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MTD Yardman rototiller starts but won't run


Markswife's Avatar
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08-14-09, 12:59 PM   #1  
MTD Yardman rototiller starts but won't run

We just got a used 5.5 hp MTD Yardman rototiller.
model # 21A-394-401 Serial # 1C150k50447
with a Brigg's and Stratton engine #110402 0161 E1

It had been sitting for a while with old gas and oil in it. My husband changed the oil and put new gas in it. It still wouldn't run (started and stopped). So based on some of the other advice I could find here, he cleaned out the carburetor. Some of the gaskets were broken. So we got a carb kit and he replaced those. He cleaned out a hole on the bottom of the carburetor that was completely clogged. At night he could see the spark plug lighting. But, it still won't stay running.

Any other advice/input would be appreciated. Thank you.

 
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Airman's Avatar
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08-15-09, 05:17 AM   #2  
I suspect the carburetor needs a more thorough cleaning. Remove the welch plug and clean the transition (fuel) ports under it. Pick up a welch plug 694468 (3/8 Diameter) at a local shop.


This link should help with cleaning and welch plug removal and installation:

What are the procedures to follow when overhauling the carburetor?

 
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08-15-09, 09:03 AM   #3  
Thanks! I will pass on the info.

Last night my husband installed a new air filter and new spark plug. It ran longer--about 5 seconds before quitting. So, hopefully these instructions will help. Also, on the instructions it talks about a high altitude adjustment. The info I can find says we live about 4400 feet above sea level. Do we need to make an adjustment at this altitude?

 
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08-15-09, 08:25 PM   #4  
still doesn't work - gaaaaa!!!!!!

I replaced the welch plug and re-cleaned the carburetor according to the instructions on the link you provided. I used carburetor cleaner to re-clean everything. It still won't stay running.

It may be time to have an expert look at it. I'm out of ideas. I'm thinking there's an air leak somewhere, because it will run up to 5 or 6 seconds when I let it sit for about a minute.

I can't see how there would be a leak in the carburetor because I replaced all of the seals, gaskets, etc. and tighted everything down really tight. I also replaced the hoses that go from the fuel tank to the carburetor.

 
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08-16-09, 07:56 AM   #5  
You apparently are having a fuel delivery problem. Possibly the float needle is sticking and not allowing fuel to flow freely into the bowl or something is obstructing fuel flow between tank and carburetor. Remove the bowl and see if the float moves freely and if there is free flow of fuel through the needle. Have a cup available to catch the fuel and do this outdoors away from an ignition source.

You did assure the holes behind the welch plug were open and clean?

 
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08-16-09, 08:05 PM   #6  
Also:
-Old gas will leave "Varnish" in the gas lines and carb. It will need a complete tear down and cleaning.
-Check the float level on the carb, is it sticking? Turn carb up side down and place an 11/32 drill bit between the base and float. That's the height it should be at full of fuel when installed.
-Ensure all jets are in good condition - main / float etc... no warping,nics, or blunting of the needle.


Last edited by Square Head; 08-16-09 at 08:06 PM. Reason: spell
 
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08-19-09, 08:18 PM   #7  
Thanks for your suggestions!

Well, my husband checked the float needle. All appeared fine with that. All the holes are open and clean. It was still stopping shortly after starting it up. My husband thought that if he could get it running that it might clean itself out. So he kept starting it over and over. It got to the point where it was running, very roughly, for about 1 or 2 minutes. He kept this up for awhile. It seemed like it needed to store up a little gas in order to start inbetween running times. Then, he let it sit for about a half hour, and it would only run for 3-5 seconds again. So, he called it a night.

Any more suggestions for us? Should we buy a complete carburetor replacement?

 
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08-20-09, 07:20 AM   #8  
Is the fuel tank located higher than the carb (garvity fed)? or lower (fuel pump)? Is there a any valve on the bottom of the tank that should be opened more? Screen in the bottom of the fuel tank that's clogged with gunk? Fuel lines clear?

 
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08-20-09, 10:36 AM   #9  
Is the fuel tank located higher than the carb (garvity fed)? or lower (fuel pump)? Fuel tank is higher, so gravity fed.

Is there a any valve on the bottom of the tank that should be opened more? Screen in the bottom of the fuel tank that's clogged with gunk? I don't know. I will ask Mark.

Fuel lines clear? Mark replaced the fuel line because it had cracks. So, it is brand new and should be free and clear.

 
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08-20-09, 07:30 PM   #10  
I don't see any valve, but I'll check to make sure there's nothing that's clogging the fuel.

I disconnected the fuel line from the carburetor and then I turned the fueld switch to "On". Gas seemed to flow out nicely. But it's worth looking at.

 
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08-20-09, 07:57 PM   #11  
If the fuel is running out of the line well, the problem is likely between the float valve and the inlet to the carburetor.

Take off the carb bowl and let the float hang freely and see if fuel flows well past the float valve. If it doesn't, take off the fuel line from the inlet fitting, remove the float and float valve and blow the passage out with carb cleaner. Don't put the bowl back on until you have a good flow past the float valve.

 
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08-24-09, 04:40 PM   #12  
marbobj

Thank you for the suggestion.

I checked what you said and the fuel passed through just fine. I went ahead and sprayed carb cleaner through it.
It still doesn't work.

Here's one thing I discovered. By using starter fluid I could get it to run for a longer period of time. About 5 minutes (not constant starter fluid, but just a couple boosts.).

It ran really rough, but if I pulled the handle down so that the tiller was leaning far back it would start running very strong. Like it should all the time.

But after a little while of doing that, I would see a bunch of smoke coming out of the exhaust. This would continue for a while, but then clear out after a minute or two.

Does this help at all?????

 
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