No Spark No Compression but Recoil Starter turns Blade 4hp B&S.

[cprodave]

On a Murray 22inch Mower 4hp Briggs & Stratton Sprint Model 10J902 Type 0293 Code 05042651 will not start. Using an adjustable gap Spark Tester I see no Spark. Using Compression Tester I see zero compression. When I pull the Recoil Starter Rope the blade DOES rotate correctly (indicating that the Starter is properly engaging/turning the Crankshaft. After I attempted to start I removed the Spark Plug and did not detect any fuel, indicating there is no vacuum drawing fuel into the cylinder. I sprayed Starting Fluid into the cylinder, replaced the Spark Plug and got no "cough" or signs of ignition.

I'm not a pro but not a newbie either working on small engines and outboards but it is puzzling to me that both Spark and Compression have failed at/around the same time. I don't have exact info on how the mower was being used by distant relative at the time that it stopped working. I know how to debug for No Spark (Coil/Flywheel gap check, check Resistances, Flywheel key broken etc) , and how to diagnose No Compression (stuck valve, broken rod, broken ring, etc) , but what would cause them to both fail at the same time?

Before I dive-in on disassembly and diagnosis, does anyone have tips on what else to look for? Thanks in advance for any ideas. Dave

 

[Rivets]

You have a 15 year old engine, on a $1.98 mower. I’m will to bet you have a sticking valve and possibly a mouse nest under the shroud. This nest would cause your engine to over heat, which could easily be the cause of your problem. Ask yourself, How much $$$ do I want to spend. If you remove the shroud, you might Get some idea as to what happened.

 

[Scrubcadet10]

stick a screwdriver into the plug hole and spin the engine see if the piston is moving. or place your finger over the plug hole while you spin it and see if any air moves.

 

[cprodave]

I found an easy fix on the Spark problem already. There was some dried grass mixed with oil in between the flywheel and coil. I cleaned and reset the gap, it has a strong spark now. I checked for piston movement--looks good. Pretty sure it is stuck valve. If parts to fix cost more than $40 i will probably get rid of this mower. Yes it is 15 years old. But it has seen little use because it is at a vacation cottage, mowing a very small area 2 times every summer. Thank all for input!

 

[cprodave]

The Intake Valve (top valve in photo) is stuck. The Exhaust Valve ( bottom valve in photo) moves freely. Without doing further disassembly what is the best way to unstick the Intake Valve? Rotate the valve by gripping with cloth covered Pliers or visegrip? Tap the valve inward with light hammer? Is prognosis bad for gear (or whatever drives this valve) to be broken? Thanks...

 

[cprodave]

Having trouble unloading photo...too large.

 

[Scrubcadet10]

Upload your photos to a image host (I use postimages.org) then place the link they give you here.

 

[Rivets]

More than likely you have a bent valve stem. This would mean replacing the valve, cutting the valve seat, grinding the valve stem to set clearance, lapping the valve and then assembling everything with a new head gasket.

 

[cprodave]

I got lucky. I tilted the mower back and shot carb cleaner plus some 30 weight along the stem. Waited a couple hours. Grabbed the valve with a rag and pliers, rotated it about 10 turns--stiff at first then it became looser. Untilted mower, pulled rope, it puked oil and carb cleaner out. Reassembled and it started up. Runs good now. Needs new spark plug (nearly fouled) and probably decarbonized--is SeaFoam best for this? Thanks all.

 

[cprodave]

Weird that this mower developed 2 unrelated problems simultaneously , right?