31P777-0296-E1 Question

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  #1  
Old 07-16-14, 10:21 AM
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31P777-0296-E1 Question

I was getting ready to put a new camshaft in this engine. The starter does not have enough power to turn the engine past the compression stroke. The valves are adjusted correctly and the keyway is good. Here is the puzzling part and why I posted this -- If I turn the engine backwards until I hit the compression stroke and then try to start it, the starter turns it over fine. With the key off it will turn and turn and turn. Is the camshaft / compression release really shot or is it the starter ????? It will not turn it past the compression stroke from a dead start. Why is it able to get by the compression stroke once it starts spinning ?????
 
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Old 07-16-14, 03:04 PM
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Before I would start going at the camshaft I would remove the valve cover and remove the spark plug. Now turn the flywheel very, very slowly and observe the intake valve carefully. What you should see is the valve open and then close and if you keep turning the flywheel slowly you should see a very, very small bump in the valve. That bump is the compression release working as it should. If you do see the bump, I doubt you have a camshaft problem.

Now if it is not the camshaft it could be your carb flooding. I am not sure what you mean by "with the key off it will turn and turn and turn". With a flooding condition, where gas is sneeking by the inlet needle of the carb, when in storage, the liquid gas can get into the combustion chamber and the hydrolock tension from the gas along with the compression will sometimes stop the crank at the compression stroke and give the impression that your compression release is not working. Usually the motor will slowly crank past this and then because it is flooded, crank and crank and crank and sometimes start and sometimes not. Does this sound like your motor?
 
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Old 07-16-14, 05:13 PM
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Thanks for your response.

Sorry, I need to clarify the key off situation. I hook my jump start battery box directly to the starter. I can then leave the key off and the engine will not start however the starter turns it over fine if I turn the engine backwards to the edge of compression prior to engaging the starter.

The carb needle / seat is not leaking.

I am trying to figure out why the starter can turn the engine over with no trouble when I turn the engine backwards prior to engaging the starter but cant budge it past the compression stroke if I don't. Could the energy created from the flywheel turning give it the extra boost to continue to crank the engine ??? It has a heavy cast iron flywheel with a steel ring gear.

This is the third 18.5 HP Briggs Intek I have run into with this problem. The problem seems to be only with the 18.5 HP engines. I have not seen this problem on other Briggs Intek engines. On those it is always the valves.
 
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Old 07-16-14, 08:51 PM
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I would check the valve movement as suggested to make sure the cam is bad. The ignition of the gas in the cylinder is making it harder to start. The starter isn't turning it with no problem if you;re having to back it up like that. It is just barely getting enough of a running head start to barely overcome the compression. Once it does that, the flywheel is going fast enough to do it's job and help the engine continue spinning with much less effort from the starter.
 
  #5  
Old 07-17-14, 02:41 AM
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I had a feeling that the heavy flywheel allowed the starter to keep turning it. I guess I will go ahead and replace the camshaft. Oh how I dread removing that double pulley.
 
  #6  
Old 07-17-14, 04:51 AM
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You're pretty sure that BOTH the Battery and the Starter are in good condition ?

I just replaced a Battery which I had falsely accused of going bad after 7 years, when it was actually the starter which had begun binding. A new starter solved my problem; so now I have an extra battery.
 
  #7  
Old 08-19-14, 04:38 AM
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Well, I put a serviceable camshaft in the engine yesterday. I was dreading getting the double pulley off however it came off with little to no resistance. The engine fired off and ran fine. What a difference in starting now. All in all not too bad of a job. Most PITA part was scraping off the sump gasket. Will be checking for any leaks today.
 
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