Mower starts then immediately dies

[reitz]

Hi:

New here. I have an older Murray 21" lawn mower (1993 vintage) with a Tecumseh 4.0 HP engine. The Murry model number is 21673x92a. It has run fine for almost 30 years but started an issue this season. It starts right up on one pull then dies immediately. After that one start it won't start at all until the plug is removed and cleaned from unburnt gas. It seems to have been slowly misbehaving over the last year or so. I tried the following: new plug, fresh gas, checked kill switch which is working fine, tried loose fuel cap in case vent not working. I would like to check ignition coil. Took it off and Ohm reading from kill switch terminal to ground is ~ .25KOhm, Ohm reading from plug terminal to ground is ~ 4KOhm. Not sure if those readings are in range or not. The coil has this number on it: 3064, I searched current coils for sale on Internet but that number does not come up. Any thoughts what to check next and where I could find a 3064 coil if that might be the issue? Thank you.

 

[sgkent]

It starts right up on one pull then dies immediately. After that one start it won't start at all until the plug is removed and cleaned from unburnt gas

sound rich so I would make sure the choke is off and try it once with the air cleaner off. In which case if it then runs replace the air filter. Sounds like it is too rich so you have to figure out why. Check the oil to see if it smells like gasoline, is higher than it should be, or is thin from gasoline.

Possible things that come to mind:
* malfunctioning choke
* dirty air filter
* sticking carb needle or sunken float

 

[reitz]

Thanks for the input. As far as I know there is no choke or fuel float. Just a slow to fast fuel lever. I did try with air filter removed and same result. Also don't know if there is a carb needle. It's a model that has a rubber button primer that you're supposed to press 3 times and then pull the cord. I'll check where the rubber hose from the bottom of the fuel bowl attaches to the inlet to the cylinder. There might be a metering device there that might be suspect.

 

[sgkent]

That model number did not come up in an online search for me although a "C" version with a B&S engine did. If that is it, it is likely that at 30 years old the carb is worn out or needs rebuilding. I'd take it to a local shop, especially because at that age you may not be able to find the original parts, and if substitutes are needed, it will require someone with some knowledge and experience as to what will work. Just my 2 cents. Maybe someone with access to older parts manuals that what are online may come along and offer other suggestions. The original owner's manual may have a parts list in it too. Online nothing seems to go back beyond 1974.

 

[reitz]

Right, it's an old mower (purchased 1993). The engine is Tecumseh. The original manual that came with it listed these engines: TVS90, TVS100, ...105, ...115, ...120; TVXL90, TVXL100, ...105, ...115, ...120. It didn't really tell me which one was in my mower and the sticker on the engine has long since worn off. I'll keep hunting. If nothing else it's a hobby of mine to make old things work again

 

[bertsmobile1]

The Tecumseh engine repair manuals are all over the web for free
Down load one & read it
From what you have said that should be your starting point
There are enough photos &drawings in the manual to work out which engine you have
If you are really stuck the carb has a number cast into the side and if you post it then those with dealer network access can cross check and come up with the engine number
No use of us telling you to check the carb float if you do not know what it is or where it is .

 

[reitz]

Well I took it apart enough to test the ignition coil and it appeared to be ok. I reset the gap cleaned all the gunk off all the parts that had to come off to get to the coil, put it all together and it decided to start right up. So maybe all the activity loosened up something that was stuck. I did find what I believe is the choke mechanism - a valve I can see when looking inside the carb that opens/closes when a rod on a spring outside the carb is pulled back and forth. However there is no manual cable connected to this mechanism and the throttle control on the push handle doesn't have an affect on this valve. The rod connected to this valve is attached to a lever and spring that pivots on half moon shaft that if turned caused the valve to open/close. That shaft goes inside the engine. I'm wondering if it is heat activated and possibly opens after the engine warms up.

 

[VegetiveSteam]

I removed part of my post as I see those questions were answered above.

When did it last run correctly?
Can you keep it running by pumping the primer bulb?

Some primer bulbs have a vent hole right where you put your finger when you prime it. Others do not. If yours doesn't and the primer bulb is ripped or has a hole in it start by replacing the primer bulb. If it starts and runs fine for a second or two there is nothing wrong with the ignition module. That is one thing Tecumseh was known for, their almost never failing ignition modules.

 

[Cfs]

I know this is an old thread. But I have a similar problem with a TVS 120.,,I replaced the primer ( the old one broke off) with a primer with a hole in the center. Now it starts and dies I

figured out if if plug the hole in the primer right after starting it …it continues to run. Seems like there is pressure flowing from the carb back to the primer. When I run it plugged the primer seems to inflate somewhat. Any thing you can advise me as to what you found

CFS