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post #1 of 18 Old 11-04-2018, 03:09 PM Thread Starter
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Onan B48M solenoid/starter

I have an early 80's Case 448 with an Onan B48M engine and it is having what I assume is a solenoid problem now that the weather is getting colder. The starter will turn but not engage with the flywheel. It seems to be that if I aim a heat gun into the gap in the sheet metal at the front of the starter for a few minutes, I can get it to start, and if I run it a while and turn it off, it will usually start again, though temps are only in the 40's and I assume this will get worse as it gets colder. Is there grease in the solenoid that might be stiffening up in the cold? Should I just replace the solenoid or the whole starter, and about how long should the job take? I have read a description of the work but it had no indication of the time or difficulty of the job. Thanks, Larry
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post #2 of 18 Old 11-04-2018, 03:31 PM
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Re: Onan B48M solenoid/starter

Unless they did something totally different on the B48M that is a mechanical bendix. Yes, if the lube gets sticky it won't engage the flywheel. I suggest you pull the starter off and clean everything up with some good solvent.

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1978 Case 446
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post #3 of 18 Old 11-05-2018, 07:45 AM Thread Starter
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Re: Onan B48M solenoid/starter

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Originally Posted by mendonsy View Post
Unless they did something totally different on the B48M that is a mechanical bendix. Yes, if the lube gets sticky it won't engage the flywheel. I suggest you pull the starter off and clean everything up with some good solvent.
Can you tell me roughly how long the job might take?
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post #4 of 18 Old 11-05-2018, 08:55 AM
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Re: Onan B48M solenoid/starter

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Originally Posted by larrypac View Post
I have an early 80's Case 448 with an Onan B48M engine and it is having what I assume is a solenoid problem now that the weather is getting colder. The starter will turn but not engage with the flywheel. It seems to be that if I aim a heat gun into the gap in the sheet metal at the front of the starter for a few minutes, I can get it to start, and if I run it a while and turn it off, it will usually start again, though temps are only in the 40's and I assume this will get worse as it gets colder. Is there grease in the solenoid that might be stiffening up in the cold? Should I just replace the solenoid or the whole starter, and about how long should the job take? I have read a description of the work but it had no indication of the time or difficulty of the job. Thanks, Larry
You need to check the electrical health of the components. The reason is if you are dropping a volt or so along the way, it may be hard to notice, you may not be spinning the starter at full speed.

You start at the battery and end at the starter. Are both battery cables clean and do they both have quality battery terminal ends?

If you want to just replace an item that is the most common problem, replace the ignition switch which you can buy from a Case parts dealer. The switch is very odd and not found elsewhere.
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post #5 of 18 Old 11-05-2018, 09:05 AM
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Re: Onan B48M solenoid/starter

That depends on how difficult it is to remove your starter. I think that the B48M requires you to remove the front shroud to get at it. I cut out a small opening in the shroud on my B43M so I could get at those two bolts without pulling the engine.
It will probably take about half an hour to clean and lube the bendix not counting the time to remove an re-install the starter. Spray it with some good solvent several times to get all the old sticky stuff out then lube it with a little bit of fresh motor oil.

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1978 Case 446
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post #6 of 18 Old 11-05-2018, 09:17 AM Thread Starter
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Re: Onan B48M solenoid/starter

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Originally Posted by ssmewing View Post
You need to check the electrical health of the components. The reason is if you are dropping a volt or so along the way, it may be hard to notice, you may not be spinning the starter at full speed.

You start at the battery and end at the starter. Are both battery cables clean and do they both have quality battery terminal ends?

If you want to just replace an item that is the most common problem, replace the ignition switch which you can buy from a Case parts dealer. The switch is very odd and not found elsewhere.
Is the ideal that I will check at the battery and not have any drop in that voltage all the way to the starter? Also if I short across the solenoid terminals and still have the problem, does that eliminate the ignition switch as the problem?

Last edited by larrypac; 11-05-2018 at 10:19 AM.
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post #7 of 18 Old 11-06-2018, 01:24 PM
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Re: Onan B48M solenoid/starter

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Is the ideal that I will check at the battery and not have any drop in that voltage all the way to the starter? Also if I short across the solenoid terminals and still have the problem, does that eliminate the ignition switch as the problem?
If you have battery voltage at the starter and jump the solenoid from there and have the same problem then it is the starter. That is assuming that you have good cables and connectors that can carry the amp draw. I have a drawer with a lot of undersized former battery cables.

