1964 18hp spark fail #1 cyl

[oldomcfan]

I have read all post regarding this issue, but didn't find one like this one. Engine starts/runs good on #2. #1 fires very sporadically one bang at a time. New points, cond., coils may be original but look new and no cracks. New plugs and wires. Carb with new kit, new fuel pump. I was professional chainsaw/weed eater mechanic some 30 yrs ago so am well acquainted with these systems. New to outboards (old OMC's) and am having fun and much success. This one has me a bit stumped so I am pleading for someone to tell me its the coil or cond. I think cond.
Feedback much appreciated.

 

[racerone]

It is not uncommon for a coil to burn through and short out to the magneto plate.----You would have to remove the coil and look on the bottom of the coil.-----But test as follows.----Does spark jump a gap of 5/16" on both leads ?

 

[oldomcfan]

Both coils were removed to replace wires and carefully examined with no apparent fault. I get great consistent spark thru spark tester but have not compared to #2, will do that next. Long ago I had a great lesson about spark plugs. The engine threw good spark to plug, so did extensive, exhaustive analyzing of system, then about to give up, put in new plug...you guessed it So you're thinking more likely coil than cond...?

 

[racerone]

Here I follow my own trouble shooting procedure.-----Those wonderful OMC magnetos are very easy to trouble shoot.

 

[oldomcfan]

I'm looking for your "own trouble shooting procedure" can't find it.

 

[racerone]

When spark jumps a gap of 5/16" then you have " good spark " -----Or I would use a ----MERC-O-TRONIC ----Magneto analyzer to test coils and condensers.------All elegantly simple.----I am not there to see , hear or feel your motor.------Posting specific information only help you !

 

[oldomcfan]

Ah...! Spark jump test is method for this shade tree mechanic
Thanks so much.

 

[racerone]

Laying plugs on the block is a waste of time !!----I learned how to trouble shoot these simple magnetos 52 years ago.

 

[oldomcfan]

I cringe to belabor this thread, however do to Mr racerone's kind help and my need to solve this fault as cheaply as possible, I continue.
My new spark tester's electrodes appear to be only around 1/16 gap; with this connected and engine running on #2, a hot, consistent spark shows on #1. So would I widen the gap on old spark plug to 5/16 to test? My tester is the closed bulb type, not the spark plug type.

Forgot to mention early on that cyl compression is 80 on 1 and 85 on 2.

 

[racerone]

The magneto was engineered and built to be able to produce about 28,000 volts if in good condition.----That voltage will jump a 5/16" gap with a SNAP you can hear.------Sorry it does not take much voltage to jump a gap of 1/16" or so.-----And it does take more voltage to jump a plug gap when the plug is in the cylinder and air is compressed.----A spark gap tester is easy to make with some wire / carboard / glue.----Proper testing is the path forward !

 

[Crosbyman]

what ohms resistance do you measure on your coil secondaries at the boot end of the spark wires

use the proper scale (above the expected reading) ex: 10,000 ohms scale if using an analog (needle) meter (digital meters will self adjust)

 

[oldomcfan]

Much thanks for all the good advice here. Coil test showed no fault so decided to replace the condenser. Coil looked and tested excellent and condenser was brand new in set with points. New condenser was bad, now all is well. Especially pleased with the cardboard, wire and glue spark tester Mr. racerone.

 

[Crosbyman]

This month's OUTBOARDER magazine to AOMCI members has a good article on building a condenser tester which I have decided to build...to keep me busy during the months ahead even if the cost ...would have allowed me to buy quite a few condensers

Some parts coming from China (Amazon) but as soon as I finish the project i'll report back.

 

[oldomcfan]

Sounds like fun...I'm in