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sean2012

wheelhorse 520h onan engine no spark

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I have a wheel horse 520h with the onan engine model p220g-i/109550 and for some reason it has no spark

it has a new coil a new ignition module and condensor i have did all the tests for checking the module the voltage does not pulsate when its turning over the coil has 12 volts going to both negative and positive terminals when we had the module off of the tractor it had 12 volts the minute it is stuck onto the case it looses all power my rotor is in good shape and not broken does anyone have any suggestions on how to fix this thing so it will run again thanks sean

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try bypassing the factory wiring completly. you will have to get it to turn over and then just take a seporate wire for a ground to the frame to keep it running when you take the power from the starter. then put the 12 volts to the positive side of the coil. if it works there you will have a problem with the tractor harness. good luck

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havent got it going yet gotta wait till i get more money for parts does anyone have any cheap carbs forsale for the onan engine i ended up breaking the pickup tube in the carb

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did you get the spark back and the (-) side of the coil pulsing ?

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Make certain the ignition is wired as seen below. Note the condenser is connected to the (+) terminal of the coil.

015afc6e.gif

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Did you check coil primary resistance (with coil out of tractor or with power off to coil.

onancoilprimarymeasohms_zps1f4e2d7f.gif

It is possible if the coil primary is open, there will be 12 volts constantly present at both the (+) coil terminal and the (-) terminal,

The (-) terminal gets the 12 volts from the output of the trigger module. The Black lead to the coil (-) terminal IS NOT THE GROUND FROM THE MODULE - IT IS THE OUTPUT OF THE MODULE. THE METAL TAB ON THE MODULE IS THE GROUND CONNECTION.

The ignition modules I have bench tested all powered up with 12 volts on the BLACK wire from the module. When one of the magnets in the trigger ring passes the module "nose", the module output (Black lead) stays positive. When the 2nd magnet in the trigger ring passes the module "nose", the module output grounds out the (-) terminal of the coil and the process repeats.

1f225173.jpg

FYI - this sheet of magnetic sensing mylar shows the magnet fields in the trigger ring

0962ed48.jpg

Let me know if you have performed the primary coil resistance check and we can go from there.

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Hi Save old iron, my 520h was running ok , put it away next time I came to use it it backfired a couple of times then completely dead no spark. I was very impressed by your reply, I followed what you said to check the coil. I got 3.6 ohm on the primary and 17.6k ohm on the secondary. But I too don't have a spark, I have also hot wired to the positive side of the coil still no luck, but I had 12v there anyway.

I checked and had 12v on the - side of the coil. I also checked the voltage coming out of the module when I turned the engine it read a constant .6 volts.

I might had made things worse by doing this..... Before I read your post. I disconnected the ign module so the coil and capacitor was stand alone, I put 12 v to the positive side and took the negative side to the battery negative, as I saw it the coil should charge then when I lifted off the negative lead I thought it should spark but it won't, could the capacitor be faulty? I'm wondering how both the ign module and the coil could both go down together. I've NOT put a positive to the neg side of the module but wondering if the coil has failed that it's put 12v to the neg side

It's exasperating!!! I could order both coil and ign module and still not have a spark like Sean above!

Any help would be appreciated. I'm in the uk not many wheel horses over here. Engine transmission is strong so I'd like to fix her up.

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I am not familiar with your engine, do you have points?  The condensor could be bad.

Have you tried testing the resistance of the plug wires?  You should be around 12,600 - 15,400 ohms resistance from the coil side to the plug side.

This is not such a likely issue given that it was running and suddenly stopped but worth testing.

I have an old Serf that did the same thing last fall but I have not looked at it yet.

 

Good luck.

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No it's got tci ignition module , no spark at the coil so not the plug leads.

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put your meter on the negative side of the battery and the other on the negative side of the coil. spin the motor over by hand and the voltage should go from battery voltage 12. what ever down to around 1 volt and then back up. if you check the onan manual it will walk you through this and all electronic check out procedures. good luck

 

 

 

eric j   

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Backfiring almost sounds like the timing is off, my onan did the same thing. turned out in my case I didn't torque the flywheel enough and it sheered the key causing backfiring then not starting at all.

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Hi Eric I tried that with the ign module connected it was a constant 0.89 v , it didn't oscillate. So I do suspect the module. However I don't understand why if I take the module out of the equation, I can't get the coil to spark by mimicking the build up of voltage and then the collapse of voltage in the primary circuit which as I understand it should give a spark.

Moto I can turn the engine with the nut on the fan. But I'm not getting any spark as opposed to a spark at wrong time.

Frustrating

Maybe the capacitor is down. Would that stop the spark?

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the onan manual tells you haw to check the coil, i'm not sure about the condenser might be in the manual. the condenser does go on the + terminal of the coil. if you have 12 volts going to the coil and the wire is ok then you should get 12 volts back to the - side of the coil if not i would say replace the ignition module. like I've said numerous times before check the onan engine manual good luck

 

 

 

eric j 

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No the capacitor will not prevent spark. I bought a 520H that didn't have the capacitor installed and it ran fine, not really sure what the role of the capacitor is in these engines.

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No the capacitor will not prevent spark. I bought a 520H that didn't have the capacitor installed and it ran fine, not really sure what the role of the capacitor is in these engines.

The capacitor serves one of the same functions as in a coil based system. Between the coil in the ignition coil and the external capacitor, a little oscillator circuit is setup. The capacitor causes current to wash back and forth thru the coil for a few fractions of a second. This action will "extend" the time a spark exists across the spark plug gap. Not so much a "multispark" but an "extended spark".

Edited by Save Old Iron
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Hi Eric I have followed the manual, by all accounts the coil is in specification. However I'm worried if I just bought a new module if the coil is faulty then it might burn out the new ign module , what I'm blowed I can't figure out is why I can't get it to spark. I mean all the tci module is allow the current to build to 12 v and then break the circuit and it sparks, unless I'm missing something then surely I can simulate that by feeding 12v to the positive side and neg to the neg on the battery then breaking the circuit surely coil should spark if ok!

Guess I'm faced with getting both coil and module ..... Why would both fail together!!! What do you reckon Save old iron? Thanks you guys for your help I'm running out if ideas.

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 What do you reckon Save old iron?

follow eric j's advice on checking for the 12 to 1 volt transistions while turning the flywheel.

 

the ignition module in the 520 acts like the points in a Kolher setup.

 

as far as the capacitor function .... some vintage info on how a capacitor and inductor (ignition coil) act to extend the spark at the plug - hint - the rubber bands in the demo are the ignition coil winding and the condenser in your tractor

 

Edited by Save Old Iron

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If the tractor has been stored outdoors over the winter, it's not unusual to lose the ignition coil.  I have lost one on my tractor to this.  The very fine wire the secondary is wound with breaks easily if moisture works it's way into the coil and then you get thaw/freeze cycles.  You can test the coil off the tractor.  Connect a usable spark plug to the secondary and ground.  Hook a 12V battery across the primary of the ignition coil with clip leads.  Tap the clip leads to intermittently make and break the circuit.  If you get spark, the ignition coil is good.  No spark, the coil is bad.  Do not operate the coil without a plug connected.  That can cause break down of the coil's insulation internally.

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