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Onan B48 - No spark & Points don't move

6155 Views 9 Replies 6 Participants Last post by  robynrj
Got a B48 mounted on my 446, all was good, got it started but it needed a little carb adjustment. (For those keeping score, this was the 18hp Onan and I was fighting a oil leak were the oil filter screws on, replacing the filter adapter has fixed that issue). Had the engine running, ran it for about 5 minutes, checking for the oil leaks at the filter and then I shut it off.

Came back to it about 1/2 hour later and it wouldn't start. No spark....

Took the points cover off to check the point gap and found the points stuck open, when the engine turns, the points don't move. Took the points off and checked everything and found the plunger isn't moving...

Now the cam doesn't were out in that fast, does it? Any ideas of what I should check or do?
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but it sounds like a broken cam gear.
Ugg... yea, I coming back to say that after going back and taking the points off and turning the engine by hand, there's nothing moving under the points pin. Well since so far since this engine was "free", all I have so far is $20 in the filter adapter.

Is a broken cam gear common and assuming it just that, any idea of how much in parts this might cost?

It's a major downer that I just got this put in, it would have been so much nicer had the gear broken when it was sitting on the work bench BEFORE I spent the weekend getting it put in.


In doing a quick look on eBay - are there interchangeable camshaft/gears for a B48M? I see a used on for B43, what typically breaks in these? the gear or the camshaft it's self?? ... 2a0fa3422d
You can pull a head off one side to see if the valves move.

Boomer's your man to talk to.

Broken cam gears do happen.
I don't think the camshaft is moving at all, it's really hard to turn the engine by hand as it appears there's no compression release which I take the valves aren't opening and closing. Can't really turn it by hand until I took the sparkplugs out and it's much easier.

What is involved with pulling the camshaft and what's normally broke in such as situation? Does the camshaft gear teeth break or both the gears on the camshaft and the crank?
I had one go bad last month.There were 5 or 6 teeth missing off the cam gear. The crank gear was also damaged.
you must also consider the OIL pump gear.
give a call if you want 651 437 2826 M/F 8 to 5 pm S and S 12 to 8 pm .
thank you. boomer
boomers_influence said:
you must also consider the OIL pump gear.
give a call if you want 651 437 2826 M/F 8 to 5 pm S and S 12 to 8 pm .
thank you. boomer
I will call ya, it will be in a couple weeks as I heading up a group of scouts going to camp so I gotta set the Case stuff aside for a bit and I want to get the engine off and taken apart so I know what I dealing with.

You comment on the oil pump perked my ears up as I wondered it there was something wrong with it due the oil leak issue this engine had. (leaking from the adapter and filter gasket).

Oil pump only because if cam gear bad pieces damaged crank and oil pump gear too.......take head off to see if valves moving, but either way has to come out to be looked at.....oil pump likely had nothing to do w/adapter leaking.
Bob M
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