Briggs 15.5hp engine - locks on compression

dsybert · 06-16-2009, 01:33 PM

I have a White lawn tractor with a 15.5hp OHV engine on it. I am having an issue where the starter cannot turn the engine over past the compression stroke. With the spark plug out, the engine turns over freely, and the valves are moving as they should. If you turn the engine over without the plug, its fine until you plug the hole, and then the starter tries to turn it over, but can't. I have replaced the starter, but no luck. Same issue.
Last year, this tractor ran fine, and all it has done since then is sit in my basement. This year, this problem arose.

Any help? thanks!

Zed101 · 06-16-2009, 01:40 PM

Just as a routine check, try putting a little oil in the sparkplut hole, turn the enging over a few times. Recheck the plug for depth! It may be the wrong type and goes in too far allowing the piston to hit and not complete its cycle.
Just for a test, if you have a shorter plug, wheather it is the correct one or not, try it. If it allows the engine to turn over , Thats the problem!
The oil may help the system anyway.

Good luck,

dsybert · 06-16-2009, 01:46 PM

Thanks. The plug clearance is okay. You can stop the engine from turning over by simply putting your finger over the hole. The plug is dirty and gassed, but the gap is still intact. thanks,

usnavyvet · 06-16-2009, 02:20 PM

battery ok? I'd check the voltage across the starter when cranking or try a new battery. It could be either a starter or solenoid issue as well. but even if a valve or timing issue, the battery should be able to push the engine through the compression stroke.

k2skier · 06-16-2009, 03:18 PM

Check valve clearance, about .004-.005, the compression release will not function with excessive valve clearance.

dsybert · 06-16-2009, 07:27 PM

I tried it with the battery, jumping the battery with a boost pack, and powering it right through the starter, to eliminate the key and everything downline. Still no luck. I will check the valve clearance, but the tractor ran fine last year. The valves shouldn't gain excessive clearance by just sitting for a year. Thanks for the replies. Anyone have any other ideas?

k2skier · 06-16-2009, 10:17 PM

Quote:

Originally Posted by dsybert

I tried it with the battery, jumping the battery with a boost pack, and powering it right through the starter, to eliminate the key and everything downline. Still no luck. I will check the valve clearance, but the tractor ran fine last year. The valves shouldn't gain excessive clearance by just sitting for a year. Thanks for the replies. Anyone have any other ideas?

If it's not the battery, (when you jump it, go straight to the starter), or valve clearance, it's a bad starter or bad cam shaft (comp release is built into cam).

06-16-2009, 01:33 PM	#1 (permalink)
dsybert Registered User Join Date: Jun 2009 Posts: 4 OS: win2000	Briggs 15.5hp engine - locks on compression I have a White lawn tractor with a 15.5hp OHV engine on it. I am having an issue where the starter cannot turn the engine over past the compression stroke. With the spark plug out, the engine turns over freely, and the valves are moving as they should. If you turn the engine over without the plug, its fine until you plug the hole, and then the starter tries to turn it over, but can't. I have replaced the starter, but no luck. Same issue. Last year, this tractor ran fine, and all it has done since then is sit in my basement. This year, this problem arose. Any help? thanks!

06-16-2009, 01:40 PM	#2 (permalink)
Zed101 Registered User Join Date: Jun 2009 Posts: 39 OS: Win XP Prof, SP-3	Re: Briggs 15.5hp engine - locks on compression Just as a routine check, try putting a little oil in the sparkplut hole, turn the enging over a few times. Recheck the plug for depth! It may be the wrong type and goes in too far allowing the piston to hit and not complete its cycle. Just for a test, if you have a shorter plug, wheather it is the correct one or not, try it. If it allows the engine to turn over , Thats the problem! The oil may help the system anyway. Good luck,

06-16-2009, 01:46 PM	#3 (permalink)
dsybert Registered User Join Date: Jun 2009 Posts: 4 OS: win2000	Re: Briggs 15.5hp engine - locks on compression Thanks. The plug clearance is okay. You can stop the engine from turning over by simply putting your finger over the hole. The plug is dirty and gassed, but the gap is still intact. thanks,

06-16-2009, 02:20 PM	#4 (permalink)
usnavyvet Registered User Join Date: Jun 2009 Location: Midwest Posts: 10 OS: Vista	Re: Briggs 15.5hp engine - locks on compression battery ok? I'd check the voltage across the starter when cranking or try a new battery. It could be either a starter or solenoid issue as well. but even if a valve or timing issue, the battery should be able to push the engine through the compression stroke.

06-16-2009, 03:18 PM	#5 (permalink)
k2skier Registered User Join Date: Sep 2008 Location: Oregon Posts: 313 OS: XP Home-SP3 My System	Re: Briggs 15.5hp engine - locks on compression Check valve clearance, about .004-.005, the compression release will not function with excessive valve clearance.

06-16-2009, 07:27 PM	#6 (permalink)
dsybert Registered User Join Date: Jun 2009 Posts: 4 OS: win2000	Re: Briggs 15.5hp engine - locks on compression I tried it with the battery, jumping the battery with a boost pack, and powering it right through the starter, to eliminate the key and everything downline. Still no luck. I will check the valve clearance, but the tractor ran fine last year. The valves shouldn't gain excessive clearance by just sitting for a year. Thanks for the replies. Anyone have any other ideas?