Author Topic: Stihl MS250C not oiling mystery  (Read 1487 times)

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Offline Takoateli

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Stihl MS250C not oiling mystery
« on: April 27, 2016, 06:14:33 pm »
I have a Stihl MS 250 C chainsaw which is not oiling the bar.  I've done a lot of googling, and watching YouTube videos, and I even contacted the company. I still can't get to the bottom of the problem.

First I checked the basic things like a clogged oil pickup screen in the oil tank, clogged passageways, damage plastic worm gear, and none of those seem to be a problem. All the passageways are clear, the plastic worm gear is in good shape and when I spin it around by hand the oil pump turns. But when the pump is running without the bar on it no oil comes out the oil port.

I stopped in at the local representatives and showed him my oil pump. I estimate it might be bad. He asked me if I had run other oils besides bar oil and I told him yes. He said sometimes that can damage the oil pump. So online I ordered an aftermarket oil pump, not the stainless steel original OEM part, but one of the bronze knockoffs. I just finished installing it and still the machine is not oiling. Before I ordered the new oil pump I tried cleaning the original oil pump with WD-40, gasoline, and the compressor. None of that made any difference either. The original oil pump does not appear to be damaged to the naked eye. It does not appeared scored and it spins freely. On the bottom of the case near the hole where the oil pump goes in there is a diagram which shows in which direction the oil pump should be oriented when it is inserted. The oil pump has a groove and the diagram shows which direction that groove should be facing. I made sure that I installed the oil pump with the proper orientation.

One of the things I read that you could do to ensure that the oil passageways are clean and also to reduce the oil viscosity to aid in pumping is to add some gasoline to the bar oil. I did that and still the machine will not pump oil on its own. With the machine running if I turn it on its side so the bar side is down and the oil tank is up the oil does flow out of the oil port. So I believe that shows all of the passageways are open all the way from the oil tank to the oil port, but for some reason the machine just won't pump oil.

Also the machine does seem to leak a little bit of oil, I'm not sure from where, but I don't think that would be a problem.

Does anybody have any ideas about why a machine with clean passageways, and a brand-new oil pump still won't pump oil?

Thanks

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Offline 660magnum

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Re: Stihl MS250C not oiling mystery
« Reply #1 on: April 27, 2016, 08:00:34 pm »
You make no mention of the drive spring that engages the notch in the clutch drum and drives the worm gear around?   My MS250 had the end of the drive spring arm worn off and the pump wasn't turning when the saw clutch was turning.

It is a part time oiler and only works when the clutch is engaged and turning



Can you see the little notch in the edge of the clutch drum that the arm engages to drive the worm?

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Offline Takoateli

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Re: Stihl MS250C not oiling mystery
« Reply #2 on: April 27, 2016, 09:07:53 pm »
Thanks for the reply! Yes, the drive spring is engaging the clutch drum. I'm at a total loss.

BTW I asked the company and this is their reply:

The only other issue that I can think of that may contribute to this issue is the vacuum relief valve press-fitted into the oil tank. Itís located in the side of the engine housing between the oil output hole and the bar studs. This valve has an internal spring and ball type arrangement with the ball pressed against the vent hole of the casing of the valve. When the tank develops a vacuum from the normal process of the oil being pumped out, the ball is pulled away from the hole, allowing air to enter into the tank and break the vacuum so that oil can continue to flow to the bar and chain assembly. Once the vacuum is relieved, the spring pushes the ball back against the hole of the valve casing. The spring may be broken, so the vacuum in the tank cannot be broken, and therefore the oil cannot flow. You can try taking a small pin or needle and pushing it into the hole of the valve (identifiable as a small silver disk with a tiny hole in the center) to test the strength of the spring. If you donít feel any resistance, the valve is probably defective and needs replacing.

I have checked the relief valve and it's good. I've physically actuated the relieve valve and it's working and it's not the problem. So I'm still at a loss.

Thanks!

Offline jmester

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Re: Stihl MS250C not oiling mystery
« Reply #3 on: April 28, 2016, 08:14:56 am »
Did you make sure all the passages where clear and flowing. Compressed air threw the oil channels. Sometimes the gas mix with the oil will still not dislodge a clog.
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Offline Takoateli

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Re: Stihl MS250C not oiling mystery
« Reply #4 on: April 28, 2016, 10:36:10 am »
Yes, I blew out the passages. If I tip the machine on it's side, bar side down, oil runs out. It just won't pump!

Thanks!

Offline 660magnum

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Re: Stihl MS250C not oiling mystery
« Reply #5 on: April 28, 2016, 10:58:26 am »
It's sucking air
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Offline Takoateli

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Re: Stihl MS250C not oiling mystery
« Reply #6 on: April 28, 2016, 11:00:14 am »
Thanks! Would you suggest replacing the oil tank pickup tube and/or the plastic manifold piece that screws on and connects the oil pickup tube to the orifice the oil pump sits in?

Offline 660magnum

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Re: Stihl MS250C not oiling mystery
« Reply #7 on: April 28, 2016, 11:46:18 am »
Very much so
We should share what we know... someone may learn...
That knowledge can live after us... and that "Pays It Forward".
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Offline Takoateli

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Re: Stihl MS250C not oiling mystery
« Reply #8 on: April 28, 2016, 11:47:34 am »
Thanks! I'll try that and post my results.
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Offline jmester

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Re: Stihl MS250C not oiling mystery
« Reply #9 on: April 28, 2016, 07:43:15 pm »
Make sure you get the o ring that goes on the plastic connector
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