Weak spark/ no spark 520hc

[entropy 104]

Hi All,

So I cleaned up my carb and it looked good. Tried running the WH and no go. Pulled the plugs and checked for spark and I would get VERY infrequent spark. I am thinking coil and or ignition module. I tried downloading the repair manual but I keep on getting a security warning and can not DL it. So does anyone have the part numbers for the coil and ignition module. Also how do I test those 2 components before replacing? Any other suggestions?

Thanks in advance,

Dave

[Ed Kennell 37,998]

Was it running   OK before you cleaned the carb?

[entropy 104]

Backstory....tractor would cut out every once in a while....like starving for gas or no spark. Then it became an issue once per each cut. Then it happened multiple times per cut, then it just stopped running. I figured it was the carb so I pulled off the top and cleaned, but the carb was not to bad looking. So once I put the carb back together I was able to start it, but it stalled out again. So I pulled the front plug and turned it over with the plug held close to a ground source and I got an intermittent spark/no spark scenario. The spark I would get seemed very weak and was infrequent.

So today I tore into it. Removed the flywheel and took off the ignition trigger that sits against the block directly under the crank. Priced it out at john Deere as the jd420 uses the same onan motor....price is $180.00!!!!! The coil is $137.00. I will replace this part and then try running it. All the wires and connections looked pretty good to me. The next step will be replacing the coil. After that it goes to shop if I can't get her running. I am hoping it is just electrical, not a valve issue.

[Martin 2,131]

there are cheaper ways to go about this. simple search on here will turn up sources for your parts at much cheaper prices, even a substitute coil can be used for around $40. the pickup can be bought for about $80 (genuine part). i don't have time right now but i can post up here a little later tonight your procedures for testing the module and coil. they are available in the demystification guide as well.....

 

 

i would test the individual parts first before buying new, unless you have unlimited funds and just want to replace everything......

 

you are not the first with these symptoms, there are different members on here with Onan ignition problems almost weekly. many of us have gone down this road before and most of the experiences are posted on here.

 

the best piece of advice i can give you right now is to search and read, there is a wealth of info on this forum......

[entropy 104]

Thanks for the input Martin. So far I am not put out with the price as I got the tractor for free and have run it thru 3 seasons. Let me correct that... Yes the price is steep but now that I have pulled this beast apart I might as well replace that part. Overall it is a great tractor and if I invest a little coin I am ok with it. I have read a bunch of threads r/t no spark and it seems the common problem is that part behind the flywheel. We shall see if it is and I will post up my results.....and yes I would like cheaper parts for sure, last time I checked I was not made out of money!

Thanks,

Dave

[Martin 2,131]

take a look here for parts prices

 

http://www.onanparts.com

[entropy 104]

Thanks again. I saw that price and wanted to buy but they are away till 9/12.... By then I would have to mount a multi pronged expedition to locate my yard boundaries. I wish I had more time, but I am pressed as of now and it is going to cost me. Thanks again for the help, I will post again tomorrow as the part should be in and I will reassemble and test......fingers crossed(I miss my mower!)

[Martin 2,131]

 

 

[Martin 2,131]

[Martin 2,131]

those last two are from the Toro Power Plus service manual (492-4006).

 

these ones are from the demystification manual. 

 

the coil section you need to look at is part number 71-6000.

 

 

 

[km3h 543]

What if you change these parts to the tune of about $300.00 and it is not your problem? In most cases, coils either work or they don't. Your problem could be as simple as a dirty connection or bad ignition switch. Not my tractor nor is it my money, but testing parts before buying new ones is the smart thing to do and with the help you can get on this forum, testing is a snap..

[entropy 104]

A good point km3h. At this point, after I have pulled the flywheel I am going to replace it. If that is not the problem then I have a backup part. Yes it is not the most frugal path but screw it now, lots of work to get behind flywheel. I hope I am right and this is the fix!!

[km3h 543]

A good point km3h. At this point, after I have pulled the flywheel I am going to replace it. If that is not the problem then I have a backup part. Yes it is not the most frugal path but screw it now, lots of work to get behind flywheel. I hope I am right and this is the fix!!

After you have spent all that money I hope you are right too for your sake. 

[Martin 2,131]

A good point km3h. At this point, after I have pulled the flywheel I am going to replace it. If that is not the problem then I have a backup part. Yes it is not the most frugal path but screw it now, lots of work to get behind flywheel. I hope I am right and this is the fix!!

 

so you replace the module, hook it back up together and it still doesn't spark. so now you think, well must be something else, hey? and you go on to looking at other components. 

 

at this point, are you calling the module you pulled out good and you now have a spare? 

 

what if the module and coil are bad? what if either one are still good?

 

you will never know if you don't test the parts, thats why i go to the trouble of finding the relevant parts of the manuals to help out. if you don't test them how do you know they are good or bad? 

