1996 520H starting/electrical problem

[Skreegy 0]

Hi All,
My first post here although I have read the forum with interest for a while.

I hope some kind soul will be able to offer advice on the following :-

Onan engine...P220G-I/10955G.      While mowing a couple of days ago tractor just cut out. Left it for an hour and it restarted but stopped again after 20 seconds. Now will not start at all. Checked fuel - it's getting to the carb fine. Fitted new plugs 3 weeks ago. Removed plugs and turned engine over..no spark. However, as I turn the ignition key to  off , there is one spark at the plug. Hopefully someone will be able to point me in the right direction.

Thanks for reading this.....

[gwest_ca-(File Mod) 11,393]

I don't know anything about this ignition system but the spark plugs fire each time the power to the ignition coil primary winding is interrupted. With a system using points and condenser this happens when the points open. With the electronic ignition this is done by the trigger module. I will guess you are getting the one spark because you shut the ignition off and that interrupted the power to the coil primary one time. 

I believe some Onans have a condenser on the coil (+) side of the coil primary. I don't know what happens if it fails.

The procedure for checking the ignition is in the Onan service manual
http://www.wheelhorseforum.com/files/file/6-engine-onan-p216-p218-p220-p240-sm-492-4006pdf/

Garry
 

Edited August 8, 2015 by gwest_ca

[Kurt-NEPA 755]

Welcome to Red Square.

The 520H has a complicated electrical system, at least for a tractor.  Before you go to far, I would check that you are getting power to the coil.  When you turn on the ignition, 12V goes through the seat switch and then fires the Kill relay to energize.  The Kill relay is located below the battery and behind the engine.  There are three relays there.  The other two fire the starter.

A quick easy check is to get someone to sit on the seat.  Then put your hand on the relays. Turn on the ignition switch (do not start). You should feel the relay click on.  If yes, I would get a test light or meter and check for 12V at the coil.  Its always best to check these safety circuits first as they have a reputation for problems.

Keep us posted

520H Spark Circuit.jpg

520H Spark Circuit in Run.jpg

Edited August 8, 2015 by Kurt-NEPA
Update Image

[boomers_influence 106]

skreegy
it sounds like an ignition switch gone bad.
easy to check
turn key to run position,
you should have 12 + volts at the + side of the coil.
if this is so,
turn key to start position,
you should also have 12+ volts when cranking.
thank you boomer ( the used onan engine parts guy, also NOS and new )

[Skreegy 0]

Thanks very much for the responses and your time. Wiring diags and advice much appreciated. Couple of questions if I may :-

I bought this Toro used and the previous owner has removed seat switch and just connected it together to bypass seat safety. It ran fine like this for me for the 3 years I have had it...I know its not the safe way but would this cause a electrical circuit problem?

I have been having trouble with the ignition switch...sometimes it would do 'nothing' for a number of tries and then it would activate. Is there a simple way to 'hotwire' this?

Thanks again

[shallowwatersailor 3,214]

I had an '89 520-H that had the exact same problem. I spent a lot of time trying to figure it out along with some of the other symptoms it exhibited. I finally bought an ignition switch, swapped it out, and - Voila! - it ran. 

[lynnmor 7,727]

That white connector near the battery is the source of much electrical problems on a 520H.  Unplug it and look for burned or corroded contacts.

[Kurt-NEPA 755]

My seat switch was bypassed also.  That is not unusual.  Check how the wires were connected to bypass the seat switch.  Mine wire were just twisted together and corroded.  A simple crimp on butt connector fixed it.

As others have suggested, Check the ignition switch.  I would pull off the connecter, clean both the male and female ends as best you can. Then check it out.  This is a problem area on the 520H.  Checking the 9 pin white connector is a good idea also.

[Skreegy 0]

Hello folks,

Many thanks for the responses.  Gwest, Kurt, Boomers, Shallowwater, Lynnmor - feel honoured that you have replied.

Currently pouring down in 'sunny' Shropshire UK...so am in the garage stripping , cleaning, checking, making new connectors etc. Your suggestions certainly seem accurate...the wiring connectors are all in very bad condition. Also the ignition switch itself seems to be less than positive in it's actions! Trying to source a new switch in the UK is a bit of a problem , well quickly anyway, but sort of used to that as am a bit of an American fan when it comes to machinery, ...having owned Camaros,Chryslers, Harleys and 3 Toros.
Thanks again. Will keep you updated. Apologies if I am boring you.

Skreeg.

[Skreegy 0]

Key switch on my 520. 'B' badly corroded - 'R' has no wire attached.
Switch is marked as '111216' - am I right in assuming this is the part number?

Thanks again.

Edited August 11, 2015 by Skreegy

[gwest_ca-(File Mod) 11,393]

111216 has been replaced by 103990 - very popular

http://www.partstree.com/parts/search/parts/?searchTerm=111216

Garry

[Kurt-NEPA 755]

Here is the meaning of the letters



As you can see, R is not used.  B is Battery - 12V from the battery positive.  Corrosion on the B spade might be your problem.  I would clean it up both the male and female parts as best you can and give it a try.

Kurt

[Skreegy 0]

Hello All,

Just hoping someone can check my reasoning out please :-

Current status of problem. I have -

• Fitted new ignition switch
• Checked all connections -made good a few faulty ones and cleaned and continuity checked all of them
• Have correct voltage to coil both on 'run' and 'crank'.
• coil primary and secondary windings both within correct parameters
• followed steps for checking ignition module by using voltmeter across negative coil terminal and earth. I think this is the issue as I never show 12 volts at any flywheel position (reads 0.970 v) and there is no fluctuation of voltage as I turn the flywheel.
• I still get no spark at plugs, except when turning key from run to off, then I get a single spark at each plug.

My thinking is that I have a faulty ignition module, although I am concerned that I never get 12 volts at any position.

Your views would be very welcomed. Please accept my apologies for this 'dragging' on.

Thanks for reading,
Matt. Edited August 15, 2015 by Skreegy
more inormation

[KC9KAS 4,744]

Skreegy.. and Wheel Horse's
You are doing a fine job of explaining your problem. You are also handy with a multi-meter, and this is very helpful when members are diagnosing a problem from a thousand miles away!
I have a 520 (Onan) and haven't messed with it much, but others on here are "experts" and should give you additional info on the ignition module.

[WNYPCRepair 1,923]

Have you checked for a corroded ground? That would result in lower voltage, as the corrosion will act as a resistor
 

[cheesegrader 433]

I'm far from expert on electrical issues, but I am being forced to learn the hard way.
I thought the voltage should change by 1.5 volts each time the flywheel comes around, and that failure to read this indicates a bad ignition module.
Expensive little beasts at about $75 dollars.  I couldn't get my flywheel off, and had to get help.

[Skreegy 0]

Hello, and thanks for the comments.

Checked the earth's, cleaned etc. no change to the readings across the 'flywheel'. I am of the opinion that it is the trigger module. Removing the flywheel has beaten me at the moment, so 'Mr tractor' is laying 'in state' in the work shed. Luckily it's getting close to 'grass not growing' for a few months!

[WNYPCRepair 1,923]

Hello, and thanks for the comments.

Checked the earth's, cleaned etc. no change to the readings across the 'flywheel'. I am of the opinion that it is the trigger module. Removing the flywheel has beaten me at the moment, so 'Mr tractor' is laying 'in state' in the work shed. Luckily it's getting close to 'grass not growing' for a few months!
 

If you have ruled out the low oil pressure switch, etc., then I would think it is the ignition module, according to the manual. I just wonder why you aren't getting 12v

 

 

 

Edited August 23, 2015 by WNYPCRepair