Logo
FULL SITE MENU

Intermittent firingneed help

J

jmereid

New member
" I have a '72 evinrude 10

" I have a '72 evinrude 100 Hp. Motor runs rough. I have cleaned all grounds and have checked the coil, sensor, spark plug wires, distributer, etc. Can the amplifier cause an intermittent firing of the spark plugs? "
 
"J.... I've never run acro

"J.... I've never run across a Battery Capacitance Discharge system (which is what yours is called) having a intermitent ignition problem due to the powerpack. Those type packs were always either good or bad. They did have a habit of failing completely, staying that way for a hour or so, then coming back to life.... finally failing for good later on, but never being the cause of a intermitent spark problem.

I know that engine calls for Champion L77V spark plugs, but they have no heat range at all being surface gap plugs. I would suggest trying either Champion L77J4 or L77JC4 s/plugs and set the gap at .030. The difference between the two is the "C" which indicates a copper electrode which is supposed to last longer.

Check the continuity of the coil with an ohm meter from the rubber boot connector to ground, and from the rubber boot to the small coil wire that leads to the p/pack (I believe it's a blue wire). You should get a reading there of some king. If you do not get a reading, usually it is because the spring terminal inside the boot has lost contact with the inner wire of that coil lead. That in itself will cause a intermitent spark problem.

One other thing, and the flywheel will require removing to check it... If the "Reverse Cutout Spring" that rides the crankshaft right at the base of the timer base loses lubrication, the entire distributor cap and rotor will become incased with what looks like a "Black Powder" and that will cause all kinds of ignition interference. The cure is to clean everything, and if that reverse cutout spring is worn, replace it.... and lubricate it with what OMC calls Type D lubricant. I'd strongly suspect that you could get by with any high speed grease such as what's used in generators etc. If you can find the type D fine, but if not, use the high speed lube.

Note the flywheel must be torqued to 105 foot pounds. Make sure the flywheel key is installed with the straight edge vertical, not aligned with the c/s taper. Let us know what you find.

Joe
"
 
" I have the L77JC4's that

" I have the L77JC4's that you are talking about but when I installed them I did not check the gap. Just figured that they came properly gapped. I will pull them and check the gap. A friend had a new coil that we put on to see if that was the problem and that didn't cure it. I will check the coil wire as you suggested. I have had the flywheel off before to check the gap on the sensor. I did notice that there was some of this "black powder" that you mention but not a lot of it. What should I use to clean this stuff with? Electrical contact cleaner? When the flywheel was off, I had noticed the operation of this reverse cutoff spring. I didn't notice it being worn but I don't remember it being lubricated either. I will check all this tonight after I get off of work. I do appreciate you taking the time to help me out. This is my first boat and I am determined to get it running and enjoy some fishing.

Jaimie "
 
" Joe.....I have checked the g

" Joe.....I have checked the gap in the plugs, cleaned up under the distributor cap and lubed the reverse cutout spring. When I ohmed out the coil, I got 280 from spark side to ground. Got .7 from blue wire side to ground. Checked continuity on the coil wire to distributor cap and it checked good. Still have the intermittent fire.

Thinking about replacing the distributor cap, rotor, and spark plug wires. Getting a little frustrated. Any other suggestions?

Jaimie "
 
"Jaimie... Yea, they can be ve

"Jaimie... Yea, they can be very fustrating at times. There is something that I've ran across a couple times with that type ignition, a problem that showed up clearly at night but could be overlooked in broad daylight.

Remove the spark plugs. DO NOT connect anything to the spark plug leads. Have someone crank the engine over while you stand behind the engine looking at the ignition coil. If you can see any arcing between the coil and the metal coil yoke etc, the coil is failing, shorting out to ground, and requires replacing.

Also examine (while cranking the engine) the distributor cap at the spark plug wire areas to see if there's any arcing from thhe bottom portion of the plug wire area to ground. If so, unscrew the plug wire from the cap, insert some of that high speed lube in the hole, then screw the wire back in.... and recheck to see if that cured the arc at that area.

Joe
"
 
" Joe...I tried your suggestio

" Joe...I tried your suggestions. Saw no arcing. Rebuilt carbs. Still having intermittent firing. Put motor in barrel of water. Getting a lot of smoke due to miss in firing. Also, will stall when put in gear. Going to have the coil tested. Not sure what else to check. Is the rectifier part of the power pack on this year model? Could a bad rectifier cause this? Decided to wait on replacing distributer cap after finding out they want over $100 dollars for one.

Jaimie "
 
"Jaimie.... Your engine should

"Jaimie.... Your engine should not have the feature that I speak of here, but just in case! Check on the starboard (right) side of that powerhead to see if there's a plastic cup like component that has a rubber diaphram cover. If so, that diaphram has a metal cap attached to the inside of it. If that diaphram has a pinhole in it, a crack, a split etc of any kind, it may interfere with the ignition. I didn't mention this before due to the fact that your engine wasn't equipped with it, but who knows for sure.

I'll take a look at what I have left in stock to see if I may have a distributor cap and rotor. The rectifier wouldn't have anything to do with the ignition.

Joe
"
 
You must log in or register to reply here.
Back
Top