LA115 starting problem

[kmills74]

The engine cranks but will not start. Fuel feed is okay and spark plug sparks. Will not start with starting fluid, either. Running fine yesterday. I got too close to the lake edge while mowing and had to physically pull the mower away from the edge. Turned mower off, released the transmission, and pulled the mower backwards about three feet. Started it back up and realized I'd forgotten to push the release pin back in when I stepped on the foot pedal and no go. Turned mower off, pushed the pin in, and cranked - no start. Smelled like it was flooded so I let it sit for 30 minutes. Still no start. Since then I've changed the spark plug after first testing the fuel pump, carburetor, and spark. Could it be out of time? I haven't pulled the fan yet to see if I've sheared the flywheel-crankshaft woodruff key but the flywheel spins like it always has. What I've read seems to indicate that it would be erratic if the key was broken.

The engine is a B&S 19.5HP OHV. Anyone have any suggestions?

 

[Auto Doc's]

Hello kmills74,

Quit shot gunning parts without understanding what you are doing. It just creates confusion and often more problems than it ever began with.

Fuel, Air, Compression and Spark are the basic needs for these engines to run.

The last possibility on a rider would be a sheared flywheel key. That would be an issue with a push mower if you hit something hard to make the engine suddenly stop. Exception: If the flywheel has been off recently and was not retightened correctly when installed.

This is a 19.5 B&S single cylinder, so the most likely issue is the valves have not been adjusted. With all the earlier events, the engine could have popped an intake rocker pushrod out of place and created the no start condition.

Sounds far-fetched, but I've seen it happen more than once when the valves have not been kept adjusted at least once every couple of seasons. (Or never adjusted at all)

A quick test for compression would be to pull the spark plug and stick your thumb firmly over the hole. Make sure the plug wire is out of the way to avoid a shock from the coil. Then have someone crank the motor briefly. If the valves are working properly, your thumb will be forced from the hole with considerable pressure.

If there is only slight pressure felt, the intake valve has likely popped off and no compression is being produced.

This would mean to sit down and watch a couple of You Tube videos about adjusting valves on one of these B&S single cylinder engines BEFORE you remove the valve cover.

Let us know what you find.

 

[kmills74]

Hello kmills74,

Quit shot gunning parts without understanding what you are doing. It just creates confusion and often more problems than it ever began with.

Fuel, Air, Compression and Spark are the basic needs for these engines to run.

The last possibility on a rider would be a sheared flywheel key. That would be an issue with a push mower if you hit something hard to make the engine suddenly stop. Exception: If the flywheel has been off recently and was not retightened correctly when installed.

This is a 19.5 B&S single cylinder, so the most likely issue is the valves have not been adjusted. With all the earlier events, the engine could have popped an intake rocker pushrod out of place and created the no start condition.

Sounds far-fetched, but I've seen it happen more than once when the valves have not been kept adjusted at least once every couple of seasons. (Or never adjusted at all)

A quick test for compression would be to pull the spark plug and stick your thumb firmly over the hole. Make sure the plug wire is out of the way to avoid a shock from the coil. Then have someone crank the motor briefly. If the valves are working properly, your thumb will be forced from the hole with considerable pressure.

If there is only slight pressure felt, the intake valve has likely popped off and no compression is being produced.

This would mean to sit down and watch a couple of You Tube videos about adjusting valves on one of these B&S single cylinder engines BEFORE you remove the valve cover.

Let us know what you find.

Thank you. I'm not certain a new spark plug counts as "shot gunning" parts but I really appreciate your comments. Whatever occurred happened from one moment to the next. One moment everything was hunky dory. The next, not. I'll check the compression with my thumb over the spark plug hole but when I cranked it without the spark plug in place it blew a good blast of fuel out. Is there a compression value it should read with a gauge screwed into the spark plug hole? The engine has about 340 hours on it so I'd already been planning a valve adjustment. For the record, I recently rebuilt the heads on my Subaru Forester and installed new gaskets so I'm not too daunted by the possibility of working on a mower engine.

 

[sgkent]

engines do not run one minute then die the next unless something changes. Did the engine get wet in the lake?

 

[kmills74]

engines do not run one minute then die the next unless something changes. Did the engine get wet in the lake?

No. Just close enough to the edge that I had to physically pull it back.

Here's the sequence of events: I turned off the mower, put on the brake, and got off. I pulled the tranny release pin but failed to release the brake. I grabbed the mower by the rear and pulled it backward and away from the lake's edge. I got back on the mower and realized I'd left the brake on which explained why it was a little difficult to pull. I started the mower and stepped down on the forward movement pedal. Of course it didn't go anywhere because I'd forgotten to push the tranny release pin back in. I turned off the mower, which backfired. Got off, pushed the pin back in, got back on and cranked. Flywheel spun but no ignition. Smelled gas so I figured I'd flooded the engine.

I've listed everything I checked in my initial post. My idea about maybe having sheared the woodruff key was simply grasping at straws. On a car engine, this no-start would likely be a timing issue. But Auto Doc's reply and my research tells me that's highly unlikely unless I'd been mowing and hit a big rock. So now I'm preparing to drain the oil and remove the valve cover. Best case is it's a simple valve adjustment issue. Worst case is I'll have a mower with correct valve clearances that still doesn't start.

 

[sgkent]

I'd do a compression test to see if you are getting normal compression.