16.5 hp Briggs and Stratton I turn the ignition switch and flywheel only turns 1/4 of the way around and stops. If I keep turning the key eventually

[DollarBill]

Would be easier for us if you posted the complete engine number
However if it is an overhead vale engine then the symptoms are classic no decompression .
90% of the time this is because the valve lash on the inlet valve has gotten so big it is defeating the tiny movement caused by the ACR on the other 10% it is because the ACR mechinims on the cam shaft has self destructed .

I had a B&S single with exact symptoms mentioned. Adjusted valves for final resolution. Correct valve lash is paramount for compression release to function properly.

 

[eagle86801]

Your valves need to be adjusted.

Thank you the only trouble is is that every repair shop is backed up for three weeks . I'll try to make an appointment today . thanks again

Broken camshaft most likely. A very common issue with the B&S engines. Little nub that cracks open the intake valve breaks off and the starter can't pull the motor past the compression stroke. Easy fix if your mechanically inclined. A lot of people buy batteries, cables, solenoids and etc., but the issue is the cam not opening the valve most likely. I Also have seen where people just wind the motor backwards by hand to give to starter a running start. While that may work keep in mind the shrapnel from the broken cam is in that motor and can damage it.

thank you you help I'll look into this

 

[Gumshoew]

Sound Iike pressure relief mechanism on cam is defective.

 

[DinosaurMike]

Eagle86801, did the gas shutoff valve help? That was my solution on a Troy-Bilt tractor with a B&S engine some years ago. It lookd easier than pulling the carb. It works every time that I turn the valve off. One time I forgot and removed the spark plug to let out the gas by cranking the engine. Except I neglected to cover the spark plug wire and proved that it is a very smart idea to keep a fire extinguisher in the garage. Thankfully the only damage to the tractor was the headlight wiring. The damage to my ego was overwhelming. The engine runs fine.

 

[eagle86801]

Eagle86801, did the gas shutoff valve help? That was my solution on a Troy-Bilt tractor with a B&S engine some years ago. It lookd easier than pulling the carb. It works every time that I turn the valve off. One time I forgot and removed the spark plug to let out the gas by cranking the engine. Except I neglected to cover the spark plug wire and proved that it is a very smart idea to keep a fire extinguisher in the garage. Thankfully the only damage to the tractor was the headlight wiring. The damage to my ego was overwhelming. The engine runs fine.

I did install a fuel shut off valve and the few times I started it it started normally . Then I shut the valve off and ran the engine until it ran out of fuel and stopped . Dumb me the first time I forgot to turn the key off luckily it didn't kill the battery . This was the easiest fix I'm hoping the shut off solves the problem if not I move on the the other great suggestion I got on this forum . Thank you for your help.

 

[Robusta]

16.5 hp Briggs and Stratton I turn the ignition switch and flywheel only turns 1/4 of the way around and stops. If I keep turning the key eventually it will start and run strong . 2022 a new battery, solenoid ,ignition switch its started normally from Oct 2022 until May 15 2023 now its acting up again . I ordered a new coil .

Sounds like compression release. Remove your air filter, cover intake with your hand and crank it. After one hesitant revolution it should crank with speed and start.
If you cut off the air there is nothing to compress so it will spin.

 

[eagle86801]

Sounds like compression release. Remove your air filter, cover intake with your hand and crank it. After one hesitant revolution it should crank with speed and start.
If you cut off the air there is nothing to compress so it will spin.

thank you for your help

 

[Cajun power]

couple of ideas:

never assume new batteries are good. Try to bypass your battery. I use my truck battery and "jump/bypass" the mower battery (if you don't have a load tester). If the mower rolls over and starts...you have a bad battery or a low state of charge. solve that. recharge the mower battery with a charger and try again. If it starts and runs then that solves the low state of charge issue. it if continues to have problems starting then your battery is either bad or the charging circuit to it is bad measure voltage from charging circuit during run...should read at least high 13 volts up to 15 volts, with mid 14 volts usually being typical.. Or it can be some kind of parasitic drain on the battery during storage.

next...for engine related diagnosis...quick things to do to rule out engine problems.

take both spark plugs out. rotate by hand...should rotate easily with very little resistance...if you take the valve covers off when you do this, you can see the valves moving....notice the auto compression release cycle...both valves should pop just slightly...if they don't, either that ACR has locked up and failed OR the valve lash and timing is bad. Do the valve lash clearance ...do it per the service manual. be precise. Does flywheel magnet match up to corresponding ignition coil modules at top dead center? refer to service manual for this position. Sometimes woodruff/keyway get slammed and timing is off. it's an easy thing to check. It's rare, but sometimes they keyway on the flywheel shaft gets slammed and drifts.. By checking the position of the magnet to the coils you can see if there is some misalignment that has affected timing. Try rocking the flywheel back and forth. There should be zero play.

has anyone adjusted valve clearance recently? it's a common mistake to bork this up when doing valve clearance and timing adjustments. I've done it twice and though I consider myself pretty good at it. Pay attention to magnet to coil position AND when top dead center actually happens.....and noticing when auto compression release occurs in the cycle. to the untrained or careless eyeball, that subtle movement can be hard to notice. Be precise.

 

[Mattdad1]

I would try removing the air filter and cupping your hand over the carburetor air intake. Try to start the engine. if it starts, you have a broken compression release.

 

[eagle86801]

couple of ideas:

never assume new batteries are good. Try to bypass your battery. I use my truck battery and "jump/bypass" the mower battery (if you don't have a load tester). If the mower rolls over and starts...you have a bad battery or a low state of charge. solve that. recharge the mower battery with a charger and try again. If it starts and runs then that solves the low state of charge issue. it if continues to have problems starting then your battery is either bad or the charging circuit to it is bad measure voltage from charging circuit during run...should read at least high 13 volts up to 15 volts, with mid 14 volts usually being typical.. Or it can be some kind of parasitic drain on the battery during storage.

next...for engine related diagnosis...quick things to do to rule out engine problems.

take both spark plugs out. rotate by hand...should rotate easily with very little resistance...if you take the valve covers off when you do this, you can see the valves moving....notice the auto compression release cycle...both valves should pop just slightly...if they don't, either that ACR has locked up and failed OR the valve lash and timing is bad. Do the valve lash clearance ...do it per the service manual. be precise. Does flywheel magnet match up to corresponding ignition coil modules at top dead center? refer to service manual for this position. Sometimes woodruff/keyway get slammed and timing is off. it's an easy thing to check. It's rare, but sometimes they keyway on the flywheel shaft gets slammed and drifts.. By checking the position of the magnet to the coils you can see if there is some misalignment that has affected timing. Try rocking the flywheel back and forth. There should be zero play.

has anyone adjusted valve clearance recently? it's a common mistake to bork this up when doing valve clearance and timing adjustments. I've done it twice and though I consider myself pretty good at it. Pay attention to magnet to coil position AND when top dead center actually happens.....and noticing when auto compression release occurs in the cycle. to the untrained or careless eyeball, that subtle movement can be hard to notice. Be precif theses things