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entropy

Weak spark/ no spark 520hc

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km3h

Does this engine have points and condenser?

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entropy

No, it has the ignition trigger and stator. No points.

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entropy

I did disconnect the plug wire(at the spark plug end) and inserted a screwdriver in the end and held it near a ground source as I turned engine over and there was no spark.

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Geno

If you can leave the plug out, plug wire connected, and ground it with a jumper wire like Nick mentioned this will free your hands up for the next test.  You will need another jumper or wire.  Take that wire and ground it.  With the key on quickly touch the neg - terminal on the coil and see if you have spark.  You can do this several times.

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entropy

I am going to try this next, but before I do I want to thank all of you who have been helping me. A very kind thing to do for a complete stranger. Thank You!

What will this test determine?

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entropy

So I get spark when I quickly touch the negative terminal of coil, as per above instructions. I used jumper cables to make connections.

Edited by entropy

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entropy

Update, downloaded demystification manual. Went through testing via manual and coil tested within parameters. I went to test ignition module(which I replaced at a cost of $187) and it was out of spec. According to the manual the volts should fluctuate between 1/1.5 and 12 as you rotate the flywheel with the volt meter attached.

I am going to retest one more time, but this is very frustrating as the part is new and behind the flywheel. So I have to tear down the side of mower once again.

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entropy

So I put new coil on and repeated test. Volts start out at 12.5 and as I rotate crank they fall to 1.05 volt( this is what should happen according to guide). Problem is it should go back up to 12.5 volt again and it does not. So once again I am looking at the ignition module....... The new $$$$ part. Wanted to try test with new coil to see if results where similar before pulling flywheel. Results were different but still indicated ignition module.

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Martin

did you test the rotor at all?

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entropy

Just back from autozone, fried the 20A fuse. I am going to repeat tests with new fuse. Rotor? Not sure which part you are referring to, sorry.

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entropy

Ran ignition module test according to demystification guide and points to ignition module being bad. I rotate the crank and volts stay at 12.56. Should drop to 1/1.5 volts per each complete revolution of crank.

Going to go to the john Deere shop I bought the parts from to see if I can exchange it, my fear is they will not allow the exchange as it is an electrical item. I will now pull the flywheel and reinstall old ignition module and see if I get similar results

Edited by entropy

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Martin

the rotor (trigger ring) is the plastic ring that uses magnets to trigger the ignition module to fire. when you replaced the module, did you notice the plastic ring part on the crank that was almost touching the 'eye' of the module?

(from the first page in this thread.....)

 

post-4321-0-06041500-1411322870_thumb.pn

 

 

 

when you turn the crank, the magnets pass the sensor in the module and make it change from the 12 v down to 1 and back again.

Edited by Martin

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Martin

if the signal is at 12v and drops to 1 and doesn't go back again, what happens when you test it a second time? does it change voltage at all when you turn over the engine? how many times have you tested the voltage by revolutions. are you turning it by hand or cranking it?

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Geno

So I get spark when I quickly touch the negative terminal of coil, as per above instructions. I used jumper cables to make connections.

 

You became the "points".  You just found out the coil, plug wire and plug are all good.  Problem is with the guy telling the coil when to fire or the wiring between.

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entropy

What an education so far! So much so that I felt it necessary to become a contributing member to this forum. So I have now pulled off the flywheel, replaced the ignition module with the original and hooked up the volt meter(red) to (negative) coil post and hooked up black volt meter to (negative/ground) and spun the crank with key in the "run" position.

I now have the fluctuating current the guide calls for!!!

Next task is to check for spark, will let all know the results.

Once again thank you for all the help

Dave

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entropy

WOOOHOOO...... Tried to run with 1 spark plug out while testing for spark!

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entropy

Had to shut it down with key to stop her! Very satisfied right now, will have to button her back up and test run it

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entropy

Spoke too soon. So I got her all buttoned up and started her up. Ran fine, rolled her around yard for about 5 minutes and she started missing and then shut down. Pulled plug and checked for spark.....none. UGH!

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Geno

From what you've mentioned today sounds like you may have a wire touching somewhere it shouldn't.  :)

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entropy

When it quit I heard an electric "zap" up front. I pulled all the wires up front, cleaned the connections and replaced as needed, wrapped the wires in electric tape and reattached. Just finished riding it around for 10 minutes..... So far so good. Will reattach all components removed including hood tomorrow and try to cut lawn. Will update when I am done. Fingers crossed!

I hope I have fixed her, as I missed my tractor quite a bit.

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km3h

I hope everything is finally fixed. Sometimes it takes a lot of trying but usually perseverance will pay off in the end.

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entropy

As a side note, my tachometer quit working last year, after all this work when I ran it around yard for a few minutes the tach finally worked again. Guess the wiring is all jacked after 26 years of service.

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Martin

thats great you finally got it working. onan engine electrical can be tiresome and frustrating to work out whats wrong sometimes......

 

so, just to make sure here, you went through all this drama and aggravation pulling flywheel and other engine components, bought a new ignition module, removed and replaced various ignition components etc. etc. because of a loose wiring connection?

 

you've probably learned a lot more about your tractors engine and how the ignition system and associated components work so all of this wasn't a waste of time, i just think you could have avoided much of the frustration that you encountered by thoroughly checking out the electrical harness to begin with. its still not clear if you discovered any of the ignition components were to blame for your problems, thats one of the problems when replacing parts with out testing. maybe you could clear that up by testing anything you replaced ( you did the module already by replacing the new with old and it worked). the coil and other ignition components could be tested to see if they were the issue. As you found out, parts can only be reliably tested by fixing or bypassing bad electrical issues on a engine or tractor harness first. (that was the idea behind the jumper wire to the coil, bypassing the bad connection/problem area that hadn't been diagnosed yet)

 

hopefully, the problem is fixed now. 

Edited by Martin
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Geno

Here is my motto and has been for over 35 years of business, it's on the windows, pens, cards, everywhere!

 

 

post-13404-0-98675000-1411398564_thumb.j

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entropy

When I first started this process I was unable to get the demystification guide. That is when I started replacing parts as I had no guide. Once I got the demystification guide it was much easier to trouble shoot(side note, every one should have the demystification guide!).

The coil was bad, the plugs and wires were in need of replacement. The BIG $$$$$ item(ignition trigger/module) is in box original is on tractor.

Had her out today and ran for about 2 hrs, it quit once near the end. Sounded as if it lost spark. Waited about 1 minute as I looked it over. Restarted without a problem and continued to run until I put it away.

I think it is now fixed and yes I should have listened to the advice here on the forums before replacing parts willy nilly. My Father always believed in the KISS philosophy, Keep It Simple, Stupid(if a light does not work make sure it is plugged in first).

I did not follow this when I started my repairs. I now know quite a bit about this tractor so as you said Martin, it was not all in waste.

As a word of advice to any who read this thread who are having spark issues........ Get the demystification guide and CHECK ALL THOSE CONNECTIONS!!!! And support these forums by becoming a member.

Much gratitude to all those who offered advice!

Dave

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