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Need help! No spark on one cylinder.

B

BigNate

New member
Howdy folks, newbie here, first post. I've purchased an old Skeeter with a 1979 Johnson 115 bored to 140. Motor ran so-so. I cleaned carbs and it ran much better but still only felt it was at 75percent of it's potential. I drained tank and gave it some new premix. Motor fell on its face on the water....brought it home and it idled fine both high and low rpm in a bucket. Then it started back firing out the exhaust. When at a low idle it would backfire and die.i pulled plugs and found a mess on the top starboard plug, all the others were ok. Changed plug, no difference. Bought new coil, didn't help. New power pack, didn't help, new stator and guess what???? Didn't help! So I've checked compression in all 4 and each one is 80.5 or 81. So I've got equal compression x4, good spark x3 and my hair is getting grayer by the minute.

Will the timing trigger cause no spark on just one cylinder? Suggestions PLEASE!!! IM ABOUT TO MISS THE BASS SPAWN!!!
 
How do you bore out a 115 HP to 140 HP , just curious.----Swap powerpacks from one side to the other and report what happens.----The term " Good compression " means nothing here.-----Post the actual numbers you have today.
 
Copied from the CDI Ignition troubleshooting guide for your motor:

NO SPARK OR INTERMITTENT SPARK ON ONE CYLINDER OR ONE BANK:1. Disconnect the stop wires from both power packs and retest. If spark returns, swap the power packs and reconnect the stop circuit. If the no spark problem remains on the same bank, the stop circuit has a fault. If the problem moves, replace the power pack that was firing correctly due to a bad blocking diode in the pack.2. Swap the stator wire pairs from one side of the engine to the other side and see if the problem moves. If it does, the stator is bad.3. Check the stator and timer base resistance and DVA output on BOTH banks (see NO SPARK ON ANY CYLINDER above).4. Check the DVA output on the Orange wires from the power pack while connected to the ignition coils. You should have a reading of at least 150V or more. If the reading is low on one cylinder, disconnect the Orange wire from the ignition coil for that cylinder and reconnect it to a load resistor. Retest. If the reading is now good, the ignition coil is likely bad. A continued low reading indicates a bad power pack. 5. Visually inspect the ignition coils for burned or discolored areas and cracks in the casing (indicating arcing inside the coil). 6. Swap the ignition coil with one that is sparking correctly.7. Rare causes include a weak trigger magnet. If possible, try another flywheel
 
Well , Missed the 80 PSI compression.----This means the gauge is junk or the motor is in bad shape.-----Load test the battery even if it is new.----Take starter apart for inspection service.-----Low cranking RPM can lead to spark missing on 1 or more cylinders
 
racerone said:
Well , Missed the 80 PSI compression.----This means the gauge is junk or the motor is in bad shape.-----Load test the battery even if it is new.----Take starter apart for inspection service.-----Low cranking RPM can lead to spark missing on 1 or more cylinders
Click to expand...

Starts with vigor. Brand spanking new battery with plenty of starting rpm. It's a brand new digital compression test kit. 80 seemed a bit low to me as well but still didn't make sense as to why there wouldn't be spark.
 
Mentions the stop circuit....how do I know which ones are the stop wires? I'm new to engine mechanics and want to learn as much as I can. Sorry for the handicap in not knowing what it's referencing.
 
racerone said:
How do you bore out a 115 HP to 140 HP , just curious.----Swap powerpacks from one side to the other and report what happens.----The term " Good compression " means nothing here.-----Post the actual numbers you have today.
Click to expand...

Before I purchased the new power pack I swapped the port side over to the troubled starboard side and found spark on the problem cylinder. That's why I purchased the new power pack and installed it. Then that new power pack shows no spark on the same problem cylinder as well.
 
If you want to work on outboards effectively a factory (OMC) service manual is a must. Do not bother with an aftermarket manual! You can PM me with your email address and I will send you a PDF copy of the CDI ignition troubleshooting guide which is nice to have.

The stop wire is black/yellow and runs from the kill switch and ignition switch to the power pack. When the wire is switched to ground with the ignition switch Kill switch or defective wire touching ground the PP stops sending spark.
 
PhilSch said:
If you want to work on outboards effectively a factory (OMC) service manual is a must. Do not bother with an aftermarket manual! You can PM me with your email address and I will send you a PDF copy of the CDI ignition troubleshooting guide which is nice to have.

The stop wire is black/yellow and runs from the kill switch and ignition switch to the power pack. When the wire is switched to ground with the ignition switch Kill switch or defective wire touching ground the PP stops sending spark.
Click to expand...

Pm sent, thank you.
 
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