Single Stage Tecumseh only starts on starting fluid - Snowblower Forum : Snow Blower Forums
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post #1 of 14 Old 11-17-2019, 06:10 PM Thread Starter
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Single Stage Tecumseh only starts on starting fluid

I have several 2 stroke Tecumseh single-stage 21" blowers and have cleaned up several and understand the carb. On one of them I can only get it started on starting fluid. Once it gets going it runs perfect and will even start without starting fluid if restarted within an hour of getting warmed up.

Here is what I have done:
New push primer bulb
New primer line
full carb clean - cleaned the main jet and other passages
new float gasket
checked float levels
fuel filter
new fuel line

I can see the choke butterfly close the carb opening.

I wonder if I am missing a gasket.

I am really stumped on this one. Any ideas what I may have missed?

Last edited by Mike Dee; 11-17-2019 at 06:16 PM.
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post #2 of 14 Old 11-17-2019, 06:43 PM
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I wonder if the primer isn't working as it should....
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post #3 of 14 Old 11-18-2019, 10:34 AM Thread Starter
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Yea, I think you are right. I made a mistake on another similar carb clean last night and think I may have figured what I did wrong - I could use some feedback to let me know if I am on the right page.

When I was cleaning a Tecumseh carb last night on another blower I cleaned it well then used my air compressor to blow it dry. I put the tip of the compressor attachment right onto the primer nipple and blasted it. I then heard something shoot off into the garage. I inspected the float area and realized I blew-out one of the tiny, round inserts which feeds into the float area - and must be the area where the primer passageway ends. I am pretty confident I did the same move on the blower I initially posted on which would not start cold w/o starting fluid.

If this small part was indeed blown out it would explain, like you suggested, that the primer circuit is not working as it should.

Agree? I will have to look on some schematics to see what the heck I blew into oblivion. Perhaps it's a brass jet fitting.
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post #4 of 14 Old 11-18-2019, 11:17 AM
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Hello Mike. Here is a link showing a typical two cycle Tecumseh carb.
https://outdoorpowerinfo.com/repairs...arb_640342.asp


You may have blown out the inlet needle seat (doubtful) in picture 16, the welch plug (pretty likely) in picture 22 or one of the O-rings for the emulsion tube, if your carb has one, in picture 18.


Is your spark plug wet or dry after trying to start it? Low engine compression could cause hard or no start conditions and the starting fluid, being more volitale, could be the reason it starts and draws in more gas to continue running???

Toro 8/24 (38080) 1989
Toro 721-QZR (38743) 2015 (Hemi Predator Power)

Experience is something you don't get until just after you need it.

Last edited by Grunt; 11-18-2019 at 11:23 AM.
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post #5 of 14 Old 11-18-2019, 11:51 AM Thread Starter
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Great link! Can't believe I have not seen that before. I will save it for reference for sure!

You are correct, after reviewing the pics I did blow out the needle seat. It was leaking gas upon assembly and I thought the float level was off. I will order some new seats and give it a try. I will also look at the plug to see if it's wet.

I wonder, with the needle seat gone would THAT be the reason for only starting on starting fluid?

Here is the pic of the carb. You can see the missing seat at the 11:00 position.
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post #6 of 14 Old 11-18-2019, 03:33 PM
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That should be a rubber Viton needle seat that you blew out.
It will flood the engine without it and with too much gas, fuel level too high in the bowl, it will not mix with air properly to start the engine. It is like dumping raw gas down the throat of the carb and is too rich to ignite.
The fuel droplets will be too big to ignite. If you start the engine with starting fluid, then the air rushing through the venturi of the carb will help to atomize or vaporize the excess raw gas to help it burn, and then the engine may stay running, but run very rich.
It's hard to tell looking at the picture, but it almost looks like the little welch plug is missing where the primer sends air into the carb bowl to pressurize it to force the fuel up through the main jet to enrichen it with fuel for starting. The plug might be there and rusted a bit, its hard to tell by looking at the picture, but you can blow them out by using compressed air in the primer bulb hose fitting on the carb body.
The float needle seat is a common replacement part, but you should have the special insertion/installation tool to put it in right and make sure you install it in the proper direction with the grooved face of it facing into the hole, otherwise you installed it backwards.
The installation tool only installs it so far, and not too far. The tool has a hook on the other end to remove the seat. The tool was available from Tecumseh years ago.
You removed the needle seat the easy way by blowing compressed air into the fuel inlet of the carburetor, and good luck finding it somewhere on your garage floor, that does happen.
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post #7 of 14 Old 11-18-2019, 05:54 PM
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Quote:
Originally Posted by ST1100A View Post
you should have the special insertion/installation tool to put it in right

I have used a 5/32" pin punch or the shank of 5/32" drill bit with great success, since I don't have the Tecumseh seat tool. A little oil on the edge of the seat will help it go in easier.


It looks like you have a blue plastic emulsion tube, so putting new O-rings on it would be a good idea also. You can use a flat blade screw driver through the carb throat to push down on the tube to ease removal.

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Toro 721-QZR (38743) 2015 (Hemi Predator Power)

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Last edited by Grunt; 11-18-2019 at 05:58 PM. Reason: Add info
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post #8 of 14 Old 11-18-2019, 06:40 PM Thread Starter
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Great info, thanks guys! ST1100A - great point on flooding the engine with too much gas. I will be that is the issue.

I did order the specialty tool today but will try Grunt's method with a small drill bit too.

Long shot of a question, but do you suspect the Briggs and Tecumseh needle seats are the same? I have a bunch of new Briggs needle seats and ordered some Tecumseh - but it will take 4-5 days to get here. They do look similar but I don't know about the exact fit.


You guys are great, thanks again!
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post #9 of 14 Old 11-18-2019, 06:47 PM
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The Tecumseh manuals also reference the use of a drill. The tool is more helpful for removal, but Inhave never had a smallnhook at the end of a paper clip fail me yet, and if you are not seating it fully (no matter what tool you use), you are doing it wrong. The side is critical, as noted, but the tool does not help with that. 40+ years doing it this way, never had one less than perfect . . .

Not sure the primer welch would affect start, since it does not seal the cavity it sits in - that one is more of a shield to keep fuel out of the primer hose, but is open to the carb bowl. Notnsure what I am seeing thier either, since every carb I have been in (no matter the age) has still had shiny welch plugs . . .

Considering the unknown condition, you ought to just spend the $12 or so on a kit - it will have the seat, o rings, fresh needles, and welch plugs . . .
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post #10 of 14 Old 11-19-2019, 01:30 AM
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A lot of the Tecumseh and Briggs seats are pretty much the same, especially if it is a Walbro carburetor.
Like Grunt mentioned, the drill bit will work.
The special tool has a tiny end on it that acts as a stopper to prevent you from installing the seat in too far, plus it has a tiny hook on the end of it like the hook on a crochet needle for seat removal.
A tip Tadawson used is a little hook made with a paperclip works.
Some times the special tool is hard to find, so if you can find one, get it, the tool does come in handy for many carburetor repairs, and make sure you don't loose the tool, it is a small brass tool shaped almost like a long drill bit. The tool is "Stepped" on the seat installation end with the tiny hook on the other end. You can usually find that tool on EBay. If I had the part number right here with me now, I would give it to you to make it easier to find and order.
A trick I use is to lightly grease the seat with silicon grease for ease of installation, do that and they go in real smooth. The little "Step" or tab on the end prevents you from installing the seat too far, which can be done if you force it in without lubricating it first for installation ease. The gasoline will rinse off the grease within a couple of minutes of running.
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