Craftsman / Briggs 18HP Running on 1 cylinder

[Scooby074]

I installed the "new" coil.. RH side is totally dead

I didnt have time to do much troubleshooting, but i tried unplugging the coil kill wire.. made no difference.

This coil came new in new style briggs box, but it looked like it was very slightly used. THe parts guy assured me it was new and just got bumped around in the box. I dont know.... This was exactly what i wanted to avoid when buying a new coil instead of a used one. I dont know if the "new" one was defective in the box or if i have some other issue.

Is there anything im missing on that engine that could cause my problem?????

It has magnetron ignition, the only parts to it are the coil and the flywheel, as far as i know. Is there any other components to the ignition that could be causing me spark only on the RH side and not the Left?

 

[heehaw]

don't know if yours is this way or not: but i had a sears lawn tractor with an onan engine: both cylinders fired at the same time, so the plug wires could be reversed with no problem: when one cyl was on the power stroke, the other was on the exhaust, but both plugs fired at the same time: if yours does the same, it would tell you if the coil is bad or not..
heehaw

 

[Scooby074]

HeeHaw: Yeah this is a wasted spark engine. Same as yours.

Ive swapped the plugs left to right (ie: put a known good plug on the "dead" side) and still no joy.However the formally dead plug magically came back to life when put on the good side.

The plug leads are only long enough to go from the coil to the plug where they're supposed to go. So i cant hook the coil up to the "wrong" clyinders for testing.

Good idea though. Im totally lost on this one,. It doesnt make sense.

 

[carpenter383]

If you have good compression it's not the valves/seat, head gasket, piston/rings. It wouldn't hurt to adjust the intake valve in question, but I can't see that being what's causing your problem....This may sound obvious, but does your coil say "this side out" on one side? Is that side out? The coil has a positive and negative just like any other coil. It can still fire if reversed, just not very hot.
Good luck!

 

[heehaw]

grab a couple old plug wires off of something and extend the ones on the coil to test it..
heehaw

 

[Scooby074]

If you have good compression it's not the valves/seat, head gasket, piston/rings. It wouldn't hurt to adjust the intake valve in question, but I can't see that being what's causing your problem....This may sound obvious, but does your coil say "this side out" on one side? Is that side out? The coil has a positive and negative just like any other coil. It can still fire if reversed, just not very hot.
Good luck!

Yeah, its labeled, and installed correct. Checked that like 3 times. I was thinking that too.

I talked to a mechanic today at the JD dealer. He said what ive been saying, that its sounds like it has to be the coil, but the chances of 3 coils being bad is extremely thin.

He also said that there is a remote possibility that the engine is rotating backwards. He said its possible for these engines to run either way. Im thinking that this is my last hope lol. Im going to feel pretty stupid if thats the problem.

THere really isnt any way to adjust the valves, besides pulling the head and relapping to lower the valve in the seat.. If that doesnt work youll need a new valve. Im going to fix the spark issue before digging further into the valve problems.

Those new john deer 300 series in the showroom sure looked purdy


Heehaw: im going to try that tomorrow if i get time.

 

[jhwentworth]

What type of spark tester are you using? Can you connect the tester in series with the the spark plug while the engine is running? If you can do this, and the tester shows a strong spark, then you can pretty much forget any coil problems. Have you checked the magneto key? I've seen some strange problems happen when the key was sheared and the timing got altered. What type of intake manifold tube do you have? Early versions of this motor had a multi-segment tube that would leak and cause poor combustion in a cylinder. Later versions have a solid tube.

I would agree with previous posters that 120psi in both cylinders should rule out valve issues.

After running the engine for a while, what does the spark plug look like in the bad cylinder? Gas soaked? Oil soaked? Dry?

Af far as an obstruction blocking the exhaust: try removing both spark plugs then blow some compressed air up the muffler output with the exhaust valve open (have the compressed air blowing into the muffler while manually turning the motor over. When the exhaust valve opens the air should be felt at the spark plug hole.)

 

[swines]

Check the plug wire on the bad cylinder. A bad plug wire will give intermittent spark if the wire core is broken or cracked.

 

[Scooby074]

Thanks for the replys. I was having some computer problems so im a little behind.

Ive also been busy doing some landscaping (probably will be all weekend) and havent had the time to fool with the mower but i can answer some questions

jhwentworth: Im using a lisle tester like this Amazon.com: Thexton 404 Adjustable Ignition Spark Tester: Automotive

So i cant connect in series,

I havent pulled the flywheel yet to check the key, but i will when i get back at it.

Intake is a solid one piece cast/ it connects both cylinders.

After running the plug is dry and does not smell like gas, but is very carboned up. Both plugs are carboned, with the runing cyl having the most.

Ill try blowing up the exhaust after i get the spark thing figured,. Right now, thats the most important thing. then ill troubleshoot any flooding issues if they remain.


Swines: the plug wires to the dead side are brand new. They came with the coil. They are perminantly attached to the coil so i cannot remove them and swap sides.

THe coil wires arent even in their "hole" through the heat shield. Theyre just laying loose on the RH cylinder, so i know that theyre not being pinched.

 

[carpenter383]

It might be better to blow through the cylinder and out the exhaust instead of throught the exhaust and into the cylinder. You don't wanna blow a bunch of junk into the cylinder.