18 Horse Briggs and Stratton blues

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  #1  
Old 07-06-06, 09:28 AM
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18 Horse Briggs and Stratton blues

I have this older Craftsman riding lawn mower with an 18 horse twin cylinder Briggs and Stratton engin. It ran great when I bought it, but the other day I drove it about two miles(about half an hour). I then turned it off, started it up again, turned it off a few minutes later, and then it would not start. The starter works and it will turn over and everything, but it would not start. The next day, it started right up like nothing ever happened.

Today I started It and mowed my lawn for about 10-15 minutes. I turned it off and now it won't start. Maybe tomorrow it will start? But this doesn't seem normal.
 
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  #2  
Old 07-06-06, 01:20 PM
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msidan,

It's most likely your ignition coil. They can have a small break in one of the turns that when heated by the engine wil disconect. The next time it won't start; remove the breather from the carb and make make sure you are getting gas in the intake and if so; proceed to check for spark. If no spark, it's time for an ingnition coil.

God Bless,
Davbe237
 
  #3  
Old 07-06-06, 01:22 PM
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Try it without the gas cap first.....just to rule out a non venting gas cap.
 
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Old 07-07-06, 08:12 PM
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I already tried it without the gas cap.
I have not had the problem again yet, but I have to drive the mower to where I mow lawns so I can't have this happening away from home.

Anyway, a friend told me that there is an oil sensor that will not let the engine start if the oil is "to old and used". This seems improbable for how old the engine looks. Has anyone heard of this before?
 
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Old 07-07-06, 09:18 PM
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The sensor only prevents the engine from starting when the oil is low. The gas cap would not make a difference because the carburetor has a fuel pump. You could check to see if the vacuum hose is leaking. Also when the engine is cold check the compression, then check it again after the engine gets hot. You may have a blown head gasket , but it sounds more like a lack of valve clearance. Example: The exhaust valve is red hot while the engine is running, heat causes the valve to expand. Without the proper amount clearance between the valve stem and lifter, when the valve expands it makes contact with the lifter preventing it from closing all of the way resulting in compression being blown out the valve port.

NOTE: The clearance can only be checked when the engine is cold.
 

Last edited by mikesmalleng; 07-07-06 at 09:38 PM.
  #6  
Old 07-07-06, 09:35 PM
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Originally Posted by msidan
I already tried it without the gas cap.
I have not had the problem again yet, but I have to drive the mower to where I mow lawns so I can't have this happening away from home.

Anyway, a friend told me that there is an oil sensor that will not let the engine start if the oil is "to old and used". This seems improbable for how old the engine looks. Has anyone heard of this before?
Some have oil sensors, but they only make sure the level is up to full...... no such thing as not letting you start the engine with too dirty of oil on anything..... only thing close would be found on some auto manufacturers, and even then those just pop up with a idiot light telling you to change it, and under different conditions may let you go longer.... or cut the interval short..... they look at rpms and run time etc. May or may not have one, but if it was low.....it wouldn't let the engine run in the first place.
 
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Old 07-07-06, 10:09 PM
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Again,

The oil sensor will only disengage when the oil level is to low and not dirty. Follow the advice I gave you earlier....!

If you are worried about it stoping between jobs; run her at home........ and follow my advice....!

God Bless,
Dave237
 
  #8  
Old 07-08-06, 12:30 AM
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v8driver and Dave are right. You probably have a problem with either the gas cap (no matter whether it has a fuel pump or not, which it does have) or a bad coil. I'm betting on the coil....common failure on these engines. Check for spark next time it dies, immediately after it dies. Carry a plug wrench with you so you can check it as soon as it stalls, before it gets a chance to cool off a bit.
 
  #9  
Old 07-08-06, 02:31 PM
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Well it happened again today. I ran it for about half an hour. After turning it off, it would not start again. I checked both spark plugs, which were working, when I noticed a hose(not the fuel line) that went from the carb to somewhere on the engine(I think it was the vacuum hose that Mike mentioned) that had gotten flattened somehow in such a way that nothing could get through it. I straitened it out by sticking a screw driver threw it, re-installed it, and the engine started right up. I think I will replace it because the heat flattened it out again.

Another thing is that the engine only runs good at about half choke. Maybe this is related to the hose I need to replace?
 
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Old 07-08-06, 04:18 PM
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Glad to hear you found the trouble. This hose drives the fuel pump through vacum in the crank case. As far as running with half choke is concerned you need to clean the carb and if this don't do it you should suspect an intake leak or check the intake valve stem to tappet clearence.

God Bless,
Dave237
 
  #11  
Old 07-09-06, 12:02 AM
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If it is the hose that connects to the bottom of a rectangular part at the front of the carb, it is the hose that pumps the fuel pump diaphragm. Not exactly vacuum, rather...pulses of pressure and vacuum that make the diaphragm go in and out to pump the fuel. If this is restricted, it will not allow the fuel pump to do its job and starve the engine for fuel. Correct this, and then if you still have to keep the choke partially on for it to run right, clean the carb.
 
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