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Onan no spark headaches

Discussion in 'Large Equipment' started by FlyingDutchman, Oct 9, 2019.

  1. FlyingDutchman

    FlyingDutchman Row Seatin'

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    Onan B43M in a Gehl HL360 skid steer. Same engine as in many older JD rider tractors. No spark or weak spark. Fires the coil at the same time for both cyls. Machine ran 10 years ago, but had a governor failure.

    We have fuel, compression. Points are new, are gapped to spec, and close at the appropriate times. Have to have the lights off, someone leaning on the plug with a screwdriver to ground to see a weak orange spark. The current setup has the condenser on the GROUND side of the coil.

    Coils are NLA or on national backorder for this engine. NOS is $214.

    The Onan book says the secondary coil resistance across the pins for the plug wires is 12-15K I have like, 34k ohms.

    The condenser is unknown but looks new.

    Aftermarket (Chinese) coils include a different style of condenser, and the coils have a higher ohm reading (on par with what I have), which if you go on the Onan parts website, say these style condensers go on the positive side of the coil. https://onanparts.com/index.php?mai...id=180&zenid=2e485b4c797899f7e1d0d0b3b830f5e5

    I have an aftermarket coil on order but despite ebay saying I'd have it today, its coming from a California Chinaman hellhole and won't be here till next week. Need this machine for a job this weekend, frustrated and stumped and pretty much out of funds to fix it.
     
  2. mrhemihead

    mrhemihead ArboristSite Member

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    Questions...
    Do you measure 12V at the + on the coil with the ignition on run? If there is ballast resistor on that engine it will be somewhat lower.

    What do you measure at + while cranking? No you wont get shocked by doing this. It should be 12V or battery terminal voltage, whichever is higher.

    The condenser on - is correct but that's not ground. - goes to the points.

    You could temporarily disconnect the condenser to see if it starts. The condenser prevents the points from burning up, but for testing purposes no worries.
     
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  3. FlyingDutchman

    FlyingDutchman Row Seatin'

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    Measured 12.5 volts on key on, 10.5 on crank.

    Haven't tried disconnecting the condenser.

    I do get snapping across the points occasionally if I open and close with a screwdriver. Sometimes. It doesn't happen every time. Dad thinks this points to the coil being bad.
     
  4. mrhemihead

    mrhemihead ArboristSite Member

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    12.5V with key on is good but 10.5V cranking is on the low side. Have you tried jumping this battery?

    The condenser is intended to minimize the snapping so that's not a good way to test. Try a test run without the condenser.

    The condenser listed on the above link mentions electronic ignition. If you have points I am assuming this is not electronic ignition.
     
  5. FlyingDutchman

    FlyingDutchman Row Seatin'

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    The snapping is with the key on, points closed, then manually opening the points with a screwdriver. I'm assuming that this is the condenser discharging.

    The wiring is terrible on this machine, but I don't have the time to redo it 100% yet. I can try a direct jumper wire to the coil for sure.

    Also easy to try to run without the condenser, but it was my understanding you needed it to collapse the field in the coil for spark.
     
  6. uniballer

    uniballer ArboristSite Lurker

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    The coil's field collapses when current is no longer supplied (energy in the field is proportional to the square of the current). The condensor is there to protect the points from being eroded quickly by the sparking (for a little while, the back EMF from the coil is absorbed by the condensor rather than arcing through the points). The condensor must be connected across the points (either directly or through the ground). The expectation is that by the time the condensor is fully charged the points will be opened wide enough that there will be no arcing.

    If you remove the wires from the coil primary you should be able to see the points make and break with a test light as you turn over the engine.
     
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  7. mrhemihead

    mrhemihead ArboristSite Member

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    The condenser suppresses spark transients, caused by the points opening and closing. For testing purposes its OK.

    If the wiring is that bad you could direct wire the coil to the battery, for testing purposes only. Safety first.

    Old school ignitions are very similar. Once encountered a spark issue caused by sloppy bearings on the cam that operates the points. If its setup this way check for side play on the cam. There should be none.
     
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  8. FlyingDutchman

    FlyingDutchman Row Seatin'

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    The JD dealer wants $28 for a condenser, and $244 for a coil. They have 3 in stock of each. What an easy solution.

    Okay, those two tests sound pretty solid. What would removing the condenser do if the condenser was bad? is the condenser creating a short to ground not allowing the coil to charge? I tested resistance across the terminal and the body of the condenser and got milliohms of reading, but not open, and not direct connection to ground. Could not test volts with a DMM (don't know how to use the peak feature quite).

    The wiring is bad enough where I disconnect the ground whenever the machine is not in sight. All the circuits tested good and nothing getting hot but don't trust it, so a jumper wire is a semi-permanent solution to the run time I need.
     
  9. FlyingDutchman

    FlyingDutchman Row Seatin'

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    Uniballer, we are able to see the break with the digital multimeter using resistance measurements. Everything is in order on point break, unless the gap is wrong for my coil type, which has a higher resistance than what OEM was.
     
