spark but no spark

[tmryan]

I recently was given an old outboard motor.<br /><br />When I try to start the motor, I get a very weak spark. The previous owner has told me that he replaced the points and condenser.<br /><br />Since I do get a spark, what else could it be other than the point/condenser. Would the coil work at a lower level. I always thought coils worked or did not work. What other componets could cause a weak spark. Are there any tests to isolate the cause.<br /><br /><br />The motor is a 5 hp.<br /><br />Thanks, Tomr

 

[petryshyn]

Re: spark but no spark

very common to have weak spark from coil...<br /><br />>coils can be tested with a Ohmmeter, but the results are sometimes inconclusive, especially if you have some spark. Its usually best to have the coil tested at a small engine or marine shop. Look for any visible cracks, burns etc. If none, get it tested...they have a signal generator that they apply.<br />>what color is the spark?<br />>will it jump a plug gap?<br />>will the engine run?<br />>are the points clean? dirty points > weak spark

 

[tmryan]

Re: spark but no spark

I get very weak spark. Can see it when I use my spark plug tester (you know one of those $5 part that you connect between the plug and the plug wire). Even when I bare hand the wires, I get only a minor shock.<br /><br />The points and condenser are new.<br /><br />What type of reading should I get using an ohm meter on the coil.

 

[petryshyn]

Re: spark but no spark

Hi tomr<br /><br /><<<<Typical mag coils>>>><br /><br />(disconnect lead from points....)<br /><br />>Primary = .5 - 1.5 ohms from point lead to core material (or ground wire)<br /><br />>Secondary = 5000 - 9000 ohms from plug wire to core material (or ground wire)<br /><br />Again, these specs can be misleading, because they will not show up a interior cross-fire or leakage which can lead to weak spark. I'm not sure of your tester, so how about taking an old plug and connecting the plug wire to it, and hold it tight to engine block. Get someone to pull it over as fast as possible and see if it jumps the gap.

 

[Yepblaze]

Re: spark but no spark

You might be suprised what a good spark looks like on some motors. Especcially some of the small japanese stuff. You want to test the spark to see if it is strong enough to run? Just squirt a little premixed gas in the cylinder and screw the plug back in. Give it a few pulls. If it fires off for a moment then dies, start looking at fuel problems instead.

 

[JIM MAW 2]

Re: spark but no spark

Is it possible that the new points still have<br />the protective coating on them...ie not cleaned before or after installing them ?

 

[JB]

Re: spark but no spark

Ahoy, Tom. After all these posts, it would be useful to know the brand and model of your engine. I have figured out that it is a single cylinder. Is it air cooled or water cooled?<br /><br />You may be getting a "maverick" spark, in which spark is generated directly into the coil secondary by the flywheel magnets. That could happen if your points are not grounding the primary winding and allowing it to store energy to be released to the secondary when the points break. It can also happen if the primary is open. As Jim Maw suggests, you would get this if the points are closing but failing to make electrical contact.<br /><br />Use a meter. Confirm that the points are really closing and are gapped properly.. . .probably .020, but some magnetos wanted .010 to .012.<br /><br />Red sky at night. . .<br />JB