Flooding carb in cold weather

Mon Dec 31, 2012 9:33 am

It did it again, once the temperature dropped long enough below freezing. Battery charged and oil pan heated for several hours. Out to start and first open gas line, then choke out, throttle forward. Turned over, no start. On and on, varying choke and throttle. Finally a cough, a weak start that wouldn't take. Gas dripping out the bottom of the carb, and when turning over the engine I even see fuel coming out at the gasket line. A regular soaked spot in the snow on the ground below the carb.

Had earlier assumed that intake manifolds just too cold to keep fuel atomized on its trip up to the spark plugs. Still think that. Assume flooded situation, so wait. Come back and maybe a cough or timid start and silence. Shovel beckons for a snow clean up.

Over the summer: a carb rebuild--new needles, float checked out, new gasket, etc.

In warmer weather she starts up without any hesitation. This is why I think a heater plug inserted in the water intake elbow will work.

Tractor sits in a cold barn, a bit protected.


Re: Flooding carb in cold weather

Mon Dec 31, 2012 9:46 am

I'm not the world's biggest carb expert, but that float has to be perfect, plus, if the tractor is not starting because of other thing (less-than-perfect timing, spark, plugs, compression etc etc) what happens is, in the cold, those little problems become bigger problems. Gas is being drawn up while you're trying to start it, then when you stop trying, it drains back into the carb and drips out. Just because gas drips out, the real problem might not be the carb.

I'm going thru the same thing with an H.

Re: Flooding carb in cold weather

Mon Dec 31, 2012 10:04 am

Start with; compression tests, valve tappet adjustment, air cleaner, and ignition system. Carburetion issues, last.

Re: Flooding carb in cold weather

Mon Dec 31, 2012 11:20 am

Make sure you have a good BLUE spark at the plugs, also check the air cleaner bowl and make sure it does not have water on top of the oil that was turned in to ice cutting off the air, you can just pull the air tube off the carb also to bypass it for a quick check to see if it runs

Re: Flooding carb in cold weather

Mon Dec 31, 2012 11:39 am

the gas running out after choking is normal. that is just the extra gas from choking that is running out. as to the non starting. you are getting gas. I assume your getting good hot spark. only other thing is compression. Low compression will cause hard starting in cold weather. usually will cause plugs to frost up. compression below 90lb in cold weather will create hard starting. the colder it is the harder it will start. I have 4 cubs with rebuilt engines that hold 135 LB compression or better. they start easy in cold weather. I have one I use all winter that starts very good at -10 deg.

Re: Flooding carb in cold weather

Mon Dec 31, 2012 8:29 pm

Plugs are easy to gas foul in the winter.. choking coupled w/ poor vaporization because of the cold can soak a plug in a heartbeat... you might just try a new set and see what happens.. not that expensive and not a bad preventative maintainence thing to do. Its a common problem with older tractors that don't get used like they used to. They were designed with long hours, heavy pulling and higher engine temperatures in mind. Most are worked far easier today than they ever did in their working life so the engines just don't get up to temperature like they should, thereby burning off residue on the plugs.

Re: Flooding carb in cold weather

Tue Jan 01, 2013 9:10 am

Thanks, everyone. As it turned out, the weather yesterday warmed up to higher 20 degs. F, and the Cub started. Come summer, I'll check into all of the options suggested.

Re: Flooding carb in cold weather

Tue Jan 01, 2013 11:29 am

Once it is above freezing, remove the plug in the bottom of the carb and drain it, also empty the sediment bowl. You may have some ice in it causing problems. A little Sea Foam or deicer in the fall doesn't hurt either.

Re: Flooding carb in cold weather

Thu Jan 03, 2013 6:04 pm

Try leaving the choke in when you first crank, then if she doesn't start on the first turn or two, start pulling the choke rod as she cranks. I used to have some trouble starting in cold weather starting with the choke closed. Someone on the forum here suggested not choking her right away. I have had much better luck with the new method.

Re: Flooding carb in cold weather

Fri Jan 04, 2013 10:27 am

Also instead of setting the choke and cranking away, give it quick "blips" of choke.

Re: Flooding carb in cold weather

Sat Jan 05, 2013 6:57 am

HI Mike and Matt -- I think you guys are on to it. Yesterday at a balmy +30F, the following:

Pull 1: full choke, no start
2: just a bit of choke, no start
3: a bit more coke: wanted to start
4: ignition with a wee bit more of choke. Followed by some replowing side of road at mailbox where town plow had made life tough for the Mail Delivery folks, the walkway where drifts were building up.

Next time it is very cold will try 1: no choke, 2: crank while moving choke lever in/out which is what I think Matt refers to by "blipping."