Tecumseh LH358SA Will not Start- Need Help - Snowblower Forum : Snow Blower Forums
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post #1 of 38 Old 03-11-2019, 12:05 PM Thread Starter
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Tecumseh LH358SA Will not Start- Need Help

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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post #2 of 38 Old 03-11-2019, 12:36 PM
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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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post #3 of 38 Old 03-11-2019, 04:41 PM
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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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post #4 of 38 Old 03-17-2019, 07:24 PM
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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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post #5 of 38 Old 03-18-2019, 01:02 AM
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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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post #6 of 38 Old 03-18-2019, 05:37 PM
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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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post #7 of 38 Old 05-11-2019, 07:15 PM Thread Starter
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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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post #8 of 38 Old 05-12-2019, 12:34 AM
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Air leak in intake? Maybe a munged gasket on reassembly?
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post #9 of 38 Old 05-12-2019, 07:04 AM
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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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post #10 of 38 Old 05-13-2019, 04:34 PM Thread Starter
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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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