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This is a NEW post in reference to same engine as previous post labelled "TECUMSEH L-Head Definitive valve Clearances"


History;
Snow blower is an MTD 28 inch about 10-12 years old and belongs to an elderly neighbor I help out.
Engine is 10HP Tec LH358SA ran well at end of last winter according to neighbor.
Transmission was frozen this fall when he was getting ready for winter so he asked me to look at it.
I replaced a corroded gear and freed up the transmission so it rolled freely forward and backward without the engine running to move it around in the garage. Previously it would not even budge an inch.
When I tried to start it before returning it to the neighbor it was very difficult to pull the recoil so I used the electric starter.
The electric starter ran for 2 burst and then the engine was ceased!
I had to remove the electric starter and then I could turn the engine over by using a big socket and ratchet on the shaft end where pulley is but it was definitely not smooth. it would bind and then smooth out till it got around again to whatever was creating the resistance.


I have been tinkering with Tecumseh engines for over 20 years. the extent of my tinkering is removing and cleaning carbs; removing and replacing contact points/condensers. removing replacing electronic ignition modules with lots of success.


I have never been inside one of these engines so I decided this was going to be the first!. I suspected the connecting rod was broke but that was not the case.


That said this is what I did:


Removed engine from frame of snow blower.
Removed Shroud, flywheel, Sump cover, oil, and head.
Removed crankshaft, camshaft and lifters, and even the piston from the block. (labelled lifters so went back same way.
DID NOT REMOVE VALVES AT THIS TIME.
Cylinder was spotless no signs of wearing at all.
Inside the engine was spotless as well. No sludge. No metal shavings. Very clean oil. everything was shiny. inside.


I took the crankshaft and cam shaft to our local Ariens dealer that has a tremendous reputation to inspect the compression release mechanism on the cam shaft and they said it all looked good and had no advice for what could have caused the binding in the first place...…..


So I decided to put it all back together.
Had to buy a compression ring tool as I struggled to get the piston back in the cylinder without it.
I even bought a new torque wrench that I never owned before.
I put it all back together and no binding??
Yes I watched a you tube and made sure the crank and cam markings were aligned perfectly.
Before I put the head on I was able to rotate the flywheel by hand with no binding at all. The valves went up an down and all looked good to me.
I put all the externals parts back on...……..shroud, sump cover, ignition module, carb (after a thorough cleaning even though it looked clean inside), fuel tank (cleaned it earlier), replaced fuel line, purchased a new muffler as original was all disintegrated on surface that attaches to engine.
I installed and torqued the head per the published specs...………………


I was now ready to try and start it up. NOTHING absolutely NOTHING but a dry plug, plenty of spark, but WOULD NOT START.


I was directed to look at the valve clearance from reading stuff in the forum so I removed the head again put the cylinder at top with both valves closed and took the measurements of Intake at .005 and exhaust at .007 as I recall. That's when I wrote the post "Tecumseh L-Head definitive valve clearances.


I know this is long winded but guys in the forum like facts and steps so I am trying to recall as many as possible.


I filed both valves to be .011 and put it all back together last night.


Tried to start it this morning and still have nothing! plenty of spark, no wet plug so I am leaning towards a lack of compression and don't know why??


I know fuel is flowing to carb. I know carb is passing fuel into chamber when I push primer button. Can see it and smell it.


I do not feel a tremendous amount of resistance on recoil when I pull it. there is some but nothing like my own Ariens with same 10hp Tecumseh.


I have tried everything within my knowledge of these TEC engines and am seeking now seeking additional help.


Can compression be measured on engines with a Compression release mechanism? Somewhere I think I read you need at least 70-80 Pounds of pressure to get the BANG.


Frustrated as all get out.
 

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Yes you can test but need the electric starter to do the compression test, has a similar issue with a 4 stroke single stage, took most of engine apart mostly just to learn as I only spent $50 on it so no big loss if I killed it, but got everything cleaned and tightened up and it also seemed to be low on compression, Then I remembered someone telling me to put a bit of oil on the cylinder wall of a freshly assembled engine so I put some marvel mystery oil in the plug hole and it seemed to draw fuel a little better and finally started, don’t know if the oil helped or just got lucky but it seemed to work out and now I have a running single stage to use.
 

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will it at least try to run if you spritz it with a bit of starting fluid? That will at least let you know you have timing and spark set up correct. If so, then it might be as simple as a gas flow problem.... check needle/seat and float levels..... if you can keep it running with ether then you know something is amiss on the carb side.
 

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Hello All timing marks on cam and crank correct. Piston rings staggered when replacing piston. Piston/rod replaced in cylinder correct ? If you did all that you should have lapped the valves. Prior to that a leak down test to see leakage bypass valves. You can perform a leak down test now that engine is assembled. Maybe valves should be set lash at .008. Check Spark. Check flywheel key position and set coil lash at .010 gap. If spark plug is dry then move to carb cleaning and adjustment. Check linkage positions on carb then adjust govenor.
 

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Do a leakdown test on it to see where it may be leaking compression. If you did not have the valves out, a valve might not be sealing. A bad valve? A bad or loose seat? Pitted valve faces or seats? A stuck valve in its guide? Possibilities.
At least you got the experience of tearing an engine down to see what is inside of it. The more you do, the better you will get with them.
If it has a leak in the valves you would hear air hissing out of the exhaust or the carb, if it is a cylinder leak, rings, you would hear air leaking out of the oil fill or the engine breather tube.
Just a couple of hints to experiment with if it appears to be lacking compression.
Normally to check leakdown, set the piston approximately 1/4 inch past top dead center on the compression stroke so that the valves are fully closed in case it would have an automatic decompression release.
 

