no spark on one cylinder UPDATE!!!!

[tx1961whaler]

Re: no spark on one cylinder

Re: no spark on one cylinder

There is a valid part number for a 581109 flywheel for a 1974 25hp. Not finding a 581105 part number for anything. I'm trying to figure out why having a 2 magnet flywheel would do bad things to a universal type magneto setup and prevent one cylinder from firing. I would think that if something is way off with the spark timing, it would affect both sides of the ignition equally. Normally a two magnet setup has only one coil under the flywheel and the points switch the drive voltage between the two external coils.

 

[bare3176]

Re: no spark on one cylinder

Re: no spark on one cylinder

Does the 581109 have two magnets? Do I need to try and find an older flywheel? How can I identify what I have, meaning a diff. powerhead on a 74 body?

 

[tx1961whaler]

Re: no spark on one cylinder

Re: no spark on one cylinder

It looks like some thing is mismatched. The flywheel seems to be the proper one for a 1974 (two magnet), but the armature plate seems to be from a 1972 or earlier. I do not know for certain if a 1972 flywheel would fit.

There is sometimes a model number on a round silver plug on the powerhead, but most Johnson's seem to only have the serial number on it. If there is only a serial number on it, you can see if it at least matches the one on the transom tag.

 

[bare3176]

Re: no spark on one cylinder

Re: no spark on one cylinder

I worked on it again this evening and nothing. I swapped the points, and still just a weak spark thru the plug, nothing thru the tester. Something is wrong and isolated to the bottom cyl. I stopped by an old local boat mechanic today and ran it by him, and he had nothing to allow that I haven't already tried. I went to the lake and got my 72 20hp and swapped the f/w and nothing different. Is there something missing like some type of insulator that could be allowing the points to ground out? Any help would be appreciated.

 

[bare3176]

Re: no spark on one cylinder

Re: no spark on one cylinder

I forgot to mention that the power head is a different color than the rest of the motor, it's kind of blue where the rest of the motor is greenish. My 72 is all the same green. The plug with the serial # is missing on the 25.

 

[Daviet]

Re: no spark on one cylinder

Re: no spark on one cylinder

I know we are grasping at straws here to try and figure this out, so I am going to throw this out there. Way back when I had an 18hp that had weak spark on one cylinder, went through all the standard stuff and no help. What fixed my problem was to remove the points and clean the base of the points and the contact area of the mag plate with some emeroy cloth to make sure I had a good ground for the points. I know it sounds foolish, but nothing else has worked so far.

 

[bare3176]

Re: no spark on one cylinder

Re: no spark on one cylinder

Hey nothing sounds foolish at this point, I'll try that tomorrow, Thanks.

 

[Daviet]

Re: no spark on one cylinder

Re: no spark on one cylinder

Holding my breath, hope it works.

 

[bare3176]

Re: no spark on one cylinder

Re: no spark on one cylinder

Well I tried sanding the points and the plate, cleaned everything again with solvent, put it back together and still a weak spark thru the plug and nothing thru the tester. I am at a loss..........

 

[Monte1961]

Re: no spark on one cylinder

Re: no spark on one cylinder

Dumb question. Was the condenser changed out? Just a thought!

 

[AlTn]

Re: no spark on one cylinder

Re: no spark on one cylinder

good thought, Monte....swap condensers and see if spark quality changes on each plug

 

[bare3176]

Re: no spark on one cylinder

Re: no spark on one cylinder

I swapped the points and condenser from one side to the other, keeping the condenser with the same set of points, and no change, just weak thru the plug.

 

[AlTn]

Re: no spark on one cylinder

Re: no spark on one cylinder

new terminals and boots on plugwires? <wondering if the spike on the #2 wire missed the inner wire slightly?>...

 

[bare3176]

Re: no spark on one cylinder

Re: no spark on one cylinder

I can get continuity from under the coil to the metal part that snaps to the plug. Everything is new.

 

[AlTn]

Re: no spark on one cylinder

Re: no spark on one cylinder

reread this thread and ,as I understand it , the coils haven't been replaced and this motor ran for 15 minutes before the #2 cylinder lost spark?..#1 cylinder has always had good spark....have you tried switching the coils only, no other component of the ignition system, and, if so, what was the result?

 

[bare3176]

Re: no spark on one cylinder

Re: no spark on one cylinder

Yes the coils haven't been replaced. I put it back together with a weak spark thinking that was the best I could do and it ran for 15min. yes #1 cyl has never lost spark no matter what I do, and yes I have swapped just the coils with no change.

 

[bare3176]

Re: no spark on one cylinder

Re: no spark on one cylinder

Can ya'll think of anything else? Thanks for all the help.

 

[bare3176]

Re: no spark on one cylinder

Re: no spark on one cylinder

Somebody told me today that the circuit that is not firing has to be grounded, but I don't have any idea where it could be. Should I try and put some thin plastic under the coil, the points, the condenser? Where could it be grounded that wouldn't change when I swap every part under the F/W and still get a very weak spark thru the plug and nothing thru the tester? Thanks again for all the great ideas. Sorry if I come across a little harsh sometimes I just can't stand not being able to fix this motor.

 

[tx1961whaler]

Re: no spark on one cylinder

Re: no spark on one cylinder

Sound like good ideas. I'm out of ideas, other than using the ohmmeter to probe around and compare readings between the good side and bad side. Maybe you'll find something sorted to ground or each other.

 

[penn1974]

Re: no spark on one cylinder

Re: no spark on one cylinder

i have the same problem butt i seen te question earlier about have u swaped the wires coming out from under the f/w and put them on the opposite coil.Well i did and neither one fired then.So anybody got any suggestions on that.It's a 74 johnson 9.9.