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20HP wonbt start strange

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"Fellow Mercury enthusiasts -

"Fellow Mercury enthusiasts -

My 20HP 2-stroke engine (can't figure out the year but S/N is 0C297048) now refuses to start cold.

I'm no mechanic, but I have done basic things to diagnose: It does not appear to an issue with the carburetor because I can see fuel going in there. When I remove a spark plug after several pulls, the spark plugs (which are new) are dry. However, if I deposit just a little bit of fuel in the combustion chamber and replace the carburetor, the engine starts right away and keeps going as if nothing was wrong. Furthermore, I can now stop and start the engine with no trouble.

So, forgive my n00bie ignorance here, but could it be (1) lack of vacuum in the chamber due to a bad gasket or (2) a piston gone bad or something entirely different? Am I out of my league here?

Appreciate any input.

Tony"
 
"Tony, that is a 1990 model. O

"Tony, that is a 1990 model. Outstanding motor by the way...

Sorry, have to ask - you are choking the motor when you start it cold??

Best to make sure of the starting proceedure before you get out the wrench and screwdriver..."
 
"Re: Choking - yes absolutely,

"Re: Choking - yes absolutely, although lately I'm thinking that strangling would be a better option."
 
"Ok then, first would suggest

"Ok then, first would suggest that you look down the carb throat when you pull the choke knob - you should see a shot of gas dump right into the throat.

It's possible that the diaphram on the primer has gone bad on you.

When you pull out the choke a kinda finger presses the priming plunger located on the right side of the carb - just make sure that it appears to be operating properly before going any further."
 
"Update: I purchased and insta

"Update: I purchased and installed a new diaphragm - the old one indeed went bad. I replaced it making sure the gasket fit securely.

Sadly, even with this I could not get the motor to start. After repeated attempts (choke out, choke in), I removed the spark plugs and they were completely dry, so no gas is going into the combustion chamber.

I tested the vacuum effect by removing a spark plug and putting my palm in the opening while my dad pulled the starter. There is indeed a vacuum formed.

Somehow the fuel is not making it into the chamber.

Thoughts?

Tony"
 
"It's worth checking, thou

"It's worth checking, though I've never been that "deep" into the engine before. I'll try this weekend. Thanks.

Tony"
 
"put your hand over the carb a

"put your hand over the carb and try to start, no vacuum would be seal or reeds,if there is vacuum maybe plugged idle speed jet. I don;t see how it could be reeds when you say it was runnin in your first post"
 
"Ok problem solved - in the en

"Ok problem solved - in the end it was a combination of 3 factors (in addition to the bad diaphragm which I had previously replaced): (1) the fuel had gone somewhat stale (2) the lower cylinder was not firing and (3) one of the reeds was indeed gummed up.

Thanks Graham, and JB for all the help."
 
"Posted too soon. After having

"Posted too soon. After having stayed away for a few days, engine won't start this morning. : (

Tony"
 
"The link rod for the fast idl

"The link rod for the fast idle is on correctly? There is a plastic arm on the left with a rod that goes to the spark advance (trigger base) under the flywheel. (When you turn the knob to raise the fast idle.) The L end of the rod must point up. If the rod is not pulling the spark advance, the motor will be hard starting cold."
 
The ony way to see if the prim

The ony way to see if the primer works is with the carb off the motor. The gas comes out of a hole in the flange and right into the reeds.
 
"It is possible that a weak ig

"It is possible that a weak ign system will do this. Do all the DVA checks for low voltage. Oh, wait 5 seconds between pulls on tha knob. "
 
The motor seems to be starting

The motor seems to be starting reliably now - I also added a fuel filter just to make sure the system doesn't get excessively gunked up.

Thanks for all the help.
 
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