have to pull choke to get power and engine at constant speed

[cgambino1018 21]

newbie here..

have a 312-with a magnum kohler engine and warlbro carb.

I was cutting grass two weeks ago and then the engine just started stalling and sporadically idling.. I have now somewhat control by pulling the choke 1/2 way out.

I have rest the carb screws using the below formula:

-high idle fuel  - 1  1/8 turns from bottom

-at low throttle set low idle speed adjustment screw at 1 3/4 turns from bottom

-after 5 min of warming up turned low idle fuel  1 3/4 at 1/2 throttle. 

 

when this happened I had filled the tank with premium gas ...not sure this matters.

 

also just strayed water in to carb for a quick cleaning... no difference..

 

All help is appreciated.

 

Chris

 

[953 nut 51,626]

Chris, welcome to the square. Have you replaced the gas filter? Another thing to consider is the gas cap vent, if the problem comes back try opening the gas cap, if that clears the problem replace it with a new one; worked for me!

 

[cgambino1018 21]

i am pretty good with the gas filter.. usually every year and 2 years max and its replaced..I do use a large gas filter.. its about 1inch x 2 inches and its never full of gas.. there is a small stream down the lower side of it. should I try  a smaller filter?

 

the gas cap is about 2 years old.. replaced the old b/c it rusted up and it wouldn't give the right level of gas in the tank.

 

i will try loosening the gas cap and running it for a bit after that  i will go to a smaller gas filter.. I have a small inline one for my daughters Polaris 90 ATV. 

 

Thanks for all the help.

Chris

[sorekiwi 761]

My 520 played up in a similar way on Friday.  A new filter and a carb cleanup did nothing, so I blew backwards throught the "T" fitting in the bottom of the tank.  The strainer must've been clogged, it ran great after that.

[KATO 115]

 and it's also possible the premium fuel has a good detergent package that loosened up some crud and sent it through your system. A good cleaning may be in order.

[WH nut 553]

The Carb setting is just a base starting point. Try backing out the high speed to see if it improves. You have a either a fuel delivery problem or crude in the carb. You may be able to pull the bowl and clean it to get it going

[meadowfield 2,545]

We had that last week on a c121, fuel pump was packing up and engine starved of fuel.

[Derrick 0]

Chris,

 

I'm a newbie here myself. I'm also having similar issues with my 414-8. It runs strong in colder weather without issues. However, once the hot summer months gets here, the tractor wants to return to idle after a half hour or so of mowing. I can somewhat control this for a short time with the choke, but it eventually gets to the point where I shut it down and let it cool for a while. Then I can continue mowing for another half hour or so before it all happens again. I use premium gas with Marvel Mystery Oil and Sta-Bil if it's going to sit for a while. I've changed the air filter and spark plug and have made sure the carb is dialed in. I only seem to have an issue when the throttle is wide open. I've tried mowing with the gas cap loosened, but it's not helping much. I think I'm going to replace the fuel line and go from there. Sounds like we have the same issue. If you find the right fix, let me know. I'll be sure to do the same. Thanks and good luck.

 

Derrick

[Marv 845]

Chris,

You might consider replacing the fuel pump with an electric pump. I had the same problem and electric pump cured it. I really like the elect pump so I installed one on my C111 and plan to do the same to my D200.

Marvin

[cgambino1018 21]

All,

thanks for the ideas.

today I swapped the gas filter and blew air back to the gas tank..instantly fuel flowed down to the gas filter and it filled.  prior to this it was just a small stream.

I then took off the tube from the gas filter to the fuel pump.. i noticed it was worn in one spot.  i didnt have replacement hose so I wrapped it in electrical tape for now.

 

I got  it to start right up. i was able to put the choke in  but in order to stop the back firing I had to the move the high idle fuel out about 3 - 3 1/2 turns.   the book say 1 1/8 as a starting point.

i am thinking next i replace the gas line and then test again.  what do you guys think.

 

Also I checked and cleaned the spark plug and it was pretty white.  

 

Thanks

Chris

[wheeledhorseman 573]

Difficult to test without substitution but reading the symptoms and partial solution / improvement achieved so far my money (like Meadowfield's) would be on the fuel pump being on its way out. When that's the case they can also sort of work when cold but ability to pump fuel dimishes as they get hot and setting the mixture becomes difficult as, like pulling the choke out, you're trying to compensate for a different fault. Just my thoughts on the issue.

 

Andy

[wallfish 15,918]

Have you cleaned the carb since having this problem?

If not, you may want to start with a thorough carb cleaning. It certainly won't hurt anything to have a nice clean carb, even if the problem turns out to be something else.

When there's a need to apply the choke for the engine to run correctly, in essence, you are adjusting the air flow to match the amount of fuel being delivered. More choking means less air to match less fuel. Opening that needle is allowing more fuel but it shouldn't need to be opened that far. My guess is a dirty carb.

[cgambino1018 21]

the carb was rebuilt about 3 years ago.

I did spray water into it over the weekend.  Should i spray carb cleaner now?

I will clean the fuel pump over the next few days. and get the gas line replaced.

also will take the bowl off and see whats going on in there.

 

Thanks

Chris

[wallfish 15,918]

You should remove the entire carb and give it a thorough cleaning. Separate all the little parts and spray them. Spray through all the little holes in the body and the needle. It's even better to soak them over night but if you don't have a gallon can of carb soak cleaner, spraying them will probably do it. Just spraying into a mounted carb won't really do anything. 3 years is a long time with the horrible gas they sell these days. You probably don't need to rebuild it, just clean it thoroughly. If you haven't pulled the bowl in 3 years, just wait until you see what's in there. 

 

Spraying water into it could be part of your problem. That's an old timer's trick of steam cleaning the combustion chamber to clean out the carbon and not a way to clean a carb. It's done with the engine running to turn the water into steam and in theory, steam out the carbon build up.

