Craftsman Lawnmower won't stay running after I...

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  #1  
Old 07-07-12, 07:22 AM
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Craftsman Lawnmower won't stay running after I...

1. waited four weeks and replaced the carb (Tecumesh)
2. Used new fresh fuel
3. changed oil
4. changed spark plug
5. removed carb to check gaskets.
6. ensured choke was open

It starts up on a first crank but won't continue. If I use starter fluid, I can keep it running but of course it wants to die. checked fuel bowl and it was full...not sure what to check next.
 
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  #2  
Old 07-07-12, 08:40 AM
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Post the mower and engine model numbers so we know which one you have. Have a good one. Geo
 
  #3  
Old 07-07-12, 09:20 AM
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I am not a professional small engine mechanic but but I seem to be able to get almost any machine running as long as there is compression. I guess that's why a lot of people keep bringing me machines to fix and almost always it is a methanol/gas caused problem. Usually it's the fuel line, primer bulb or some gasket that has been ruined by the methanol. That or they let it sit all winter long with gas in it.
Here is what my experience has taught me.
The gas/methanol thing is really messing up a of of machines. For myself, I buy mid-grade gas and use stabilizer but even with stabilizer I don't keep it too long. Three weeks, tops. I could probably keep it a lot longer but I never have fuel related problems. Ever. And for pre-mix, if I can't remember when I mixed it, I toss it.

New carburetor or not, here is what I would do.
First, let me ask, has it been a while since you've run the mower?
Will it keep running with the choke partially closed?
Maybe with your hand over the intake does it keep running?
That says that it is taking a lot of vacuum to suck fuel through your carburetor because of a plugged passageway somewhere. You say that the bowl fills up normally?

These are some of the things I would be doing.

You've dumped the bowl and cleaned it? There might have been some bits of crud in the fuel line or tank large enough to immediately bugger your new carburetor up.
While the bowl was off and the carb was attached to the engine and fuel line, did fuel flow freely from the tank.
Turn the carb over , remove the rubber bowl gasket and spray the bejeezus out of it with carb cleaner. Especially the jet, inside of that post in the center.
Try not to spray carb cleaner on rubber gaskets. They are never the same after that.
I'm not sure if your carb has them or not but I always remove the low and high mixture screws and clean them and the hole out.
Look for damage to the tips of the screws and when you put them back in, don't screw them in too tight. Try to count the number of turns when you remove them and put them back the same way.
Check the fuel line carefully. Is it all soft or cracked? Methanol is a solvent and it will attack fuel lines and gaskets.
Is there a fuel filter? Is it allowing fuel to pass through?
As an aside, I don't try to keep an engine running on starting fluid. Most of them do not contain any lubricants and I'm always afraid of damaging the engine that way. I'm probably wrong on that one but better safe than sorry.
Well, that ought to keep you busy for a while. I have a chipper in the shop to get running and then a John Deere to go pick up and it is like 200 degrees out there.
 
  #4  
Old 07-07-12, 10:15 AM
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Craftsman model 917.382781

Engine model # 143.954502

And yes fuel flows freely nicely from hose leading from tank when removed though the hose could use replacement.
 
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Old 07-07-12, 11:38 AM
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New carburetor or not, here is what I would do.
First, let me ask, has it been a while since you've run the mower?
Will it keep running with the choke partially closed?
Maybe with your hand over the intake does it keep running?
That says that it is taking a lot of vacuum to suck fuel through your carburetor because of a plugged passageway somewhere. You say that the bowl fills up normally?
Put my hand over the intake and was able to set it up so it would stay running. Take it away...and it died. Did this a couple of times.

So what's next? How many passageway's can there be?

throttle is wide open. Several years I took it in for a tune-up and when I got it back, the throttle mechanism was wide open. I've played with the linkage but its run with it wide open so don't believe that is contributing to it dieing.

What about the breather tube? Looks like it needs a cleaning.
 

Last edited by hunt4cleanair; 07-07-12 at 12:50 PM.
  #6  
Old 07-07-12, 02:38 PM
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OK, then the filter (if you have one) isn't clogged. But with the carb installed minus the bowl and fuel line connected, hold the float up (Lightly, not too much pressure or you will damage the needle or seat) and the gas should stop. Lower the float and it should flow.
 
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Old 07-07-12, 02:40 PM
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The bowl nut on this carb is the main jet, the tiny hole near the top of the threads is usually the problem, I clean it with the wire from a twist tie. Have a good one. Geo
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Old 07-07-12, 02:49 PM
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If you hold your hand over the intake and you can get it to run, as I said, there is an obstruction and only a huge amount of vacuum can overcome it. We need to find the obstruction.

But before we do anything, turn your idle up, way up and see if it keeps running.

I'm going to check out the model numbers you gave and see what kind of carb it is. In the meantime, take the carb off again (you should be getting pretty good at this), remove the bowl and gasket and spray everything under there paying attention to the tube that goes down into the bowl. That is where the gas is sucked up into the carb. Another thing to check is the gasket between the carb and engine. If it is losing vacuum there it might not be able to suck the gas. Take out the two adjustment screws (counting the turns) and clean those out. We might have to remove the main jet to clean it but we won't go there yet.
Like I said, I am not a professional but I don't remember a breather tube ever causing this type of problem.
 
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Old 07-07-12, 02:52 PM
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I posted before I saw this post. I was going to look at the model numbers to see his carburetor. You are so right. It doesn't take much to clog that hole. If there was a bit of crud in the tank, even putting fresh gas in the crud could have gotten into the line and would have plugged that hole.
 
  #10  
Old 07-07-12, 09:01 PM
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Check the hole that Geogrubb showed a pic of. This is normally the cause of the problems you're having.
 
  #11  
Old 07-08-12, 10:27 AM
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and a hole down the centre of that nut needs to be clear.
 
  #12  
Old 07-08-12, 11:22 AM
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It runs!

And with great power...almost too much until I hit a high clump of grass but than mows on through it.

I removed the bowl, nut and needle. The old carb did not have an adjustable needle like this replacement. I commenced to bend a staple and clean out that litle hole. I than used carb cleaner and blew out everything except the gasket and float assembly. the float, when dropped did spew gas.

On start up, it ran weakly so I adjusted the needle. At first I choked it, engine died. I turned the needle out, started it and it started right up than at a low thottle level. I than adjusted it upward until the engine roared and than backoff a turn, left it and cut the freakin foot high grass.

I than it was a combo of crap in that needle hole and the needle adjustment. I now have to figure out the linkage. So those looking at the engine schematics with suggestions, feel free to post.

PS...and thanks to all for your patience, guidance and expertise.
 
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Old 07-08-12, 12:24 PM
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Success is a wonderful sound. Have a good one. Geo
 
  #14  
Old 07-08-12, 12:40 PM
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Here is a video that may help you with the linkage. Have a good one. Geo

how to tecumseh lawnmower speed and governor adjustments - small engine Davidsfarmison[bliptv]now - YouTube
 
  #15  
Old 08-12-12, 04:11 PM
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How many hundreds have you helped with this advice?!

More than 7 years after Cheese first posted the suggestion about cleaning the little holes in the fuel bowl, it's still helping people! I had my lawnmower loaded into the truck to take for repairs--but thought I'd give the internet just one look for a solution. Found an earlier thread on this site, and 20 minutes (and a hand full of gasoline) later, the mower was running for the first time in weeks. Thanks Cheese!
 
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