18hp opposed twin flooding- spark issue?

[Xbenx927]

I’ll try and keep this short

Rebuilt motor last year in spring. Ran great this spring. Pulled out of mower and had mouse nest in flywheel area. Used mower for a 45mins. Ran a hair rough but still ran, just slightly off. After 45 mins it started running quite rough then died. Started up then died. After twice it won’t start at all

cleaned plugs and fired right up then immediately dies. Cleaned plugs and fouled again-gas fouled
Took plug off wire... fires up and runs good if I send spark from open wire to plug.... soon as I connect plug or move to far it dies. This is same on both plugs. I installed new coil last year
Choke doesn’t seem to play a part in running and throttle doesn’t seem to play a part. I rebuilt carb a few years ago

im leaning towards some mouse gunk on top of case/under flywheel/around coil but would like to hear some options before I take the time to undue everything again. I’m open to ideas

thanks in advance

 

[bertsmobile1]

Check the kill wire to the coil for chewed through insulation that is shorting out against the engine.
The kill wire should be open ( neither power nor ground ) and goes to ground to stop the sparks
So if the insulation is breached and the bare wire can touch the engine, no spark.
Double ended coils have a + spark at one end and a - spark at the other and if the insulation is compromised anywhere you will get bad / no sparking

 

[Scrubcadet10]

Clean the mouse crap off the engine... check to be sure fluffy didnt chew threw the coil kill wire letting it ground out the coil producing no spark

 

[wrldtvlr]

Took plug off wire... fires up and runs good if I send spark from open wire to plug.... soon as I connect plug or move to far it dies. This is same on both plugs. I installed new coil last year
Choke doesn’t seem to play a part in running and throttle doesn’t seem to play a part. I rebuilt carb a few years ago

Going back to my school shop days, back when cars had carbs and could be tuned (!!!). If I recall correctly, pulling the plug wire off a bit from the plug is equivalent to retarding the spark, something you have to do if the mixture is too rich. The clue is in your first post - gas fouled. I'd check the float or choke control again before tearing the engine apart.

 

[Hammermechanicman]

Pulling the plug wire away slightly doesn't retard the timing (speed of light thing) It acts as a booster gap and increases the amount of energy it takes to junp both gaps. Back in the day of cars with point ignitions one of the snake oil products in the JC Whitney catalog was the Spark Intensfier that made the car run better with fouled plugs. It was just a booster gap you plugged into the distributor cap. Works great till you try to start the car on a day below freezing and the battery is a little low and the ignition system doesn't have the energy to jump both gaps. Your plugs are probably fouled and the ignition system is fine. Figure out why the plugs are fouling, oil or gas then install NEW plugs.

 

[wrldtvlr]

Pulling the plug wire away slightly doesn't retard the timing (speed of light thing) It acts as a booster gap and increases the amount of energy it takes to junp both gaps. Back in the day of cars with point ignitions one of the snake oil products in the JC Whitney catalog was the Spark Intensfier that made the car run better with fouled plugs. It was just a booster gap you plugged into the distributor cap. Works great till you try to start the car on a day below freezing and the battery is a little low and the ignition system doesn't have the energy to jump both gaps. Your plugs are probably fouled and the ignition system is fine. Figure out why the plugs are fouling, oil or gas then install NEW plugs.

Thank you for refreshing some worn out brain cells! JC Whitney. Wow. That's a name I've not heard in decades. Used to pour over that catalog. Plastic VW body parts! Cheap AM radios also. Custom fit? Nah, just use a couple of L brackets under the metal dash...

 

[Xbenx927]

Thanx guys for all the responses.
I figured either mice chewed something or part of their nest got wrapped around and did some damage. I just couldn’t put my finger on it to pull the trigger on tearing into it more. I was looking for some reassurance and sounds like most are on the same page. I’m sure it will be an “ah ha” moment when I get in there

I’ll let you guys know what I find. Thanx again everyone!

 

[Xbenx927]

I thought about this as well but being I had no issue lately and it was acting weird I figure odds are it’s something new (something caused this) before I go searching in a random area. If the mouse nest wasn’t there I would likely start at the carb since that’s logical with having spark. If I had not tested spark the way I did and didn’t see the nest it could be a wild hunt. Amazing how fast those little buggers set up shop. Gone for 2 months and I’ve killed 15 in 4 days in the shed. Shed looks like a anti mouse military base now lol

Going back to my school shop days, back when cars had carbs and could be tuned (!!!). If I recall correctly, pulling the plug wire off a bit from the plug is equivalent to retarding the spark, something you have to do if the mixture is too rich. The clue is in your first post - gas fouled. I'd check the float or choke control again before tearing the engine apart.

 

[Scrubcadet10]

Barn cat time!

 

[bertsmobile1]

Pulling the plug wire away slightly doesn't retard the timing (speed of light thing) It acts as a booster gap and increases the amount of energy it takes to junp both gaps. Back in the day of cars with point ignitions one of the snake oil products in the JC Whitney catalog was the Spark Intensfier that made the car run better with fouled plugs. It was just a booster gap you plugged into the distributor cap. Works great till you try to start the car on a day below freezing and the battery is a little low and the ignition system doesn't have the energy to jump both gaps. Your plugs are probably fouled and the ignition system is fine. Figure out why the plugs are fouling, oil or gas then install NEW plugs.

Actually Hammer you are not quite correct.
Increasing the gap does retard the spark.
The potential between the electrodes does not go from 0V to 30,000V instantly but rather starts at 0V then rised to 30,000V then drops back to 0V again in a sine wave form.
Now the time is very very short, but it is a typical wave.
The rest is correct, the spark intensifiers ( which have been around for 100 years ) just put a resistance before the spark plug that is greater than the resistance of the air gap of the plug so the rise from 0V to 25,000V happens at the intensifier and the first potential the plug sees is the 25,000V which was often enough to make a fouled plug spark rather than track down the fouled electrode.
The std fix for a fouled plug was to pull the cap on a running engine about 1/4" to 1/2" off the plug and hold it there till the cylinder started to work with the cap on properly.

The "advance" on a lot of EI chips is just that, a bank of resistors that go in & out of circuit in order to reduce the amount of retardation of the spark as you can not advance it electronically.
The old Atom Industries EI chips did exactly that.
The different chips had different internal resistance to change the amount of retarding of the trigger signal.