 

just because you replace with new, doesn't mean the new parts are good, doesn't happen very often but new parts sometimes don't work for any particular reason. the service manuals are very simple to understand and with basic tools all these parts are able to be tested, good or bad.

 

also its rare, but if the rotor was bad, you didn't replace it, you got everything back together and then the ignition doesn't work, it will all have to come back off again.

 

please do yourself a favor and test the individual components you have, even though you bought a module, keep it on the shelf and use the old one if it tests good. check out this thread on testing, it adds to what i already provided you with above.....

 

[entropy 104]

Hey all,

So I finally have a day off to work on tractor. I went to hook up coil and forgot how it was wired! When I was working on tractor I took pics of everything so I would remember how it goes back together......of course I forgot to take pics of coil wires! There are two posts on coil ( negative is larger diameter) there are 4 wires to attach. 2 of the wires only fit the smaller positive post( red one from ignition pick up and black one from wiring harness). The 2 left over are the black from ignition pick up and one black that comes from a small barrel shaped piece( transistor?) mounted on bracket over motor near coil. My best guess is these two go on the negative post.

Only problem is I thought I remembered the skinny positive post having three wires and the negative only one.

Any input is appreciated, as I am stumped!

Edited September 10, 2014 by entropy

[Martin 2,131]

Condenser wire (the one from the barrel shaped thing!) goes to the positive. Only the black wire from the ignition module goes to the negative post on the coil. Don't ever connect the black from the module to the positive of the coil, you will damage the module.

Three wires to the positive, red from module, yellow 12 volts and black condenser wire.

One wire to the negative, the black from module.....

Sent from my iPhone using Tapatalk

[km3h 543]

Condenser wire (the one from the barrel shaped thing!) goes to the positive. Only the black wire from the ignition module goes to the negative post on the coil. Don't ever connect the black from the module to the positive of the coil, you will damage the module.

Three wires to the positive, red from module, yellow 12 volts and black condenser wire.

One wire to the negative, the black from module.....

Sent from my iPhone using Tapatalk

Exactly what I was about to say. You beat me to it.

Condenser wire (the one from the barrel shaped thing!) goes to the positive. Only the black wire from the ignition module goes to the negative post on the coil. Don't ever connect the black from the module to the positive of the coil, you will damage the module.

Three wires to the positive, red from module, yellow 12 volts and black condenser wire.

One wire to the negative, the black from module.....

Sent from my iPhone using Tapatalk

I was going to say that.

[entropy 104]

Ugh, no spark. Coil tested good, replaced plugs and spark plug wires as insurance. All fuses are intact. Disgusted right now, will have to reassess in the AM.

Thanks everyone for advice and help. Love my wheelhorse but this could be the end.....

[Geno 1,929]

Sorry if I missed it in the reading but is there 12 volts at the pos side of the coil with the key on and has it been checked with a test light also, not just a multi meter? 

[entropy 104]

Hi all, spent this very nice day tooling around with the 520hc. Updates...... new coil, new ignition trigger, new spark plug wires and spark plugs, cleaned 9 pin connector, replaced 20 and 30 amp fuses and fuse boxes. Still no spark.

Any suggestions?

[km3h 543]

I am going to ask the same question Gino asked. This is very important, so pay attention. Turn the ignition switch to the on position. Now using a test light, from negative side of battery to the positive side of the coil. Does it light and is the light bright? You can also use a volt meter from negative battery to positive side of the coil. Looking for 12 volts. Please run this test before you ask anymore questions.

[entropy 104]

With the ignition switch on I have 12.56 volts from neg battery terminal to positive coil terminal. With ignition off I have no volts.

[Geno 1,929]

Do you have an actual spark tester, other than yourself that is.   

[entropy 104]

Nope, just have the volt meter. I did take the wire off and inserted a screw driver in boot while I turned the motor over while holding it near grounded metal and there was no spark at all.

[km3h 543]

So now we have eliminated everything that precedes the coil. That is a major development.

Now if you have a jumper wire, which everyone should have by the way, I make them up with 12 gage wire and a pair of alligator clips in various lengths, take a spark plug or remove one from the engine and attach the jumper wire to the outside metal body of the plug and ground the other end to the engine or negative post of the battery. Put one of the coil wires on the plug. Hold the coil wire but not too close to where it attaches to the plug and try to start the engine. You should see the plug fire. Do not do this in bright sunlight as you may not see any spark.

A simpler way is to just pull one of the coil wires that go to a plug and hold it about half an inch above where it inserts into the coil. Try to start the engine. Spark should jump out of the coil post to the plug wire.

Another way to test this is to simply remove a wire from a plug. Insert a bolt into it and hold it near a metal ground. Spark should fly from the bolt to ground when you try to start it.

If you get spark then the coil and everything that it depends on is in good condition and you have a fuel or timing problem. All Automotive stores sell a neon tester to test spark. They are cheap and worth the investment. They even come with instructions.