Tecumseh Start Problem

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  #1  
Old 05-16-11, 07:20 PM
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Tecumseh Start Problem

Tecumseh LV195EA engine on a Toro mower. Ran fine at the beginning of the season. Then I had trouble starting it--would need to repeatedly pump the primer bulb and pull the start cord. It would fire briefly and then die. A few more attempts and it would catch and run. Then it would only pop a few times and die. It also made some unpleasant clanking noises. Now it won't pop at all.

Turns out the blade bolt was loose which probably accounted for the clanking. I figured this was the problem but it was not.

Here's what I've checked.

1) Compression. Seems fine. I didn't check it with a compression gauge but it seems pretty much like it always has when I pull the starter cord.

2) Timing. I visualed the flywheel key. It's there and doesn't seem damaged at all.

3) Spark. I took out the spark plug, wired it to the engine casting and pulled the starter cord. I get a blue spark. I didn't try seeing how long a spark I could get.

4) Fuel. Fresh fuel. Pumped the primer bulb, pulled the starter several times, removed the plug, and smelled the spark plug hole--no gas smell. Clamped the supply hose shut. Removed the carb bowl. Opened the clamp on the supply hose. I get plenty of fuel when the float is low. No fuel when I raise the float. Float has no fuel inside (plastic float). Pulled the main jet. Used a small copper wire and all orifices are open. I'm soaking it in carb cleaner just in case.

While I was mucking around I changed the air intake filter. I removed it later and noticed there were some oil droplets splattered on the inside of the air filter. I'm not sure were they came from and if they're related to my problem.

For what it's worth, it seems like the primer bulb has become easier to pump during this period of time. It could be me, but it just seems like it's not doing anything. I hunted around for some spray starter fluid but I guess I chucked it out. I was going to spray some into the intake and try starting the engine.

What should I check next? I'm not familiar with primer carburetors. When I pump the primer where should I see fuel? If the float valve works and the main jet isn't clogged why am I not getting fuel?
 
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  #2  
Old 05-16-11, 09:53 PM
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It is most likely that the flywheel key is sheared this almost always happens with a loose blade the pounding of the blade shears the key you should pull the flywheel. The outer screw of the air filter mount must be in place for the primer to work. Fuel should be pushed out of the emulsion tube in the center of the carb when you push the primer. To properly prime a Tecumseh engine you must push straight in and hold it in and then wait a second between primes.

AJ
 
  #3  
Old 05-17-11, 06:13 AM
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I pulled the starter cup and can look down on the flywheel keyway and the key. They're in perfect alignment. The key is not smashed or offset in any way. Besides, that wouldn't explain why I don't smell any gas by the spark plug hole after priming the engine and pulling the start cord many times.

Thanks for the tip about the outer screw of the air filter mount. I never would have figured that out. I let the main jet soak overnight. I'll put it back in, put the outer screw in place, and see if the primer works. I found an exploded view of the carb. It looks like you create air pressure with the rubber bulb and then open a valve to inject some fuel. Is that why you're supposed to wait one second--to give that small volume of air time to push out the fuel?
 
  #4  
Old 05-17-11, 08:19 AM
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You cannot check the key by just looking at it, you must remove the flywheel, please check the following pictures of a Tecumseh key that looked good from the top, however check the second picture. Have a good one. Geo
Looks good here.

However,
 
  #5  
Old 05-17-11, 08:32 AM
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The reason for waiting between primes is to let the fuel refill the chamber in the center of the carb. If you do three quick primes you only get one prime. If the bowl gasket does not seal the carb wont prime. When you push the primer you are pressurizing the bowl which forces the fuel up the emulsion tube there is no valve. I'm not saying that the key is sheared but 9 times out of ten if the engine is run with a loose blade it will be.

AJ

Great picture Geo!
 
  #6  
Old 05-17-11, 01:44 PM
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More Info

OK, so here's some additional information. I reattached the carb bowl after soaking the main jet in some cleaner. I pumped the primer (and waited briefly between pumps) and pulled the starter cord a number of times. No pops, no combustion of any kind. Then I took some aerosol brake cleaner (the only flammable aereosol I could find) and sprayed it into the air intake, air filter removed of course. I pulled the starter once and it fired up and ran fine. This engine is set to run at high speed all the time so I don't know anything about its idle performance. This indicates the compression, timing, spark, and high speed fuel circuits are fine.

I rolled up some paper towelling, inserted it into the bore of the carb, and rested it on the emulsion tube. I pumped the primer bulb 10 times. The towel had no gas on it. So I figured the primer must be bad. I looked carefully at the bulb and it looks just fine. I removed the retaining ring, the bulb, the plastic thingy with the small O-ring and the spring. The bulb doesn't leak and is springy, not brittle. Also, I poked a wire up the emulsion tube and it's clear. In fact, the inside of the carburetor looks quite clean. The fuel bowl sits flat and the O-ring for it looks fine. All the passages I can see in the area where the primer mounts are clear.

So, what's next guys? For what it's worth, this looks to be a series 11 Tecumseh carburetor.
 
  #7  
Old 05-17-11, 02:14 PM
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Did you remember to put the outer screw back in? Also you need to press and HOLD the primer in to get a full prime. If still no prime the bowl gasket must be leaking. It is quite easy to look into the carb while you prime.

AJ
 
  #8  
Old 05-17-11, 04:15 PM
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That carb is difficult to prime if the bowl gasket is leaking as it doesn't create enough pressure to force the fuel up the nozzle, also the bowl nut must be very clean, the tiny hole near the edge of the threads at the top of the bowl nut(almost invisible) is usually the problem, I clean it with the wire from a twist tie. Have a good one. Geo
 
  #9  
Old 05-17-11, 04:52 PM
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I remounted the plastic air cleaner base so both screws are back in place. And I did hold in the bulb during the priming operation. The small passageway in the bowl nut you mention is perfectly clean, and was that way before I soaked the bowl nut. The other two passageways in the bowl nut are clean as well (all verified by running a fine copper wire through them).

So that leaves the bowl gasket. As I mentioned, it looks fine--no nicks, cuts, deformed areas, etc. Is there some way I can test it before I go replacing it? Can I pressurize the bowl somehow and put some soap/water solution around the perimeter of the bowl? If it is the gasket I don't understand how it could have failed so quickly. 'Tis a puzzle.
 
  #10  
Old 05-18-11, 12:27 PM
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Ding! Ding! Ding!

We have a winner. Two of them actually (AJ and Geo). It was the bowl gasket. Since we had eliminated most of the other candidates I pulled the bowl again and rechecked the gasket. I flexed the gasket this time and there were many cracks visible. Also, the inside rim of the bowl was corroded which I'm sure didn't help the seal. I cleaned up the bowl rim with fine sandpaper and emery paper and installed the new gasket. Three pumps, one pull and we're off to the races.

I checked the engine date code--it's less than 5 years old. I'm really surprised the gasket was so cracked. I don't know if it's the ethanol blended fuel but it seems like that gasket should last longer than that.

Anyway, thanks for the help!
 
  #11  
Old 05-18-11, 03:58 PM
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Success is a wonderful sound. Have a good one. Geo
 
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