I would research what type of lube is needed. I cannot recall what kind is used but I don't think it is just oil. You may be able to use the straw and get brake cleaner on it. Be careful about making holes in the tins, unless you are also going to patch them. That cooling air is needed very much.
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post #8 of 18 Old 11-10-2018, 09:02 PM
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Re: Onan B48M solenoid/starter

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If you have battery voltage at the starter and jump the solenoid from there and have the same problem then it is the starter. That is assuming that you have good cables and connectors that can carry the amp draw. I have a drawer with a lot of undersized former battery cables.

I would research what type of lube is needed. I cannot recall what kind is used but I don't think it is just oil. You may be able to use the straw and get brake cleaner on it. Be careful about making holes in the tins, unless you are also going to patch them. That cooling air is needed very much.
The shroud does not have to be removed I remove all the side bolts on the starter side so I can pry the shroud away as far as it will, then get your self a ratchet swivel wrench also have a box wrench and open end wrench handy it will take a few minutes but that is how I do it. Some say they pull the engine some take the front apart so the shroud comes of all that is a lot of work and a waist of time
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post #9 of 18 Old 05-24-2019, 11:47 AM Thread Starter
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Re: Onan B48M solenoid/starter

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Originally Posted by mendonsy View Post
Unless they did something totally different on the B48M that is a mechanical bendix. Yes, if the lube gets sticky it won't engage the flywheel. I suggest you pull the starter off and clean everything up with some good solvent.
Is there any chance you might post a photo of the cut you made in the sheet metal? I don't want to make a cut and find out it was in the wrong place. Thanks, Larry
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post #10 of 18 Old 05-24-2019, 12:20 PM
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There is no cut. When you go down the road of having your tractor to make repairs, why bother. You more often have a voltage problem anyway.

But, if you want to hack at your tractor, it is your tractor.

Can you tell me how many volts you have at the battery?
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post #11 of 18 Old 05-24-2019, 05:50 PM Thread Starter
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Re: Onan B48M solenoid/starter

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Originally Posted by mendonsy View Post
That depends on how difficult it is to remove your starter. I think that the B48M requires you to remove the front shroud to get at it. I cut out a small opening in the shroud on my B43M so I could get at those two bolts without pulling the engine.
It will probably take about half an hour to clean and lube the bendix not counting the time to remove an re-install the starter. Spray it with some good solvent several times to get all the old sticky stuff out then lube it with a little bit of fresh motor oil.
Would you mind posting a picture of where you cut the sheet metal? I don't want to start cutting and find out I cut in the wrong spot. Thanks, Larry
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post #12 of 18 Old 05-25-2019, 04:47 PM
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Re: Onan B48M solenoid/starter

Here's a picture of the cutout I made. It is just big enough to get a 3/8" ratchet and shallow socket on the bolts to loosen them.
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2004 Kubota B7500HST
1978 Case 446
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post #13 of 18 Old 05-25-2019, 05:50 PM Thread Starter
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Re: Onan B48M solenoid/starter

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Here's a picture of the cutout I made. It is just big enough to get a 3/8" ratchet and shallow socket on the bolts to loosen them.
Much appreciated. I had started to remove the fan/clutch etc and concluded that it was way more involved than I wanted to deal with. I really don't care about keeping the tractor perfect, I just want to be able to use it when I want. LP
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post #14 of 18 Old 06-02-2019, 07:26 AM Thread Starter
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Re: Onan B48M solenoid/starter

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Here's a picture of the cutout I made. It is just big enough to get a 3/8" ratchet and shallow socket on the bolts to loosen them.
What did you cut it with? A Dremel seems too small and a 4-1/2" grinder too big. LP
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post #15 of 18 Old 06-02-2019, 08:34 AM
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Re: Onan B48M solenoid/starter

I made a small cover plate to go over the hole to access the bolt . I fastened the plate with 2 short sheet metal screws. It is important to keep the circulating air in the shroud for the cooling of the engine
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