1966 20 HP Johnson no fire top cylinder

[heypawpaw]

Coil tested ok so changed points still no fire. Put in new coil and no fire. Reading continuity on plug wire. Thinking condenser next thing am I missing something.

 

[jbuote]

Not a pro myself, and I'm sure you did, and I'm sure you know, but just to ask so it's out of the way....

When you put the new points on, you did clean and set the gap on them right? ( 0.020 max I think it is?? :noidea
Even new points have a film on them and need cleaning.. (As you know, I'm sure...)

I'm guessing yes to all of the above, but just so it's asked and clear.... LOL...

 

[flyingscott]

Points and condensers should be replaced as a set. Most of the time it is the condenser the is bad.

 

[Crosbyman]

basic magneto... (btw keep that old coil because it wasn't the problem !)

if and if it is a condenser just swap it with the other one... if the problem follows the condenser change the condenser !

http://www.leeroysramblings.com/Johnson_troubleshooting.htm
http://www.leeroysramblings.com/johnson_magneto.htm

 

[heypawpaw]

Thanks guys. Yes I changed and cleaned both points and set to 020. Bottom cylinder jumps 7/16 gap as before but no change in top. I picked up the points and coil a while back to have on hand but didn't think about condenser at the time. I'll swap condensers and go from there,

 

[jimmbo]

Possibly a grounded primary circuit, an ohm meter will determine if opening the points does break the path

 

[Crosbyman]

Thanks guys. Yes I changed and cleaned both points and set to 020. Bottom cylinder jumps 7/16 gap as before but no change in top. I picked up the points and coil a while back to have on hand but didn't think about condenser at the time. I'll swap condensers and go from there,

a bit of work but you can also try to switch the coils around but if you swap things swap only one component at a time

if no change return the part to its original position and try another component

jimmbo is correct... do check the coil green wire for rubbing on the crankshaft and make certain the coil black ground wire gets a good ground on the lamination screw/bolt (scrape away any paint )

 

[F_R]

You are being a bit overly optimistic if you expect that thing to jump a 7/16" gap. Try again at 1/4", and if it will do that, you are good.

 

[heypawpaw]

Went out this morning swapped condensers no change. Removed armature plate and inspected plug wires noticed wire not firing had chafing in insulation where clamped under armature plate. Didn't look completely broken but thought it may be grounding so cut off bad piece of wire and reattached to coil. This time it had fire but had short intermittent no spark periods. Pulled off spark plug boot and cut end of wire and reattached boot and now have good continuous fire. Now I have to get new plug wires as they are too short now.

 

[heypawpaw]

Sorry FR I measured again and its 5/16 gap I wrote it wrong.

 

[oldboat1]

Sticking the spring clip spike through to the solid core, right? (7mm solid core wires, not the automotive type.) You can check resistance from the clip through the coil, to the mag plate -- getting a reading is a way of insuring you have a connection.

 

[heypawpaw]

Plug wires have a stranded metal core not solid. Skinned back insulation exposing about 1/8" of wire folded wire up put spring clip against wire and pierced pin through core and slipped boot on. Haven't got new wires yet but will get OMC or Siera 7/16 marine ignition wire.

 

[heypawpaw]

Jimmbo are you saying check continuity between plug wire and ground and if circuit broken when points open ok and if continuous continuity primary grounded?

 

[Crosbyman]

booth to engine frame ground should be 4-7 K ohms if coils have ascrew type terminal screw the strands on the HV screw pin

points open or not you must read 4-7 kohms booth to frame grd

 

[jimmbo]

I had said to check the wiring on the primary side for shorts to ground which would render the points ineffective. But since you now have spark it shows the points and the rest of the parts are functioning.

 

[heypawpaw]

Installed new plug wires and new condensers now all is working properly. Put old coil from this engine on my 20RL70 as it had a coil shorted on primary side and now both working ok.