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When you assembled engine, did piston rings roll freely in their groove ? When an engine seizes, the ring sticks in the ring groove . Best bet, remove rings, clean piston grooves up, a small file works great, give bore a quick honing so oil can stick to cylinder, test fit piston in bore, should slide smoothly top to bottom . Put one old ring in bore, use piston to square it up, measure end gap of old ring. Now use a new ring, and again measure gap . If gap is too small, one end of ring must be filed, until gap is same as old ring . Put new rings on piston, oil rings, and verify they rotate . Now you have an engine that won't seize when it heats up . When you added mystery oil, it loosened the stuck ring, or helped seal piston. Hope that helps . Nothing is worse than fixing an engine, only to have it fail worse later .
 

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Discussion Starter #7
I just got back to looking at this engine. Had some personal issues going on.
I can get it to start if I push the primer button 10-15 times. It fires but only runs for a few seconds.
Sounds like a fuel deprivation problem.
The carb has been off several times and is absolutely spotless. The float is set right jets are clean bowl is clean. New float, seat and fuel inlet valve
Has fixed main jet so no adjustment needed.
All I can think of is the intake stroke isn’t sucking fuel into combustion chamber.
This engine is driving me nuts.

Any more ideas out there before I throw in the towel on this engine.
 

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You may want to check theengine's compression. Sounds like low compression, which will not be enough to allow the intake to suck in additional fuel needed after the primer bulb injects some.
 

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Discussion Starter #10
That’s exactly where I was going. No idea why I would have low compression. This engine ran great a year ago.
 

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Discussion Starter #11
If I didn’t align the cam and crank shafts correctly (which I don’t think I could have messed up)........could this cause the engine to not suck fuel in?
 

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You didn't mention checking the fuel line for cracks and/or filter for blockage; it sure does sound like a fuel starvation issue. Good luck.
 

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Discussion Starter #13
Should have mentioned I Put a new fuel line on when I had cowling off. I am close to giving up on this engine. Never been more frustrated with a tecumseh. I love these engines but this one has got me stumped. Wish I could measure compression but the compression release doesn’t allow for good readings right?
 

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if it has electric start, that will give you a good compression test, But the pull string is impossible to get a good reading as your stating.
 

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You could have a leaking valve causing loss of compression.
A valve could be sticking in its guide, a bad valve face or seat. Pitting or cracks, or just worn.
You could dress up the seat and faces by using some lapping compound, or if you have a valve seat cutter and a valve grinding tool. Most of the time if it is a bad valve, you usually just replace the valve unless it isn't too bad and you have the skill and tools to do a valve job like that.
I would give it a "leak down" test first, to determine if it is a leaking valve or something else, like a head gasket or rings, cylinder leakage before you remove the cylinder head.
 

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Having the same issue

Bobami;

This is exactly the issue I'm having with a Tecumseh LH318SA engine now, that is mounted on an Ariens 932105 blower. When I got it, I had spark, yet could not get it to fire or sputter at all. Took off the carb, and discovered that there was no throttle plate in the carb! Made me wonder where it went.....Put on a new carb.

Took off the head, and found the throttle plate screw embedded in the head. Did not find the throttle plate. Adjusted the valves and put it back together.

Like you, I have fuel in the carb, yet my plug is dry, without even an odor of gas. I need to pull the feeder conduit that connects the carb to the engine, and make sure the throttle plate is not stuck in there (I should have done that before).

I'm wondering whether I have such poor compression that I don't get any suction of gas? And, since I've got spark, I assume that the key is not sheared (but that's an easy check).

Checked and the key was not sheared. I have good spark, yet even with fuel in the plug hole, don't even get a sputter. I'll head to Autozone tomorrow and get a compression gauge to see what's up. Still don't know what happened to the original carb throttle butterfly! It's nowhere to be found.
 

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Are both valves operating properly? If the throttle plate screw made its way into the head, it might have damaged the intake valve seat on the way through. So even if both valves are moving, they might not be sealing correctly. Does the cord feel too-easy to pull?

To run, you need fuel, compression, and spark (at the right time). You gave it fuel. And you checked both spark, and the flywheel key (important, since you'd still see a spark if the key was sheared, it would just be at the wrong time). So compression is next on the list.

Does the engine pull air into the carb's intake when spinning? And blow air out the exhaust? This is easier to check if it has electric start. It's a crude way to help ensure that, for instance, you don't have one valve that's never opening, which would prevent actual airflow through the engine.
 

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I've seen that happen a couple times. The screw puts a little nick in the valve face and the seat causing a valve leak, low compression. A leak down test would have found the leak right away.
If it isn't too bad, you can regrind the valve a little bit and re cut the valve seat and it should seal itself to bring your compression back so it will start and run again.
 

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Thank you RedOctobyr and ST1100A;

I stopped by Autozone this evening and borrowed a compression tester. Checked it on my own blower to make sure it was working, then hooked it up to the engine in question. Cranking with the electric starter, I got no reading at all, meaning the gauge needle did not move at all. I then put my hand by the muffler and felt strong outward airflow. When holding my hand by the carb choke, I had no suction.

So I'm guessing I have an intake valve issue. Time to pull the head again and pull the intake valve and either replace it or lapp the valves. Might as well lapp both since I'm in there. I also remember seeing the intake valve collar (can't remember the name, but what the valve stem passes through towards the head) looking like it was rising up towards the head. I assume that should be re-seated downward?
 

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I think that's the valve guide. I don't know if they can just be pressed down again, or if something more in-depth is required. I've heard discussions about that, but you'd have to look into it further.
 
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