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8 hp 2 stroke won't fire

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mmather243

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This is a Yamaha motor. Last time the engine ran I was approaching the boat launch and the engine started to die. I could keep it running by choking it. You would think I was running out of fuel or the tank was venting, right? However, this spring she won't fire at all. I thought that maybe the kill switch was bad, but the behavior the last time it ran makes me think that either the ignition module or coils are the problem. I hear this is the best place for advice. What say you guys?
 
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mmather243 said:
This is a Yamaha motor. Last time the engine ran I was approaching the boat launch and the engine started to die. I could keep it running by choking it. You would think I was running out of fuel or the tank was venting, right? However, this spring she won't fire at all. I thought that maybe the kill switch was bad, but the behavior the last time it ran makes me think that either the ignition module or coils are the problem. I hear this is the best place for advice. What say you guys?
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Have you been running ethanol blended gas in it? If so that is probably your problem. By choking the engine you were manually feeding more fuel to it through the carb that was probably clogged and couldn't deliver enough fuel without choking it.

Buy a couple of cans of jet spray carb cleaner (carb cleaner is cheap and the outboard service center is expensive). Pull the carb, take it all apart (everything you can take apart including the little brass fuel jet and fuel bowl taken out & off) and blast that carb cleaner through every orifice you can find. Check the little hole in that brass fuel jet and make sure it is perfectly clean and clear. If it isn't, run a little piece of COPPER wire through it (softer than brass) and clean out any gum the carb cleaner spray couldn't blast away.

If there is old ethanol blended fuel in your tank get rid of it. How you dispose of it is your own business (have a trash pile that needs burned?) Put fresh fuel in, hook up the fuel line and pump the bulb with someone back by the engine to catch the fuel in a cup as it squirts out from the fuel line that would feed the carb you've pulled and have cleaned. Keep pumping and squirting to get all that old fuel out of the lines.

Put it all back together and then re-pump the fuel bulb until you get resistance and it is hard as that means the fuel bowl is filled. Then, see if she fires up.


An engine is simple... you need air, spark and fuel.
 
I'm getting fuel in the cylinders. Plugs aren't firing.


deepsea21 said:
Have you been running ethanol blended gas in it? If so that is probably your problem. By choking the engine you were manually feeding more fuel to it through the carb that was probably clogged and couldn't deliver enough fuel without choking it.

Buy a couple of cans of jet spray carb cleaner (carb cleaner is cheap and the outboard service center is expensive). Pull the carb, take it all apart (everything you can take apart including the little brass fuel jet and fuel bowl taken out & off) and blast that carb cleaner through every orifice you can find. Check the little hole in that brass fuel jet and make sure it is perfectly clean and clear. If it isn't, run a little piece of COPPER wire through it (softer than brass) and clean out any gum the carb cleaner spray couldn't blast away.

If there is old ethanol blended fuel in your tank get rid of it. How you dispose of it is your own business (have a trash pile that needs burned?) Put fresh fuel in, hook up the fuel line and pump the bulb with someone back by the engine to catch the fuel in a cup as it squirts out from the fuel line that would feed the carb you've pulled and have cleaned. Keep pumping and squirting to get all that old fuel out of the lines.

Put it all back together and then re-pump the fuel bulb until you get resistance and it is hard as that means the fuel bowl is filled. Then, see if she fires up.


An engine is simple... you need air, spark and fuel.
Click to expand...
 
How did you check for spark? Are you absolutely certain you are not getting spark? Are you willing to pull the plug wires from all plugs, stick you finger in them touching the copper cap inside, and let someone else give the engine a pull with you finger stuck in the plug wires? Lots of people say they get no spark but they pulled the plug, put the wire on it and tried to ground the plug to some part of the engine (which has is usually painted and paint = no good (-) ground).
 
Also remember... Old stale fuel will not fire. Your plugs may be wet but they can be wet with old stale fuel that will not fire. Another way to check for spark is to buy a can of engine starting fluid. Pull each plug and spray some starting fluid in the cylinders one by one replacing each plug as soon as you've sprayed into that cylinder. Then, give it a crank and see if it fires one or two times. If it fires just once or twice with a few kicks, you have spark.
 
starting fluid is not a good idea guys It has no lubricating properties!Can damage engine.But it does work. Build a spark tester or buy 1 at auto part store.
 
johnnygjr said:
starting fluid is not a good idea guys It has no lubricating properties!Can damage engine.But it does work. Build a spark tester or buy 1 at auto part store.
Click to expand...

I personally wouldn't worry about it if spraying it into the cylinders themselves just to check for spark and if it will fire with some starting fluid introduced. I would not however, spray it into the air intake and keep spraying it after the engine has fired and is running on starting fluid (seen people do that) as it will keep running as long as you keep spraying that fluid into the intake which means no fuel-oil mix being introduced to the cylinder if there is a fuel blockage issue.
 
I will also say with regard to pulling, breaking down and fully cleaning the carbs - Every beginning of the season before you start the engine, back out the little brass fuel jets in the carbs and check that their orifices are ABSOLUTELY CLEAN AND CLEAR. Blast carb cleaner through them - Copper wire if needed (learned this the very hard & very expensive way)... A fuel jet can have that orifice clog say just say 25% or 30%. The engine will start and seem to run fine (especially in a multi cylinder engine) but the reality is that cylinder is running 25%-30% lean which means 25% to 30% less fuel/oil mix which means it's not getting the lubrication it needs throughout the RPM range. That = a scored cylinder wall, burned rings or a melted piston head which = expensive reboreing of that cylinder and re-ringing the piston. An engine is good for one costly re-boring and re-ringing. Score a cylinder after that you have a new new anchor for the boat as the engine is toast. All that can be prevented by taking 15 minutes and checking those jets at the beginning of every season and, of course, adding marine fuel stabilizer to your fuel ALL THE TIME... Not just prior to storage!
 
get a spark tester or build one with nails and a piece of wood.You should have a video diy.You said its getting fuel, Are plugs wet with fuel and oil?age of motor?hours on engine,new fuel in tank? I meant You tube might have a video on constructing spark tester.
 
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