coil question

[powerslide]

I have a 78 115 johnson

I checked my coils w/ the screw driver in the plug and jumped it to the spark plug. 3of4 would jump 1/2in 2 maybe a little further. The 4th would only jump about a 1/4in.

My motor runs on the water but is fairly finicky on start up and seems to idle too low. I have the idle screw all the way in.

Could my 4th coil that will only jump 1/4in be the cause of my miss?

Its been a year since the carbs were rebuilt. I dont think the carbs needing rebuilt would cause the miss would it?

 

[F_R]

Re: coil question

That 4th coil is highly suspect, to say the least. You should arc the screwdriver to the corner of a head bolt instead of to the spark plug. That will eliminate the spark plug from the test.

Check the secondary resistance of that suspect coil with an ohmmeter (multimeter). You probably will find it is unusually high. Or it could be just the plug boot or wire. The resistance check will pick up either one.

 

[emdsapmgr]

Re: coil question

All the coils on this engine are the same. Switch two of them and see if the misfire problem moves.

 

[powerslide]

Re: coil question

I started pulling wires one at a time. When i pulled the starboard side wires the motor died instantly. The top on the port side made a little difference and it start to stumble and would of eventually died if i had not placed the boot back on. I got to the bottom on the port side and it didnt do anything when removed.

So i shut it off and put a screw driver in the boot and started it again. Went over and held it up to the spark plug and it would fire about 3-4times and then wouldnt fire for 3-4seconds...

Is the coil bad or another part in my system?

I should of done the same to the top cylinder on the port side but i didnt think about it at the time.

 

[emdsapmgr]

Re: coil question

Sounds like you may have a bad power pack. Your engine has two-both identical, one for each head. Sounds like the starboard power pack is the good one. You can swap those two packs and see if the problems move to the other head. If so, replace the bad power pack.