an explosion/fireball with all the gas blowing out of the hole). Refill the engine with oil, check for leaks periodically, and you should be good to go.

 

sidny and cheese,
Thank you very much for your responses! I will definately consider the fuel shut off - not as a 'fix' but as a preventative measure going forward. I still plan to take the carb off the engine - I figure its just easyer for me to work on it on the bench. Do you think I should try the 'polishing compound on a q-tip' in the seat? Also does the solenoid hold the bowl on? Can I remove it by hand or will I need a thin wrench?

Thanks again
Paul

 

It should just take a 1/2" wrench to loosen the solenoid. Unless the key switch was left on, there should not be any way for fuel to seep into the crankcase.
Could just be a low or weak battery on the cranking issue.

 

I suppose that is possible as I have not actually pulled the spark plug out and/or tried to crank the engine over by hand. But from the amount of gas that saturated up into the air filter I have to believe alot of gas went down into the cylinder. I will look into that.

 

The polishing compound probably won't be necessary... that's just for worn and tarnished seats that don't want to seal even when you replace the needle.

The solenoid doesn't keep the gas out of the engine when the needle leaks. It comes up though the bowl vent and every other place it can find to enter the throat of the carb.

 

Thanks everyone for the responses!

Cheese,
I did alot of searching on this site for threads having to do with carb flooding, etc. Many had to do with this particular type of carb (Walbro LMT). I saw in a post of yours where you helped a fellow out who had a different type of carb with flooding problems and the problem turned out to be a clogged bowl vent. So my question is can a clogged bowl vent on a Walbro LMT cause the problem I have? Where - exactly - is the bowl vent on a Walbo LMT?

Thanks in advance
Paul

 

The bowl vents into the carb throat. I doubt it is clogged. I almost never see that as the problem but you can blow carb cleaner through the holes where the choke closes in the throat of the carb and the cleaner will come out in the bowl area near the top. This would indicate that the bowl vent is clear.

 

Cheese,
Thank you for the reply!

I will check the bowl vent and be sure it is clear when I get the carb off and clean it down.

BTW I just was checking the wrench clearance for the solenoid and my standard Craftsman 1/2 wrench is too thick to fit. And my ignition wrench set only goes up to 7/16. Looks like I need a 1/2 ignition wrench and Craftman only sells them in a set ($25!). Ugh. I guess my toolbox is gettin some more wrenches.

 

I you have a Harbor Freight in your area they have pretty good stuff(lifetime guarantee) for cheap by comparison. Have a good one. Geo

 

Just grind down a cheapie from the auto parts store.

 

That actually sounds quite appealing to my wallet.

Here is the patient (still on the engine):





Ill post more when I get the carb off and the bowl removed.

 

OK,
The carb is off and partially disassembled:

Air filter housing removed, linkage shown


A bit of [gentle] twisting and [quiet] cussing to get the linkages off


Solenoid off with ground down wrench (checked solenoid operation once it was off the carb)


No crap in the bowl (basically no deposits/varnish on any internal surfaces)


Float has freedom of movement


Float had no fuel in it, needle tip has small witness line it it where it contacts the seat (can see using an magnifying eye loop)


Confused about the fact that the seat is above flush. Everything Ive read said the seat is installed flush to the carb housing (factory carb, never disassembled)


Waiting for replacement parts Ive ordered from Jacks Small Engines


I pulled out the spark plug and turned the engine over by hand (blower housing/cover removed) to verify that its no longer 'hydro-locked' as it seemed to be when I first found the leak. Minimally Im replacing the needle, bowl gasket, fuel filter, fuel hoses from tank to carb (the one between the filter and the tank is 15 years old), and Ill clean up the seat with a q-tip. Id like some input on that non-flush seat. Also is there a simple way to 'bench test' the needle/seat seal before completely re-assembling the carb and putting it back on the engine?

Thanks everyone!
Paul

 

You can either make shift a gravity tank from a small fuel can or safe bottle with a piece of fuel line, or you can use the fuel line from the mower.
Reassemble the carb and without mounting it on the engine, fashion a way to keep it level and attach the fuel line. I usually give them at least 30 minutes with no signs of leakage before I determine it safe to install.

 

Don't worry about the seat... it's correct. The varnish on the needle and seat are probably the problem, and cleaning them may be enough to fix it. Replacement of the needle wouldn't hurt though.

 

Hi all,
Sorry for the delay. Ive had some other issues going on the last few weeks so I could not get to the tractor.

All my parts came in and I ended up replacing the needle, carb-to-bowl gasket/o-ring, and the o-ring between the carb and the air filter housing. I also cleaned the seat with a q-tip and there was a bit of crap on that seat. I wasnt sure how tight to put the solenoid back on (didnt want to crush the bowl o-ring) but it felt like the was a positive stop on the threaded part that sets the crush depth. I also replaced the 15 year old tank-to carb fuel line, replaced the fuel filter, and installed a B&S fuel shut off. I also changed the oil assuming there may have been some gas that got in it and installed a new air filter (I would have done those things in the spring before first use anyway). Once back together it started right up and ran well - right at 3180 RPM (no load). Im going to close that fuel shut off after each time Im done with the tractor to try to take the tank fuel load off that needle/seat.

So I hope Im good for at least a few more years. The tractor is a 1996 and I installed this engine in 2005. The engine currently has 154 hours on the Tinytach meter. The 15 yo hydrostatic transmission is leaking and that may want attention soon so too but Im hoping I can get a few more years before it needs a teardown.

Thank you to all that helped!! It is appreciated.

Here are some of pictures:

New parts (more that I needed but didnt cost that much):


New needle on the right (orange, not sure what the different material is):


Carb all back together and ready to install. Im glad a bought a new bowl gasket/o-ring as the old one (in the background) was pretty hardened:


Re-install linkage:


Carb bolted up:


All new fuel hose with new filter and shut off:


Hopefully ready for another season (yes, I plugged in the solenoid wires):