# 18 HP Briggs Shuts Down 20 Minutes



## smitty210 (Jul 27, 2010)

I have the same problem many others had. I have a Craftsman 18HP BS #31H777-0297-E1. Will start and run about 20 min. then shuts down. Sit 5 min. it starts and gets back to garage. Things I have done.
New plug
New Air Filter
Adjusted valves and re-checked 4 times.
Replaced coil.
Cleaned fins and checked oil level.
Pulled Carb. Cleaned. Checked shut off valve in bowl. 
Set Valves at .005 both int. & exh. Then 2nd time set int. at .004.
Seemed to start better. Before it would not turn over without jumping.
Set coil/flywheel clearance at .010, ran for 37 minutes then shut off.
Found sticking chock in carb. Wired open just to check, no difference. 
Noticed smoke coming from carb once when I shut it down.
It did fine sine 2004( model year) till I cut down some flowers. I hit an old ant hit and mower nearly stopped. Finished mowing, about 2/3 acre and did fine. Next time I mowed It sputtered and shut off about half way trhu mowing ( 30 min.) Thinking about putting plastic plug in carb. bowl.
Anyone have any suggestions?


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## K-B (Oct 24, 2005)

When it starts to shut down, try choking it and see if it continues running for a few extra seconds. Also, as soon as it shuts down check the spark. It's also possible that the vent in the fuel tank cap is plugged. Either try a new cap or try opening the cap when it starts to shut down and see if it continues running.

EDIT:
Check the flywheel key also, I'm not sure how that could cause your problem but it's possible that it sheared or partially sheared when you struck something.


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## smitty210 (Jul 27, 2010)

Tried chocking, dies anyway. I ran it about 20 minutes without the cap, still shut down. It does have a spark within seconds after it shuts down.( next time I'll wear gloves, gets hot). Have thought about key but I didn't check it because I didn't see how it would run at all. Also in my parts book, there is no key mentioned, only two bolts. Do some of these use bolts instead of keys? Any way I will check. At this point I am willing to try most anything. Is it possible the solenoid could work at times and just quit at times?

I did hit that old ant hill pretty hard, and it was pretty hard too after all the rain then the sun coming out as hot as it did.


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## K-B (Oct 24, 2005)

I wouldn't expect it to continue running with the choke, I just wanted to find out if it would run for a few seconds longer.
It certainly does have a key...part number 222698S. Engines will sometimes run even if the key is slightly sheared, although poorly. They would usually be hard to start, backfire, run rough or not go up to high RPM.

Do you mean the fuel solenoid? If it is equipped with one, that certainly is a possibility.If you can't find an appropriate plug, try Briggs # 691657, (not sure if that plug will work if that engine has a Nikki carb). Or just replace the solenoid, #694393.


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## smitty210 (Jul 27, 2010)

Thanks for your input. I didn't have either of those numbers. I have some Honey-dos right now, but from what you've told me I think the key is the culprit. I'll pull the flywheel tomorrow and check it. May be late afternoon before I can get back, but I'll let you know what I find. It has backfired a couple times and does not run as smooth as it once did. 


Sorry I forgot, It died immediatly when I chocked it.

Thanks for your help


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## smitty210 (Jul 27, 2010)

I'm back. This may be a little premature, hope not. I haven't had time to pull the flywheel yet, but I did manage to replace the fuel solenoid with a plug. It has been running 1 hr. 3 min. as I am typing. I mowed the back yard ( 140 X 100 Ft.) parked it and it's still running. I mowed at a lower rpm, just to put more load on it. Seems to be ok at this time. I plan to put a manual fuel shut off on it to be safe. 1 hr. 8 min. now. will let it run until the gas in the tank is gone. As I say, it may be a little premature, but it looks like the fuel solenoid was the problem. I appreciate all your help.


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## K-B (Oct 24, 2005)

Good, hopefully you've nailed the problem.

The fuel solenoid does not shut off fuel to the carburetor, it only shuts off fuel flow to the main jet to prevent or minimize backfiring on shutdown. So installing a inline fuel shut off is not necessary.


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## smitty210 (Jul 27, 2010)

Well, it ran out of gas. About 3/4 tank. That's about what it takes to mow my yard. Put gas in it and except for the starter clicking a few times, it started up and ran just fine. Thought I had the starter problem solved when I adjusted the valves. I'll tackle that another day, but I think I'm ready to confirm that it is fixed.
Again, thanks for the help.


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