418A no spark

[prondzy 3,881]

Ok so im fixing a 418A for the neighbor.  It lost spark while mowing. I have swapped the coil and condenser with known good components still no spark. I jumpered power from B+ to the + of the coil and the tractor runs. I HAVE 12v at the keyswitch at key on. Am i right to assume that the low oil pressure switch failed and is killing this circuit?  And yes i checked the 9 pin with no signs of high resistance,  melting or the like. Any help from fellow onan owners would be greatly appreciated.  Especially if you have encountered this before.

[WHX?? 48,815]

Well I think you have eliminated the ignition components  so it almost has to be in the kill  circuits. Something up in the the board or a safety kill relay. Bypass the seat switch ? I would have to pull a wiring diagram to tell you more Mike. 

[953 nut 55,229]

1 hour ago, prondzy said:

lost spark while mowing.

I wouldlook for wiring at PTO or seat switch having a bad connection.

[Handy Don 12,227]

There are safety switches between the key and the "spark maker". When mowing, one side of the PTO switch and the seat switch carry the juice when in their proper positions and with clean solid connections. If the connections to one of these is loose or corroded, it'll kill the engine in a flash. Look at these first. 

 

[pfrederi 17,739]

I thought 418 A were a one year tractor with a Kohler Magnum 18 no coil no condenser no 9 pin....

[prondzy 3,881]

26 minutes ago, pfrederi said:

I thought 418 A were a one year tractor with a Kohler Magnum 18 no coil no condenser no 9 pin....

418a it has an onan in it original engine

[pfrederi 17,739]

Looking at the manuals section here for 418A there is only the one year with a Kohler.  You think WH stuck an Onan in at the end of the production run...if so it is a pretty unique tractor

[gwest_ca-(File Mod) 11,043]

Maybe a 518? Onan coils were only controlled by the pto switch and seat switch in Wheel Horse long frame models.

Oil pressure switch in 1988 controlled just the light.

 

[prondzy 3,881]

10 hours ago, gwest_ca said:

Maybe a 518? Onan coils were only controlled by the pto switch and seat switch in Wheel Horse long frame models.

Oil pressure switch in 1988 controlled just the light.

 

Thanks

[Handy Don 12,227]

@prondzy, can you please confirm the model/serial from the plate on the fender next to the seat and include photos? Differences between 400 and 500 could be important here.

Edited July 19, 2021 by Handy Don

[prondzy 3,881]

Ok my apologies it is a 518H. I work on so many of my neighbors tractors i mixed them up. 

Edited July 20, 2021 by prondzy

[Handy Don 12,227]

No apologies needed for being a good neighbor!

@gwest_ca has you fixed up with the manual and wiring diagrams. The 518 I worked on last year matched up with the diagrams nicely. I had one PTO microswitch that was flukey and I replaced it for about $5 from the Bay or the Jungle (can't remember which).

If your problem isn't the regulator, then my money is on a problem in the "running" circuit--switch failing, corroded connections, loose wire, PTO lever out of position, etc.