Need JD 420 Garden tractor help:

David,

Testing the electronic ignition on a Performer series Onan engine is detailed in the TM1590 Service Manual.

Here are a few illustrations and steps from that manual that should help...

ignition timing test from TM1590.pdf (28.2 k)

Often these modules start to fail only at elevated temperatures, so your engine may fire up again when it is cold, and the above tests might check out OK when cold...so re-measure shortly after it quits if it does so again when hot.

Chuck

Your coil is very likely still good...there is some discrepancy in the Deere manual against the factory manual:

Onan manual illustration:


TM1590 version:


You quoted the Onan manual which you mentioned you had in your earlier post, and in general I believe it to be the more authoritative source. My experience is that the range could be a bit low for modern digital meters that use a much smaller sense current when measuring resistance than the analog Simpson meter illustrated, however. Your measurement is close enough to look for another root cause...

Of course, if the coil acts differently when the engine is up to temperature that is another matter. Elevated engine temperatures can also effect the condenser, as well as the ignition module which I described in my earlier post.

Have you done the hand rotation of the engine with the meter on the switched side of the coil to determine that the ignition module is working at room temperature? Has the tractor started and run now that it has cooled down from when it "quit"?

Chuck

David,

there is another section on the earlier B-series coils with different ranges:


...Also, be cautious of applying voltage where it does not belong when testing your ignition system:


From your earlier post about some spitting back through the carburetor and the noticeable vapor -- have you checked your valve clearances? Maybe you have a loose seat (that should have shown up on the compression test...is that something you have done yet?)

Chuck

Thank YOU, Boomer!!

...and have a GREAT 4th.

Chuck