something for all you johnson experts

[rmpenton]

I have a 77 johnson 115 that is only running on three cylinders.i have looked at every possible cause and found nothing.first it had a blown head gasket on # 1 cylinder.so i fixed that.rebuilt carbs.and it still only runs on 3 cylinders at idle and intermediate for sure.possibly at high rpms also.its the # 2 cylinder that is dead.i switched plugs,switched coils with the number 4 cylinder and the # 2 is still dead.pulled carbs again and checked again and everything looks good.no reeds are broken. if i pull the plug wire off when idling there is no noticable drop in rpms the coil sparks good.when i put the spark plug wire back on it idles up for a second literally,then drops back out.when the heads were pulled everything looked good no scars in any of the cylinders.if anyone has any sugggestions i am willing to try anything.if you need more info then ask im sure i left something out.thanks ryan penton

 

[22WRF]

Re: something for all you johnson experts

Just a suggestion have you checked the plug wire on #2.<br />Insulator on the plug cracked?<br />Tried to firing up it in dark is see if spark from # is jumping to ground?

 

[rmpenton]

Re: something for all you johnson experts

i switched coils with # 4 and got the same thing so it couldnt be that or the problem wouldve moved with the coil

 

[Joe Reeves]

Re: something for all you johnson experts

rmpenton..... You say: "if i pull the plug wire off when idling there is no noticable drop in rpms the coil sparks good.when i put the spark plug wire back on it idles up for a second literally,then drops back out".<br /><br />I assume that it is indeed #2 cylinder that you're having a problem with. It got somewhat confusing. At any rate......<br /><br />That would indicate that very little fuel is being drawn into #2 cylinder, not enough to be creating a combustible power stroke with the plug firing on every stroke. However, when you remove the plug wire, that small amount of fuel is not being ignighted and is building up in volume with each stroke. Then when you put the plug wire back on, that volume of fuel ignites for just that short blast... then the cycle continues.<br /><br />This would lead me to believe that something is being overlooked in the top carburetor of the engine, possibly the fixed brass high and/or slow speed jets?<br /><br />Compression on that engine should be in the 100+ psi range and even on all cylinders, and the spark (with the plugs out) should jump a 7/16" gap with a strong blue flame on all cylinders. Are these two items within specs?

 

[rmpenton]

Re: something for all you johnson experts

i havent checked the compression lately but the last check was 120 in the top cylinders and 125 in the bottom.all my jets look good and clean and after running it there is fuel on the plug,its not dry like if it was leaning out.i tried diffrent jets and on change.could the spark be good out of the motor but when i put the plug back in it dies?

 

[rmpenton]

Re: something for all you johnson experts

does anyone know what size jets are suppose to be in there?

 

[clanton]

Re: something for all you johnson experts

If this engine has two power packs, disconnect the black/yellow between the packs and try it.

 

[rmpenton]

Re: something for all you johnson experts

it only has one powerpack

 

[petryshyn]

Re: something for all you johnson experts

rmpenton<br />When it comes to electronics, anything is possible. I would switch number #1 and #2 trigger inputs, and #1 and #2 output to coil primarys. This will see if the misfire problem transfers to #1. If it does, its an ignition problem, and gives you a direction for troubleshooting. If it doesn't change, look to fuel or engine mechanical...

 

[rmpenton]

Re: something for all you johnson experts

could the gaskets behind the reeds be getting soft and make it do this?