After carb rebuild, still won't start, Tecumseh 4.5 hp mower, Sears

[Davisrf]

Hi, it was flooding out throat, so I checked the float and it had gas in it. I put in a new (plastic) float, replaced the gas intake needle seat and injected carb cleaner thru all proper orifices. This carb is about 15+ years old, does not have any screw adjustments. I made sure that the gas intake needle that suspends from the float is seating ok and that the float is level. Also, I tested by blowing into the gas intake (where gas line attaches) and no leaks when float depressed and heard good flow of air when I
caused the float to raise up the needle . The bowel was reattached properly (the indented portion toward the needle valve.) When I try to start it, it runs for 3 seconds and dies. If I keep skirting gas into the carb throat, it will run. The screw that holds the bowel on is the type that has the 2 holes on either side, just under the screw head and one small hole near the beginning of the threads. This is NOT the type of screw that has openings in the nut head that is exterior to the bowl. Those holes and the screw itself are absolutely clean and open. Obviously I screwed something up in the process. I did n ot take out the main venturi when I cleaned all other aspects. But I blew carb cleaner up thru it from the bowl end. Your help is appreciated... the lawn is growing while I spend time trying to sort this out !!

 

[KennyV]

Welcome to LMF...

It sounds like you have the carb cleaned... The engine is running when it gets fuel..
The only other thing I can see from your description, Is there fuel actually flowing from the tank to the carburetor? :smile:KennyV

 

[Davisrf]

Kenny, Thanks for the feedback. The flow of gas from the tank to the carb is good , and the bowel is filling with gas. The float is level and the intake needle is seating properly because when it is depressed, no air flows when you blow into the gas inlet and when you open the needle up from the seat, air flows well when blowing into it. THe only thing I have not dealt with is the venturi tube. Do you think I need to remove that and check it for flow thru, if so, does it just inserted in their as a press fit? Just pull it out? Or does it twist out? I have alrfeady shot a flow of carb cleaner up that tube .
The whole problem started with flooding of the carb, and sure enough, the float had gas in it so I replaced the float, leveled it, cleaned all orifices in the carb, replaced the seat and needle. When it initially flooded it would take about a minute of running for it to flood out, now it won't even start unless I continually spray gas into it. So, possibly some particle has gotten up into the upper end of the venturi , where it seats. There is no way to see what is going on up there, but to remove the venturi and spray cleaner up there. But, if it runs OK by spraying gas down the throat of the carb,
does that say that the venturi and what it inserts into, is OK ??
Another question: what is a good mower to buy nowadays... is B&S still a good mower engine. I have worked on those also (I have 2 at rental houses I have) and they have much less parts involved in the carb, but I replace the diaphram about every season and a half as they fail....but easy to replace and not only a few bucks cost. I'd prefer a Honda engine but I think they only make mowers that self propel and I don't need that for small lawns. Thanks again for you help. Steve

 

[KennyV]

Steve those tubes are generally very tight fitting, press fit And then staked... I have never had any luck removing one ...
If you can get the spray tube into the opposite end... do you see anything spraying out the tube?

I'm not a big fan of Tecumseh carbs... I have always felt they leave a lot to be desired. But you have to work with what you have, so if it is blocked try compressed air into the throat of the carb... if its still on the engine do it while the intake valve is closed... That could push the obstruction back the way it came in...

The next time you have it running using fuel sprayed into the intake... cover the intake so the complete intake vacuum of the running engine pulls on that tube ... it may pull what ever is blocking it through...
I hate to think that small tube could get so blocked that you have to replace the complete carb. Give the above methods a couple tries before you try pulling the tube out...

When you had the carb apart,were there any pieces around the venture that may have gone together wrong... the venture principal is a very simple pressure drop suction principal, but the shape of the air passage in the vicinity of air flow is very critical... I have seen some that would not function correct if the air filter was not installed... they needed the additional restriction of the complete assembly to get fuel to pull up that pipit...:smile:KennyV

 

[Davisrf]

I will try your suggestions before trying to remove the venture tube. There is not way to spray into the other end of it without removing it. There was nothing foreighn in or around the end you can see which is at the float end. In fact, the whole carb was very clean inside. There were no removable pieces
around the exposed end of the tube that could be removed. The nut (screw with nut head) that holds the
bowel onto the carb has holes in it, as you likely know, the holes are inside the bowland they are completely clean so that the tiny amounts of gas in the bowl go thru those holes and up the tube.
When this engine is running ok it makes no difference if the air filter is on or off .
Will let you know what happens. Tnx again, Steve

 

[Davisrf]

Hi Kenney,

Your suggestion worked (block off carb while running ) but I am back to the original problem, but no flooding. Originally it would run for about 60 seconds then it flooded. NOw it will run for 60 seconds then quit. Wonder if that sounds familiar to you , if so what you think? Thanks, Steve

 

[KennyV]

It's going to be a fuel problem... Or might be a fuel/air problem... How is the gasket that is between the carb & the intake port... an air leak would cause it to lean out and quit... :smile:KennyV