Great Spark But Won't Fire ...

[bobgritz]

I picked up a cheap Mercury 9.8 HP (Mod. 110) and seller said it sat for quite a while and wouldn't keep running and needed carb rebuild. He squirted starting fluid in carb throat and vroooom ... it fired right up for about 2 seconds. Terrific. EZ fix. Got it home, left it on the garage floor for about 2 weeks and when I mounted it on engine stand, it wouldn't pull over, the cylinders were stuck. I applied Sea Foam, and with a little coaxing the cylinders were free. I pulled it a dozen times (w/o plugs) to get rid of Sea Foam. The sparkplugs looked great and they had a healthy spark. Put them back in and it pulls pretty easily but now I can't get any sign of life! I have tried spraying with starting fluid, I have removed plugs and sprayed directly into cylinders and putting small amount of fuel directly in cylinders. I'm getting a nice spark but can't even get a 'pop'. The only thing I can figure is that I somehow misaligned the flywheel's timing when it got locked up. I had removed the pullstarter and used a catspaw to apply a little persuasion to the top flywheel/crankshaft but I was pretty careful not to overdo my force. I just cannot understand why it won't even give me a tiny pop. My arms are getting worn out. HELP.

 

[Jake_MN]

Re: Great Spark But Won't Fire ...

Avoid starting fluid. Especially repeated use of it as it does not carry lubrication and can even strip the protective coat of oil from the cylinders. I wouldn't doubt if the previous owner had repeatedly used starting fluid to start it and as such de-lubed the cylinders contributing to your locked-up engine.

Now that you have the engine free, have you checked compression? Have the carbs been rebuilt yet? If so, do you know that you are getting fuel in the cylinders?

 

[bobgritz]

Re: Great Spark But Won't Fire ...

Thanks Jake ... I agree that starting fluid is never recommended and it was used only for demonstration since the carb was assumed to be gummed up ... it's a valuable method that helps to pinpoint problem areas such as a foul carb. He's a shadetree mechanic and knows enough about the dangers of using ether-type solvents. I have introduced both gas & evil starter fluid directly into a) the carbs' throat and, b) directly into the cylinders with absolutely no sign of any life. Compression registers fine. I have not yet rebuilt the carb because it may not be the problem.

 

[merc850]

Re: Great Spark But Won't Fire ...

Check to see if the timing is right - remove plugs and ground them to the block. Use a pen in the Nr.1 cylinder and turn engine over by hand until the piston rises to the top, rock piston back and forth and watch for spark; this will show whether the spark is occuring at the right time. (Should be near TDC)
Post the serial Nr. so that further info can be given.