93 520 h no spark

[champ97 0]

Hey guys new to this forum,looks like a great place for info. tractor has 20hp onan runs great when running,problem started with intermitent spark,weak spark. Downloaded demistication guide for wiring , have indivdually bypassed safty switches to eliminate those, ran hot wire to hot side of coil still no spark. At this point thinking it is coil or trigger, is there a testing procedure that can be done with multimeter, dont want to just start replacing parts. gets expensive thanks..

[Save Old Iron 1,564]

The trigger for the coil is an electronic unit on the crankshaft. A transistorized switch is triggered by a magnetic ring on the crankshaft. The transistor switch will ground the coil (-) terminal when the magnet passes the trigger.

I'll have to look up the exact procedure, but something like this

ignition switch in run - engine off

voltmeter lead on the coil(-)

other meter lead on ground

slowly rotate the crankshaft by hand while observing the meter voltage

voltage will go from battery voltage to within 1 volt of ground when magnet passes the trigger module

the trigger voltage changing is functionally equivalent to the points opening and closing on a points based ignition.

I believe the exact procedure is in the Onan service manual. Someone here may have it at their fingertips at this hour. I can post the procedure later today.

Good luck and welcome to the forum.

[Save Old Iron 1,564]

Here it is

start with section 8-1 in the manual

[champ97 0]

Thanks for the quick reply,did trigger check first put meter on o-20 volts 13.25 at battery,checked across +/- polls on top of coil,got same voltage, did not change while rotating flywheel,at this point thought trigger,then proceded to check to coil got very erratic low readings on ohmmeter. at this point removed coil, coil had obvios signs of getting very hot top melted,bottom melted, there looked like a ground strap on bottom that was broken and very brittle pretty sure its the coil. ordered new updated coil today $116 bucks plus tax.do you think the bad ground strap caused problem, would a shorted coil cause reading i got when i checked trigger.thanks

[Hallas 0]

sort of going through the same problem with an '89 520. I get normal ohm readings on the primary side, but nothing at all on the secondary. I still have to check the computer module but i t hink the coil is dead anyways.

The coil from toro is outrageous $$$, as well as PartsTree. Are there any aftermarket coils available from other suppliers?

[champ97 0]

Dont know about aftermarket,took onan part number off coil and looked up online, had to order at dealer but 50 bucks cheaper for the updated onan coil than the toro part..

[Hallas 0]

would something like this work?

http://onanparts.com/index.php?main_page=product_info&cPath=1_16&products_id=95

[champ97 0]

I ordered the 541-0522 retrofit kit,not sure if one in picture will work. part # on stock coil was 166-0761

[Hallas 0]

did that coil work out for you?

[champ97 0]

yes it did