Points check

[ineedanother 1,369]

Bench testing a K301 this evening that had sat for years, reportedly needing a head gasket (which it does, but I digress). Moved the motor onto the floor of the shop and hooked up fuel, battery, wiring harness, and addressed the safety switches. New ignition switch. Crank and no spark. Power at the coil in the run position. Ground wire to points ohmed out. Cleaned the points and still no spark. Changed spark plug. No change. Changed plug wire. Same.

 

I'm getting to my point  This is something I used to do but haven't for years...To check the quality of the ground through the points, take the positive from the battery through a multimeter and check the difference between the base of the points and the ground wire screw with the points closed (ignition off). Today, I had 13.6v from the battery to the base of the points, and 10.6v at the grounding wire.

 

Changed the points and viola! Spark 

[ineedanother 1,369]

I should have added that with new points closed there was no drop in voltage  That was the difference between no spark and good spark.

[Blasterdad 2,692]

I've had "fussy" points send me down a rabbit hole before too, but on the flip side of the coin I usually find something else I don't like.

More often than not unrelated to the ignition system...Lol 

[ineedanother 1,369]

6 minutes ago, Blasterdad said:

I've had "fussy" points send me down a rabbit hole before too, but on the flip side of the coin I usually find something else I don't like.

More often than not unrelated to the ignition system...Lol 

Been there. Going this route I figured I would have isolated the coil and condenser as the suspects remaining but fortunately I had new points on the shelf and those were the culprit  I was somewhat surprised that a difference of 3v prevented any spark at all.

 

 

Edited March 24, 2023 by ineedanother

[kpinnc 12,099]

3 hours ago, ineedanother said:

Been there. Going this route I figured I would have isolated the coil and condenser as the suspects remaining but fortunately I had new points on the shelf and those were the culprit  I was somewhat surprised that a difference of 3v prevented any spark at all.

 

If the coil truly is the internal resistance version, you should only get about 6 volts at the points anyway, correct?

 

So a 3 volt drop would be quite a big drop I'm guessing. 

[953 nut 55,324]

Voltage drop at any point in the circuit is a bad thing. While the ignition points are closed a magnetic field is being established in the coil. At the moment the points open the magnetic field collapses and a momentary high voltage surge comes from the secondary winding and jumps across the gap of the spark plug. If the voltage going to the primary winding of the coil is being shared by the corrosion the magnetic field will only have half as much potential to induce a high voltage in the secondary. Any corrosion anywhere in an electrical system is a bad thing.

9 hours ago, ineedanother said:

I'm getting to my point  This is something I used to do but haven't for years...To check the quality of the ground through the points, take the positive from the battery through a multimeter and check the difference between the base of the points and the ground wire screw with the points closed (ignition off). Today, I had 13.6v from the battery to the base of the points, and 10.6v at the grounding wire.

 

Changed the points and viola! Spark 

Thanks for posting this and we are all glad you got to the point.        

[squonk 41,158]

Make sure the surface of the block where the points attach and where the ground wire attaches will go a long way as well.

[ineedanother 1,369]

6 hours ago, kpinnc said:

 

If the coil truly is the internal resistance version, you should only get about 6 volts at the points anyway, correct?

 

So a 3 volt drop would be quite a big drop I'm guessing. 

I'm not checking ignition voltage. Key off. I'm just comparing the battery voltage grounding directly to the battery as compared to grounding through the ground wire connection on the points set with the points closed.

[ineedanother 1,369]

1 hour ago, squonk said:

Make sure the surface of the block where the points attach and where the ground wire attaches will go a long way as well.

Did that too since it's another place to lose a ground. 

[pacer 3,173]

12 hours ago, ineedanother said:

testing a K301 this evening that had sat for years,

 

Theres your first clue .... when these engines with points sit for long periods the points will all to often get a 'glaze?' on them. And, usually a quick 'wipe' thru them with - most anything, sandpaper, small file, etc.

 

Many yrs ago my widowed mother had one of the early motorized push mowers and after about the 3rd year it wouldnt start - I quickly found there was no spark and and after pulling the flywheel  (the points were behind it) there was no spark. Being at her house and little to no tools, I found a piece of sandpaper and ran it thru them a few times and .... Spark!! Had to do this for annually for some 5-6 yrs.