I guess you have a 10684 or 10683 'Insight'? The first thing to check is the mulch plate or bag installation. The heavy wire extension must be all the way down in the RH retaining slot on top of the discharge box. There should be no debris in the channel under the frame. Make sure the piece is snugged all the way down, because there is a magnetic switch under it which cuts off the ignition to prevent starting/running without anything covering the discharge port.
If that's not it, look at the switch wire connection at the engine brake (the part that moves when you operate the engine/blade control bail). If that is a good, tight connection with no corrosion, it's probably okay.
Now you'll have to remove the tank shroud and steel air shroud to get to the coil and flywheel. It has been reported that the magnet on the flywheel on a very few units has come loose, killing any magneto effect. Plus, you'll need to do this anyway to replace the CD pack (coil).

"I guess you have a 10684 or 10683 Insight'"?...No he probably has a 10272, 10367, 10356,7 or 8. These are the old-style staggered-wheel steel decks so there is no magnetic switch. Since coils can't be tested I guess you just buy one and take your chances. Maybe he could try the oven bake and if this fixes the coil, temporarily, he'll know it is the problem.

evdpgh is right, it's the steel deck, staggered wheel model with the Tecumseh 4 cycle engine.

I happen to have the 10367 which is power-propelled and has the sense-a-speed drive system. In my opinion it is the best mower I have owned and I dread the day it quits. I wouldn't hesitate to try a new coil. You've got remember that it's 8 years old and things are going to start breaking.

the kill cable may have stretched to the point it no longer has enough travel to make the switch open . check for proper travel on the kill switch. dont see techumche coils go bad often but they can

ha ha cut them two wires .. it starts on the first pull.. the two going to magnetic switch .. grass evacuation port