Stihl MS250C not oiling mystery

[Takoateli]

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 asked if 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 a 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

[dougand3]

Welcome. I don't know this model but some brainstorming...
The crankshaft does turn the worm gear which turns the oil pump when running? Some worm gears look good but don't continually turn pump - ie, there is a dead spot.
Air leak, so no pressure builds? Maybe missing or damaged  O ring?

[Gearbox]

I had a 044 that wasn't oiling well so I wasn't out anything also leaked when sitting . I mixed 50 /50 oil and atf dex-merc  and flushed it thru . Just ran it on a piece of cardboard until it started to oil .  Must have  cleaned it out works now . dump the cleaner and refill.

[hawkins111]

Spring not in notch on sprocket or spinning on worm gear.

[Gearbox]

Good thought Hawkins 111 if the clutch has been apart

[skipster]

I had a brand new one with the same problem,got sick of trying to sort it out and sold it,then bought an 044. Much happier now!

[Texas-Jim]

Pull the sprocket off and look to make sure the oiler spring is engaging in the sprocket fully. Then pull oil line off the pump and wait a few minutes see if oil comes out the hose. Gravity will pull it out after a bit. The pumps them selves rarely fail, but since you had it out did you line it up properly? There is a flat spot on the pump that lines up with notch on the body of saw. They can only work if its in right spot and the right depth.

[Stihlowner]

I don't buy what you were told about the oil hurting the pump.
Basically bar oil has a tacking agent in it so it sticks better than regular oil.
I sometimes spray my chain before cutting with motorcycle chain oil in the spray can.
That stuff really sticks.

[Texas-Jim]

stihlowner i agree, if pull one apart theres nothing in one that oil could damage, at least nothing i can see.

[joe_indi]

..................... 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......................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.

Takoateli, it would seem you have lost the dummy plug as shown in the picture below.It is in front below the muffler on the left side.To check if this is the cause, start up the saw and see whether oil comes out at the point in Orange in the diagram You could use a screw as a replacement but it should not be too long. Maybe 2mm long. Joe

[Texas-Jim]

Joe that is a vent, it wont stop one from oiling. But if its leaking that could be cause.

[joe_indi]

It is not a vent. The vent to the oil tank is at the side close to the studs for the guidebar.
This hole is formed during the molding process of the oil passage. It is blocked using a plastic dummy plug, which at times comes off with the combination right amount of heat and pressure of the oil pump, usually a temporary clogging.Once the dummy is out you get a drop at the guidebar but a flow at this point. Below is a rough diagram of the oil flow. The outlet to the guidebar is small compared to the oil passage from the pump. Once the dummy plug is out it is a free flow passage through that hole below the muffler

[Texas-Jim]

yea  i bad, forgot 250 doesnt have supply tube. Ignore me.

[currantvt]

I think Joe is on the right track, I had the same problem with my 021 and it was that plug missing. With mine it fell out while using summer oil during the winter and I've wondered if that put extra pressure where it shouldnt.

[motohed]

I know this is a no brainer , but have you cleaned the bar grove and the oiler hole in the bar , many people look way to deep for an oiler problem , this is by far the most forgotten problem with oiling .

[Bigfoot870]

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.

What did you use?

Apparently some folks use "vegetable" oil.

I have a friend whom only used used (car) engine oil in his Husqvarnas. He cuts logs and firewood, year round and his Dad is a retired small engine tech, with over 20 years at a Husqvarna / Jonsered dealer. Personally, I'll stick with proper chain oil.

Just curious