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Old 01-08-2021, 10:47 PM   #1
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Updated coil

I am wanting to replace the coil on my Onan 6.5 generator. I am replacing the old (original) coil and need some advise on the wiring. Aside from the plug wires --- the old coil has 2 wires. 1 wire goes into the points and the 2nd wire goes into what I'm assuming is a DC (12v) feed. The negative or ground is on the metal plate on the side.



The new coil has 2 connection ----- clearly marked ---- + and -. I'm assuming the 2 wires for the old coil connection both go to + (positive) but I would feel better if someone can confirm this.



I was going to add pics, but apparently I don't know how -- The old coil is the military style with the braided plug wires. The new coil is just a standard 2 plug wire coil. ---



Base on this sketchy description, can someone offer advise? -- Thanks
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Old 01-08-2021, 11:25 PM   #2
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Do you know which model of Onan it is?
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Old 01-09-2021, 12:40 AM   #3
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+ goes to 12v feed. (-) goes to breaker points.

Coils rarely fail on those old MCCK's. Check points, that they are clean and set right, also check condenser. Seen a few condensers fail on those.

Got a coil in my shop (I think) if you really need one.
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Old 01-09-2021, 01:27 AM   #4
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I've got the service manual for that one. Please find attached.

The wiring of the ignition coil is shown at the top of page 46.

Testing the coil looks pretty much like on any other engine.

From the manual:

Coil: If spark is weak (or there is no spark) and the breaker points are clean and properly adjusted, test the coil for possible defects. As a general test of the coil, disconnect the spark plug leads, ground one and hold the second lead 1/4" from the engine. Then crank the engine. A good spark indicates the coil is operating. Test the coil as follows: Using an ohm meter, check the resistance of the coil windings. Normal resistance readings range from 5 to 2 ohms for the primary winding and from 4,000 to 10,000 ohms for the secondary winding. Extremely low resistance usually indicates a shorted winding and extremely high resistance usually indicates an open in the winding. The 4-volt coils can be tested on a 6-volt tester. However, a 12-volt tester will destroy the coil.
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File Type: pdf OnanMCCKServiceManual.pdf (3.12 MB, 6 views)
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Old 01-12-2021, 02:46 PM   #5
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gkesden, I'm headed to the boat tomorrow to install the coil. I am running into a problem trying to get a good parts number for spark plugs. The old ones are the military grade for use with braided wires. My auto parts guy can't find a cross reference for a standard type plus.The plugs that came out (for use with the old coil) are Champion XMJ20.



The later model 6.5 uses a plug with a longer reach. The Champion XMJ20 has what I calculate to be a 3/8 reach.


With all this said ----- any suggestions on a plug?


Thanks
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Old 01-12-2021, 02:58 PM   #6
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Hi TRD,

I'm a bit confused. Champion XMJ20's are Champion part #573, no?

-- https://www.oreillyauto.com/detail/b...ug/573/2623280

-- https://www.amazon.com/Champion-573-.../dp/B000CSRE40

-- https://shop.advanceautoparts.com/p/...573/20650067-P

-- https://www.napaonline.com/en/p/CHA573
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Old 01-12-2021, 02:59 PM   #7
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If the points are being even remotely finicky, hunt down the (discontinued) electronic ignition conversion. I found a NOS one and installed it last year and my MCCK runs better than I ever remember. At some point I should probably replace the 35 year old plug wires, so I'll probably put on a new coil for an RCCK and convert it to the non RF shielded plug wires and plugs (the RCCK was the non-marine version of the same engine).
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Old 01-12-2021, 03:04 PM   #8
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Maybe I didn't explain well enough my problem. -- The plug you show is the type plug that was in the generator when I was using the old style coil --- that has the 'screw" type wire connectors.



What I need now ----- with the new style coil are automotive type plugs that accommodate automotive type plus wires and connectors.



Does that make sense?
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Old 01-12-2021, 03:05 PM   #9
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Okay. What is the part number for your new coil?

-Greg
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Old 01-12-2021, 03:08 PM   #10
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Quote:
Originally Posted by TRD View Post
Maybe I didn't explain well enough my problem. -- The plug you show is the type plug that was in the generator when I was using the old style coil --- that has the 'screw" type wire connectors.



What I need now ----- with the new style coil are automotive type plugs that accommodate automotive type plus wires and connectors.



Does that make sense?

Sounds like you've already done the conversion to the RCCK style coil and standard plug wires.

I found this on another forum as a plug cross reference:

Quote:
I show stock plug for your MCCK as Champion XMJ20
14mm, 3/8 reach, shielded connector, heat range 20

Equivalent plugs:
Champion J19LM or RJ19LM
Autolite 458
NGK BR2-LM

These are all 14mm, 3/8" reach with normal connectors. Same heat range
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Old 01-12-2021, 03:23 PM   #11
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Thanks --- that's what I needed ------ will pick up a couple of plugs on my way up to the boat ---
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