View Full Version : 79 johnson 100

05-22-2004, 05:06 PM
" OK here's the deal. I have 90lb compression in all 4 cylinders. I have spark through the spark plugs. While idleing I pull the plug wires 1 at a time, when I pull each of the wires (one at a time) each top one will almost kill the motor, the bottom 2 make no change like they're not firing but are wet with fuel. I can pull the plug and hold to a ground crank the motor and the plugs are sparking good (they're new). It will turn about 5000rpm on the lake but won't hardly idle because it seems to only be running on 2 cylinders. Any ideas??

Thanx in advance

Brian "

03-08-2006, 11:12 AM
"Hey Brian...Sounds like the two plugs are firing when removed and not under compression...The spark when cranking should be a good blue spark and just about 3/8" jump to ground..Don't jump to the plug, jump to the engine...Try this: With the engine running about 1500 RPM's in nuetral, pull one of the suspect wires and see if the engine slows down..then the other...If it does, they are firing at a higher speed...if not, then the coil pack is weak, or the charge coil under the flywheel is going bad..."