[cgambino1018 21]

tonight i took the fuel pump apart... everything inside seemed fine.. clean it and put back together.. turn the engine over a few times and it squired out gas.  I think thats ok.

i then took the bowl off the carb.. plenty of dirt in there.. sprayed it down carb cleaner, checked that the pin by the hinge is sliding up and down  and put the bowl back on.  

i did notice there is seal on the bowl.. so i closed it real tight.  

 

started it up and same problem... have to pull chock 1/2 way to keep a steady idle..

 

should i just order a new carb or a repair kit?

 

All advice is appreciated.

Chris. 

[wallfish 15,918]

Please read my previous post. Cleaning just the bowl isn't going to help that much. Some of that crude you found in there made it up and into the passage ways of the carb and it's restricting the amount of fuel it needs to properly mix with the air intake. A rebuild kit isn't going to fix anything unless you thoroughly clean it anyway. If you do order a new carb, I'll buy that old broken one!

[wallfish 15,918]

Another problem with that carb could be excessive play in the throttle shaft at the top of the carb and/or air leaking past the mount gasket. While it's running, spray some carb cleaner around those areas and you shouldn't hear any difference in how it runs. If it's sucking air past those points it will suck in the carb cleaner and you can hear the change. Do it with the air filter on to limit any cleaner entering the front. I still think a good cleaning will help. Wouldn't hurt to drain the gas and fill up with new gas from a different can.

 

Here's a good read on the carb which should help. Lots of good info!

  

[cgambino1018 21]

sprayed around the carb with starting fluid and carb cleaner when it was at a constant idle and not change in revs.

on a side note the outside of the carb is clean now

 

how do I check excessive play in the throttle shaft?

 

also i ordered a carb rebuild kit today.

[wallfish 15,918]

You just did. If it had excessive wear, it would have sucked in the fluid when you sprayed around it. That's a good sign!  

[C-101plowerpower 1,605]

better pull the carb and clean it. if you have acces to a ultrasonic cleaner pop it in there, when the carb is cleaned use an air compressor and blow through al the holes you see, put it back together and try again, if this doesn't help try to borrow a carb from somebody whose engine runs fine. if you still have the problem it isn't the carb

[Coadster32 793]

There are really small holes in these carbs that get gummed up pretty quicky. Some of the small holes in the jet needle also get clogged. All of these holes are pretty importaint. If you do rebuild it with new gaskets and don't pay much attention to the tiny holes, you could just be wasting your time, (and money).

 

If you think the fuel pump is suspect, you could also just gravity feed it to find out pretty fast. (Although to me, it does sound like a dirty carb.)

[JimmyJam 516]

There are really small holes in these carbs that get gummed up pretty quicky. Some of the small holes in the jet needle also get clogged. All of these holes are pretty importaint. If you do rebuild it with new gaskets and don't pay much attention to the tiny holes, you could just be wasting your time, (and money).

 

If you think the fuel pump is suspect, you could also just gravity feed it to find out pretty fast. (Although to me, it does sound like a dirty carb.)

I agree. Those tiny holes have to be clear and free of dirt. Seafoam has a carb cleaner that I use and works!

[tunahead72 2,337]

sprayed around the carb with starting fluid and carb cleaner when it was at a constant idle and not change in revs.

...

 

how do I check excessive play in the throttle shaft?

 

...

 

You just did. If it had excessive wear, it would have sucked in the fluid when you sprayed around it. That's a good sign!  

 

I think John's right, your throttle shaft is probably fine.  But to be sure, I would repeat your spray test while jiggling the shaft back and forth, maybe try different engine speeds as well, see if any of that makes a difference.  If you do have excessive play there, you'll go nuts trying to adjust your carb, because it will essentially adjust its own mixture as you change throttle settings.

 

Don't forget to spray around the gasket where the carb mounts to the engine, that could be leaking also.  You should plan to replace that gasket anyway, and it may not come with your rebuild kit.

 

I think a good thorough carb cleaning will work wonders for you.  If you haven't done one of these before, just be patient, and take lots of photos.  I'm getting ready to do one of mine, a K241 on my C-105 -- very similar symptoms, it has a sweet spot with the choke slightly closed where it runs real nice, but it's just time.

[WVMountainMan 6]

Sure sounds like a dirty carb to me. I went through this on a 416H recently that had been sitting around for a while. I got the engine started and kept spraying Sea Foam Deep Creep into the carb, really concentrating on using the red spray tube that comes with the can of spray, spraying down into the 2 little holes down in the carb. Each time I would spray it, the engine would about bog completely down, belch out a cloud of white smoke and level out just a little bit more each time. After a while the ol girl started idling like a new one and it now runs just fine.

[MalMac 1,328]

Like all the prior post, clean the carb completely. Disassemble the carb by taking the bowl off. Remove the float, let the pin drop down and inspect it. Look at the rubber on the end of it to see if it's not worn or messed up in some way. Pull both the needles out. On the main needle the long one there will be tiny holes in it, They have to be clean. Hold it up to a light to make sure you can see through them. Check the needles to make sure they are not bent or have any messed up tips. Take the carb body and soak it in carb cleaner overnight or use a can of carb cleaner and a small wire to spray, poke and prod any little orifice, Todays gas is junk and it does not take very long for particles or gumming to clog the very small passages and holes on your carb. Once you do that you should notice a difference. All of this will do no good if you have got junk in your gas tank or old gas line that is deteriorating from the inside letting small particles of rubber float through. Using a lot of gas additives will cause rubber gas line to start deteriorating from the inside out over time. One of the popular gas additives Sea Foam will do this. It's great stuff but over a period of time it will eat rubber hose and gaskets.