testing a coil

[zoomzoom1970]

I have a 1999 100hp 4-stroke Yamaha . 2 bottom cylinders spark plugs are not burning clean and engine will bearly stay running. Already rebuilt carbs no change I am almost positive it is a coil pack it has 2 coil packs 1 for top 2 cylinders and 1 for bottom 2 cylinders. But before I spend the money I would like to know if there is a way to test them? Thanks!!!

 

[rodbolt]

Re: testing a coil

I am almost positive you still have carb issues.
what type of manometer did you use to set the shutters after reinstalling the carbs.
did you clean each carb fuel inlet filter?
top coil sparks 1 and 4 bottom coil sparks 2 and 3 on that motor. not the first person ever had to do it twice.
let the fuel lines dry over night,look inside them with a flashlight.
if you see any whitish or yellowish film toss the lines and install new ones all the way back to the tank.

 

[zoomzoom1970]

Re: testing a coil

What do you mean by carb inlet filter? I did not see anything like that. Carbs were totally taken apart put in a drum of carb cleaner with an agetator then sprayed 2+2 carb cleaner through all holes and air to make sure all passages were clear. Then I use small guage telephone wire and run it completely through all holes as to make sure there clear. Plus all new carb kits and filters all the way to fuel tank. Totally drained tank and the check valve on top of tank. But mabe Iam still missing something? This thing is driving me nuts! Only thing i can say the 2 bottom plugs are burning black and fouling. Also did a compression check all cylinders were even. Checked timing belt marks were where they belonged. any suggestions would be greatly appreciated! thanks!!!

 

[99yam40]

Re: testing a coil

you did not say how you adjusted the carbs after putting back on, did you use the manometers like the service manual says?

If you are wanting to test the ignition system, the service manual should give the ohms of the coils and how to test the input voltages to the coils, the inputs to the CDI, and the type of equipment needed to read the voltages

 

[rodbolt]

Re: testing a coil

did you also check the electrothermal valves for proper operation according to the service manual?