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Les Royer 
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Joined: 25 Dec 2014
Location: Carson, Iowa
Points: 5593
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 Topic: Need some help guys
Posted: 09 Oct 2016 at 4:48am |
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Hope you mind helping a green tractor owner, but I'm betting I don't find any better Onan experts anywhere.
Got a B48G motor here running kinda crappy. Pulled the plugs and one is white as can be and the other one a grey color. That usually means fuel mixture but i decided to chase ignition. This is a points and coil motor with 55 hours on the overhaul.
Can't find any reliable specs on checking that coil. Got 4.0 ohms primary, pos to neg, Secondary 13,605 ohms tower to tower.
I also found a .6 voltage loss with 11.77 volts at positive side of coil compared to 12.37 at the battery. Problem traced to connection on back of ignition switch. New wire connector being picked up today.
But I want to make sure I'm checking that coil right. $162 at the green store for one. $87 at onan parts dot com, and there's a $60 one on ebay for probably a Chinese one.
Can ya give me a hand? The nurse wants to mow today. Thanks. Les
Oh, and I prolly should get a manual. Any suggestions?
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I still gots my A/C but it's clear out in the barn now.
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jaybmiller
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Joined: 12 Sep 2009
Location: Greensville,Ont
Points: 22487
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Posted: 09 Oct 2016 at 6:48am |
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Coil primary of 4 ohms is OK to me. It'd draw 3 amps of current from a 12 volt battery. 12/4=3.
An easy 'bench test' is to be sure points are open, confirm 12 volts to coil and use a wire to 'ground' or 'jumper' the -ve of coil to ground. tapping the wire to ground is the same as the points doing it,so you should get a good blue spark on a plug. If you put an ammeter in series - of coil to ground it should read about 3 amps.
The colour of the plugs does sound more like fuel related not coil. If both plugs are same age,they should be same 'colour', unless one cylinder had bad valves.
Jay
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3 D-14s,A-C forklift, B-112
Kubota BX23S lil' TOOT( The Other Orange Tractor)
Never burn your bridges, unless you can walk on water
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fixer1958
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Joined: 13 Feb 2010
Location: kansas
Points: 2434
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Posted: 09 Oct 2016 at 8:01am |
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Running crappy how?
What about the condenser?
I have a 318 that HAD a P Onan engine in it.
Got tired of working on it all the time and put a 24hp Briggs in it
with step up pulley (smaller diameter) for the mower deck.
Sounds like an airplane when you engage the deck.
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tadams(OH)
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Joined: 17 Sep 2009
Location: Jeromesville, O
Points: 10135
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Posted: 09 Oct 2016 at 3:43pm |
Condenser have been know to be bad even when new.
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Dan73
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Joined: 04 Jun 2015
Location: United States
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Posted: 09 Oct 2016 at 4:26pm |
Les I think I can help with this one. Go to this site and look up a carburetor and vacuum fuel pump kit. It is where I got mine a few years back. http://www.casegardentractorparts.comThe problem I had with my case 448 with an onan was that the vacuum pump wasn't pulling enough fuel and there was gunk in the carb both an easy fix. That got one of mine running good for about 5 years till the blow by got too bad and it needed rings. At that point I swapped out the motor. Oh check the fuel line from the tank I had one of them get too old and had to replace it it was sucking air.
Edited by Dan73 - 09 Oct 2016 at 4:31pm
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Dan73
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Location: United States
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Posted: 09 Oct 2016 at 4:44pm |
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Les the only trick i remember about rebuilding those onan carbs with the vacuum fuel pump was to make sure that you look closely at how the rubber bits are in there when you take it apart. I think there are two rubber gasket looking bits that go in that pump one has a small hole in it and one doesn't it is important to get them in the same way when you replace it. The problem is the rubber gets weak with age and doesn't pop back to pump the fuel new rubber and it pumps as good as new.
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Les Royer
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Joined: 25 Dec 2014
Location: Carson, Iowa
Points: 5593
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Posted: 09 Oct 2016 at 7:00pm |
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Ok, I figured it out. It has an intake leak. John deere has gaskets available between intake and block, but this intake splits in half and I used RTV to seal it. Apparently that ain't the thing to use.
Ok, what do I use to seal it up? Why does it need to come apart like that in the first place?
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I still gots my A/C but it's clear out in the barn now.
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Dan73
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Posted: 09 Oct 2016 at 7:34pm |
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Les are your talking about the two halves of the aluminum intake? I think that is just a manufacturing thing so they can stamp them out. I had a problem like that trying to think how I fixed it. I am pretty sure I took it to a parts store and they gave me a fuel rated epoxy I put on the outside.
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Les Royer
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Joined: 25 Dec 2014
Location: Carson, Iowa
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Posted: 10 Oct 2016 at 4:11am |
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I must not have gotten it clean enough the last time when I smeared it over the outside. RTV jest peeled right off.
I drilled those rivets. Came apart pretty easy. Black RTV on the inside. There's a grove where you can lay a bead down. I tapped the holes on one side so I can bolt it back together with 8-32 3/8 machine screws. I guess if RTV worked before, it'll work again. Gonna use the orange high temp stuff tho.
All I need is the intake to block and carb base gaskets. John deere hasn't either of them. we'll see how long the wait iz today. Couple days at most usually.
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I still gots my A/C but it's clear out in the barn now.
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