Tecumseh LV195SE lawn mower engine won't start.

[Oddjob]

Once you eliminate fuel, spark and timing, the only cause for nonstarting that I can think of is low or no compression.

 

[Dave T S]

Once you eliminate fuel, spark and timing, the only cause for nonstarting that I can think of is low or no compression.

That was my thought. 45 psi is half of what some state is the minimum for an engine like this. The range stated is 90 psi to 120 psi.

 

[Tiger Small Engine]

That was my thought. 45 psi is half of what some state is the minimum for an engine like this. The range stated is 90 psi to 120 psi.

If compression reading is accurate, then 45 psi is too low for engine to start and run. You need about 60-70 psi minimum for most 4-stroke engines to start and run. The problem is that there is often a compression release involved and it throws off reading. The compression tester may be off on accuracy. Is the 90-120 psi spec in general, or specifically for this engine? In general, 120 psi is what a healthy 4-stroke will read.

 

[Dave T S]

If compression reading is accurate, then 45 psi is too low for engine to start and run. You need about 60-70 psi minimum for most 4-stroke engines to start and run. The problem is that there is often a compression release involved and it throws off reading. The compression tester may be off on accuracy. Is the 90-120 psi spec in general, or specifically for this engine? In general, 120 psi is what a healthy 4-stroke will read.

Thank you. I'm taking head off, cleaning carbon from the valves and piston head. Looking for other problematic opportunities. Thanks for everyone's help here.

 

[slomo]

taking head off, cleaning carbon from the valves and piston head.

In every engine manual out there as a periodic maintenance item. Good job. Could cause low compression. Chunk of carbon holding a valve open. Valve seat out of the block from over heating. Compression release little too active, is that even a thing? Failing compression release. Poor valve sealing. Rings stuck to the piston. Gouged up cyl bore.

What happened to we needed a special compression gauge for small engines? Something about small cc's and the hose on the gauge?? Like we aren't supposed to use a typical car/truck engine compression tester on a small engine? Or a tester with no hose was better??

 

[StarTech]

You traitor....Giving a way trade secrets is just not right.

You know they are to use an automotive gauge with 10' hose.

 

[slomo]

Oh that one with the 3/4" ID hose. Thanks for jogging the memory LOL.

 

[reubj]

Well this thread degenerated quickly.....

 

[Dave T S]

Well this thread degenerated quickly.....

 

[Dave T S]

How can I tell if the rings are bad and the bore is gorged beyond repair? Thanks for all your help and all the fun side comments......