Weak spark

[stoogr]

Can't get my JD 170 to start. Pulled a plug and turned it over and can't see any discernible spark. I can get the cap off the distributor, but can't do anything with it because I can't see it without pulling the motor (stupid design). I'm thinking the cheapest and easiest place to start is by replacing the coil. Any thoughts?

 

[thetool]

I never thought it was easiest and cheapest to just throw parts at something. If replacing your coil got you running, I would call it lucky......=). Try a mirror to see into your distributor guts?
Key on, see if you have power to your coil first. If you have a points system, you should have a resistor, so see if you have 12v in and like 9-10v out to your coil, with key in run position.
If you have a resistor, it should by-pass when you key to start, and you should get full 12v to your coil.
If you have points and power into your coil, check points, wear and gap. Check the wire coming off points to the condenser, and your coil ground wire.
And your plug wires, especiall the center wire cap-to-coil. Any of these things will keep spark from all plugs.
A few simple things to check before replacing your coil. Someone here probably knows what the primary coil resistance should be off the top of his head.
Good Luck.