Mower wont start

[maradcliff]

I bought a mower at an auction which was partially disassembled, but all the parts were included minus a couple bolts. The flywheel and magneto were off, the engine head was off, as well as all the covers and the gas tank. I put it all back together. This is an electric start push mower and has all the bells and whistles. I put the head back on the engine as well as the flywheel, and magneto. I connected the gas tank even though it's sitting off to the side now (it covers most of the engine).

I connected a battery and turned the engine over. It spins nicely but will not start. With the spark plug wire off the plug, I see a very nice spark to the engine block, so I know it's getting a spark. I also know it's getting gas, but in fact, too much gas because the spark plug is getting soaked, and after cranking it with the battery/starter for awhile the engine would get very tight because of gasoline flooding. Pulling the spark plug made it turn easily again, but the plug was soaked.

I put a vice grips on the gas hose to stop the gas from flooding the engine. I still do not get even the slightest pop from the engine.

I put the spark plug on the end of the plug wire and can see a strong spark on the plug tip.

There is still some gas in the carburetor, and I know the spark is good. Why wont it start?

I have no idea why they had the head off, and the piston moves up and down properly, so do the valves, and the cylinder is smooth. I cleaned all the carbon off the head before I installed it. I can hear the compression, and since the gas flooding caused the engine to cease up, it's obvious there is compression. I dont have a compression tester but I can hear the compression.

Since there is a good spark, some gas, and compression, what the heck could cause it to not get at least a little pop? What else can I check? I have worked on many mowers in the years and never had one that wont at least make an attempt to pop.

This is a 4 cycle engine.

A few notes. I put in NEW gas. The oil is at proper level This has a bulb for cold starting I did NOT buy a new head gasket, but it was in good shape, and like I said, it has compression. I am trying to start it using an external battery charger, so it is spinning fast enough.

Any ideas? I have run out of things to try?????

The only thing I can think is that there is just too much gas still remaining in the cylinder, but I did turn it over quite a bit with the plug removed.

Mark

[Jordan]

Had the magneto flywheel off yet? Could be it's sheared the key and moved around to a different position. You'd get sparks, but at the wrong time.

[maradcliff]

I just came in from the garage and you are correct. The key was sheared and pretty much gone. It seemed to be made of aluminum or some other soft metal. Not having the right part, I made my own by hammering a nail square and cutting off the head. The mower started almost instantly.

Thanks for your help.

I probably should get the proper key, but at least i know it runs now, and runs quite well too. I did discover an oil leak where the lower part of the engine (pan) is bolted to the upper part, so i suppose I should replace that gasket too, or at least get some silicone in there.

One question is where to find any technical data on this engine. It's a Tecumseh model VLV126. The Tecumseh website does not even list this model, and their site is bloated with flash crap, so it takes forever to load. In the end it's useless. I am looking for two things. #1. Exploded view of the engine. #2. Adjustment information so I can adjust the carburetor and govenor (the speed is slow). If anyone knows of a site that has this, please let me know.

Just curious. Why would they use such a soft metal for that key? I guess it's intended to shear if the flywheel jams up, but I cant see why the flywheel would jam. If anything will jam, it will be the blade, but not the flywheel.

Mark

[NickySantoro]

Sounds like the carb is gummed up. I'd empty the gas from the tank and carb then put a few ounces of carb cleaner into the tank and crank it over. Then I'd let it sit over night then add some fresh gas and try again. FWIW YMMV

[Pop]

...

If the blade hits an immovable object, the shear pin will go rather than the crank and many other parts, plus it'd probably bend the shaft in the process. You really should get the right pin back in it. Same as the shear pin on an outboard motor if you're familiar with that.

Pop

[maradcliff]

Thanks for the reply.

If the shear pin was on the blade or blade mounting attachment I'd agree with you. But this shear pin is on the flywheel, (located on the top of the engine). Unless someone was to intentionally stick an object thru the plastic cover over the flywheel, there is no reason the flywheel will jam up. I do intend to get the correct part since I need other parts anyhow, but I just can not understand why they have a soft metal pin up there......

If anyone knows of a website that has an exploded view and parts list, or tuneup instructions for Tecumseh engines, please post the website. I cant seem to find any. Briggs has all of them, but Tecumseh has a website that's pretty much useless.

Mark

[John Lawrence]

The fly wheel key serves a duel purpose. (1) It insures that the engine will remain on the correct timing position.(main purpose) (2) The weighted fly wheel is spinning at a high rate of speed. Should the mower hit a permanent object and not have the ability to shear off a 50 cent key, the flywheel, having the tendency to keep moving, will probably cause serious damage, such as a broken or bent crank. (secondary purpose)

Even with a key in place, if it is not the proper one, damage can and does occur. I used to have a repair shop in my younger days and replacing flywheel keys was a large part of our summer business. Very rarely did we see the key on the blade end of the crank shear off.

[maradcliff]

I guess that makes sense. It bet this shear key was the reason the former owner dumped this mower at the auction, in pieces. He took off the flywheel and never noticed the key was sheared off. He then took off the engine head and gave up on it. I think I got myself a deal since I bought the mower for $4, and I can tell it was an expensive mower since it has everything. It is self powered, and has lots of other features plus a 6HP engine. The grass catcher bag is missing but I never use them anyhow.

Mark

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[Goedjn]

Well, you're looking at it because it sheared, right? Which means that either the flywheel stopped when the shaft didn't, or the other way around. DOesn't much matter which.