MS 290 Oil Pump Replacement

[Wood Doctor]

I decided to replace the oil pump and the suction hose after an MS290 stopped oiling. It could be that just a loose drive spring that mates with the worm was all that is wrong. However, I ran into a major obstacle -- removing the suction hose. Hose removal has been an impossible mission. Check these two diagrams from the service manual:

The hole in the engine housing is so small that the grommet will not pass through it and thus cannot be pried up. That grommet kisses and affixes to the hole in the oil tank, not to the hole in the engine housing as shown in the first diagram. The short end of the suction hose attaches to the pickup body, correctly shown in the second diagram. Also, attaching the pickup body to the suction hose if the hose is already positioned in the tank looks to be another virtual impossibility. So, installation of a new hose and pickup body seems to be a huge challenge as well.

Has anybody else run into this and if so, how did you solve it?

 

[Jasonrkba]

I have not replaced mine but I'll give it a shot. I imagine the hole is the same diameter as the pickup going in already attached to the hose. Is it possible that the rubber grommet has hardend making it difficult to remove?

 

[Chevboy0167]

Strange.... I just replaced the oil/fuel tank assembly on a 290 i got here. I had no problems at all removing and re-installing the oil hose with the pick up attached to the hose. They slid right in the new lower unit hole.

The first pic is correct on the REMOVAL of the tube. Also the hose with pickup attached goes in, (in reverse order), just like you pulled it out.

 

[Jasonrkba]

Also are you the first owner? Maybe it leaked before and someone used motoseal on it?


Assuming all is OEM.

 

[HarleyT]

The replacement of an OEM hose and filter is not too hard. The filter goes on the hose before it is installed.

 

[Wood Doctor]

The replacement of an OEM hose and filter is not too hard. The filter goes on the hose before it is installed.

Thus when installing the new hose, you come in from the tank first and press the hose through the larger hole in the tank with the pickup body attached. The second diagram on the right is correct.

As it stands, I will have to destroy the old suction hose. It cannot be pulled out of either the tank's hole or the case hole, which is smaller than the tank's hole. The larger portion of the grommet, as indicated by the red arrows, blocks removal completely. I will have to cut the hose on both sides of the grommet and say good bye to it.

 

[HarleyT]

I am not sure what you mean.

 

[Wood Doctor]

The first pic is correct on the REMOVAL of the tube. Also the hose with pickup attached goes in, (in reverse order), just like you pulled it out.

So, how did you get the large potion of the grommet through the case hole so that you could pry it out? That is what cannot be done. The diagram shows that larger portion already through the case hole.

 

[Wood Doctor]

I am not sure what you mean.

It means I cannot at this point remove the old suction hose either from the tank side or the case side. It's sealed in between the tank and the case by the large portion of the grommet.

Looks like I need to remove the saw's big outer handle so that I can get to the gap between the case and the tank from underneath. I was hoping to avoid that.

 

[HarleyT]

This is what the OEM one looks like, it fits in much like their fuel lines.

 

[HarleyT]

Too be honest, it is very rare to have to replace one, let alone remove one.

 

[Wood Doctor]

That picture in Post #10 is exactly what I have (OEM). I unfortunately separated the pickup body from the hose and inserting that back into the existing hose while installed in the tank cannot be done because I cannot pull out the hose from either the tank side or the case side. As I said in post #9, it looks like the outer handle, once removed will allow access from underneath to remove the hose.

 

[cookies]

to replace it yoy must remove the handle, insert and remove from under the saw body...not from inside the oil tank.

 

[HarleyT]

Oh, you need to be able to get to it.

I never have tried to do one that way.

 

[Wood Doctor]

To replace it you must remove the handle, insert and remove from under the saw body...not from inside the oil tank.

Correct! That front handle must be removed in order to get to the bottom. Those diagrams I show in Post #1 are all showing the bottom of the case and the tank. That was the problem, and now it is solved. Thanks guys!

 

[cookies]

modified more than one ms290 oil pump for higher output

 

[Wood Doctor]

modified more than one ms290 oil pump for higher output

This oil pump was producing nothing at all. Owner (tree service company) almost ruined the bar. His operator said things were smoking a little, an understatement of the year. I have machined the bar, and it looks to have enough depth in the groove remaining to run another year or so. The engine has good compression, starts, and runs strong. After the new pump is in, I'll report back, but I believe we have saved another saw.

 

[Chevboy0167]

My old hose and pickup screen are in good condition so I popped it out of the broken lower unit and used a squirt of silicone spray to re-install it into the new lower unit. No problems at all with the OEM filter setup. I could see maybe a problem with an aftermarket filter and/or hose if they are not the correct sizes.

Just finished her 30 mins ago...

 

[cookies]

That style pump gets sawdust into it around the pump shaft clogging it and wearing the pump shaft when the tank is never cleaned out. You can drive the pump pin out to clean its bore out, the output elbow o ring should be replaced if disturbed and the case vent as well since the valve likes to hang open from sawdust causing the tank to slowly empty or clog preventing the tank to go under vacuum restricting oil flow. Those oil pumps are under sized and completely relies on high rpm to put any oil out and really should have a finer mesh pickup filter. If it has a aftermarket cylinder or any other rpm limiting problems it will never oil properly. The ms290 must run at 12,500 and ms390 at 13,000 rpm or its oil pump will fail to properly oil 18-20" bars or may not oil at all. Once I modify the pump it will lube a 20" 3/8 bar/chain really well even at lower rpms. I have fought these pumps over and over owning 3 of these saws. Their great saws for ground cutting ,bucking etc with a 20" bar because they are pretty low vibration, run a long time per tank fill and their lack of serious power keeps kickback pretty mellow. If you want to fell using it I would highly suggest a 16" bar or use a different saw with more grunt.

 

[Chevboy0167]

Thanks for the heads up cookies. If mine fails to oil properly or to my liking, I may ask for yer secret on the modification if you wouldn't mind. My 310 has been oiling the 20" bar with no problems as of yet for my needs. Thank you.