  10. FlyingDutchman

    FlyingDutchman Row Seatin'

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    This is not electronic ignition, but the fact that these motors may have had it makes parts kind of a crapshoot as the coils look the same. Not sure where they put the condensers on them.
     
  11. uniballer

    uniballer ArboristSite Lurker

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    A shorted condensor is easy to detect with a multimeter, but a leaky condensor, or one that breaks down under stress is not. Does your DMM have a capacitor test range? If so how does the condensor measure up?

    Most likely just about any ignition condensor would work in your engine. This link is informative.

    If I had to go to an auto parts store and get a condensor I would ask if they had one for a 1966 Dodge Dart with a 225 slant 6, just because I could. My local NAPA still has books that cover older industrial and ag equipment (e.g. my 1956 Ford tractor), and they even have some of the parts.

    EDIT: another informative post
     
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  12. mrhemihead

    mrhemihead ArboristSite Member

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    ^^^Agree^^^Do auto parts stores know what a condenser or distributor coil looks like ?:laugh:
    OEM ignition parts are absolutely unnecessary.
     
  13. mrhemihead

    mrhemihead ArboristSite Member

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    Yes, to reduce inventory costs OEM parts are grouped together to match the latest models.

    On an ignition system with points the condenser is connected to the negative terminal, as it was. If it was on the positive post it would not suppress the arching very well.
     
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  14. FlyingDutchman

    FlyingDutchman Row Seatin'

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    Awesome resources here! Learning a ton!

    One of the problems with this one is it fits under a tiny housing very specifically unique from other condensers I've been able to find. could be a challenge to fit "any old condenser" under the housing.

    https://onanparts.com/index.php?mai..._id=53&zenid=2e485b4c797899f7e1d0d0b3b830f5e5

    But I will try to find one and try it out, wouldn't hurt to have one laying around.
     
  15. mrhemihead

    mrhemihead ArboristSite Member

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    Any .3uf 300VDC ignition capacitor will work. Even if the lead needs to be a bit longer to fit that's OK, but the metal body must be grounded.

    If you are in a bind to locate one a radio capacitor with the same specs will work temporarily.

    It's nice to have a dialog going on with this. Typically we provide guidance but there is no feedback.
     
  16. FlyingDutchman

    FlyingDutchman Row Seatin'

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    Found a condenser at Advance, wrong tab but seemed the same, identical size. Hooked up a test lead from the battery to the + terminal of the coil and had spark and the machine ran without swapping out the condenser. The voltage drop on crank caused the no start issue. It will run fine without the jumper if you pull the lead off!


    It's a little smoky running on 50-1 and first fire in 10 years but victory smoke. No leaks and runs pretty decent. Drove it all over the garage. Thanks for the help mrhemihead and uniballer!

    IMG_20191009_203544088.jpg
     
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  17. mrhemihead

    mrhemihead ArboristSite Member

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    Success!
    Thanks so much for the feedback!
     
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  18. FlyingDutchman

    FlyingDutchman Row Seatin'

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    An update on the little fella. I've run about 6 gallons of fuel through it. Burns around a gallon an hour. The governor spring stretched, shortened that to keep the RPM up. Got a bunch of horse stalls cleaned, able to get the damage fixed and the horses in the stalls. Still only about 1/2 done with the job.

    The belt drive, which goes around the crank and up to they hydro sheaves in a triangle shape, slips. I had lots of hydro noise and now it doesn't drive. Can't seem to get the idler tight enough to tighten the belt to drive the hydros anymore, even after adjustment. I got some different springs for the idler, hoping that that will get me the tension I need on the idler pulley, but afraid I may have hit a mechanical maximum on the idler and its fit between the pulleys and the belt. IE, the idler pulley cannot go further between the left hydro and the engine pulleys because its physically too big to fit.

    Praying my $1.90 spring from the hydraulic parts house does the trick getting the tension I need to be back in business.
     
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  19. FlyingDutchman

    FlyingDutchman Row Seatin'

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    No matter how much tension is on the idler, it still slips, 6 times on and off trying more tension and other tricks. I tried polishing up one of the hydro sheaves hoping the belt would grip better, which involved popping the belt off, but now the belt is out of alignment and it got too late to take the idler off again. Also the polishing seemed to make it worse. Looking like a new belt is in order, I think it probably wore vee of the belt so it wont engage the sheave correctly, and the wear on the belt isn't enough for it to fit between the engine and hydro sheaves for "full" belt consumption.

    Changing the belt Involves pulling the fuel tank, engine and a two person alignment procedure to get the engine back in. Unless i can just pull the idler and sneak it under the crank pulley somehow.
     
  20. mrhemihead

    mrhemihead ArboristSite Member

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    I had a similar issue with a commercial lawn aerator which has a hydro transmission. This has two belts driving reciprocating tines. Noticed the new belts were starting to shred when I discovered that too much idler pulley tension caused the belts to twist.

    Setting just enough tension to operate reliably without destroying the belts is PITA.

    The reciprocating crank is too heavy for one person, used the tractor bucket to lift for the belt change.

    A crappy design IMO.
     
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