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  1. #1

    Default Onan 6.5 genset spark plugs

    I have an Onan 6.5 gas genset. It's in a 1985 Trojan but on the original bill of sale of the Onan genset there is a stamp saying Sept 1984. I'm having trouble starting it. I think I've narrowed it down to a fuel issue. It turns over fine and if I pour gas down the carb it runs until that gas is used up. But without that fuel, nothing is entering the carb when it's turning over and the fuel pump bowl is dry when I pulled it off so I'm thinking it may be the electric fuel pump. Could there be another issue or should I just order a new fuel pump?
    My other question is about the spark plugs. They are Autolite 2247 (shielded). They seem to be working fine but I thought I should have a spare set. I can't seem to find them anywhere. A cross reference gives me Champion XMJ20. Amazon.ca has them but when I look at the picture there are no external threads on the shielded part where the plug wire screws on. So does that mean the Champion XMJ20 is not the right plug? The model number of the genset is MCCK-3CR/2268H serial number G840 18392
    Thanks to anyone that replies

  2. #2
    Join Date
    Sep 2008
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    Default Re: Onan 6.5 genset spark plugs

    Highly likely the dry bowl is due to the fuel pump not working. I would check the power to the fuel pump before replacing it. Sometimes there is a low oil pressure cutoff switch in the line, similar to that used on the main engines. sometimes that switch will kill the ignition via a relay. I'd change all the relays as they are cheap and only have a finite lifetime...either way, the service manual should tell you what is there and how it operates.

    The dates listed are not unusual...many parts will be 'earlier' than the date on the hull..

    The www and a search engine will help you find some alternates for the plugs. Just takes time. You can always go by the local Onan service desk and see what they have to offer...

  3. #3

    Default Re: Onan 6.5 genset spark plugs

    Thanks makomark. The schematics show 4 relays. start solenoid, crank ignition, run ignition, and stop. According to the schematics, the numbering of them appear to be similar to simple automotive relays ( 87, 87A, 85, 86, 30 ), with the exception of the start solenoid relay. Since it will fire up once I pour gas into the carb, should I assume that one is ok, and just buy the other 3 regular auto looking relays? Or try to get them all at the Onan service desk?
    As for the spark plugs. The onan parts guy and Onan mechanic said "good luck with that one" Not only are they extremely rare to find, if not impossible, the last time that they could find plugs they were $1200.00 (CAD) each. But they came with the SS braided plug wire so that would make it well worth a second mortgage I suppose. haha.

  4. #4
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    Default Re: Onan 6.5 genset spark plugs

    Wow!! I've heard there are some older gensets that have that ignition setup. also have heard there is a similar model that has a more conventional ignition and some have switched to it. Check onan parts dot com - w/o spaces - they were in my notes and may be able to help....

    As far as the relays go, I haven't seen a 'marine' one that was worth the premium tied to it. I use the auto style and encourage keeping spares on hand. Honestly buying them online is cheaper unless you need them 'today' then the local Napa or whatever is closest is the place to go.

    Good that it fires up with the carb being filled manually....you need to figure out why they pump ait working....could be restriction in the pickup (anti-syphon valve maybe?), electrical supply problem, or the pump needs overhaul or replacement. you could use an outboard tank to help troubleshoot but you need to take appropriate precautions....you can also provide a fused feed direct to the pump to check its status.

  5. #5

    Default Re: Onan 6.5 genset spark plugs

    Thanks for the link to Onan parts. I went there and saw an image of the Champion shielded plug and it shows external threads on the shield so that's a good sign. $21.00 USD each so I can live with that.
    I'll just roll up my sleeves and start eliminating things. I'm just spraying the fuel line threads with liquid wrench to free it up so I can put on a temporary fuel line running to a gravity fed tank. So far a flare nut wrench won't loosen it, but i have time and patience on my side.
    Thanks again makomark

  6. #6
    Join Date
    Sep 2008
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    Default Re: Onan 6.5 genset spark plugs

    wow - that beats $1200 is either currency!!

    when it comes to flare nut wrenches, I only trust my old snap-ons....I got almost new ones for metric so haven't test them thorough - all our metric stuff is relatively new....sounds like a reasonable plan....be careful.

    There's another guy that's excellent with Onans - my phone entry call him "boomer' bob....I sure you can find him on the www like i did.

  7. #7
    Join Date
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    Default Re: Onan 6.5 genset spark plugs

    make any progress??

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