Mcculloch Power Mac 310 oil pump inop

[kenmpls]

I have a McCulloch Power Mac 310, model 600042D, serial #14-014429 with an inoperative oil pump. The pump does not pump oil either with the manual button or automatically when running. The pump does not suck oil out of the oil tank. All of the hoses, oil passages, and the screen in the oil tank are clear. I removed the pump and covered the 'piston port" from the engine and the manual pump button still does not suck oil from the reservoir. I'm thinking that there must be a check valve somewhere in the pump or screen that is sticking open. Anyone know if or where a check valve is located? Is replacing the pump the only option? Thanks for any comments.

 

[heimannm]

This is the oil pump from a Mini Mac but the one on the 300 Series saws is similar. If you work the piston manually the oil should move through the pump. The inlet is as 5:00 and the outlet is at 11:00. The manual pump on the 300 Series is right on the pump body where the inlet is on the Mini Mac pump and the inlet is on the end of the pump with a cap that presses in place fit with a nipple for the inlet hose.


There is a steel sleeve pressed inside the pump body with a hole for the oil inlet, and a ball and spring check valve in the bottom, of the hole.



If you cannot free up the check valve with some brake cleaner or carburetor cleaner, you can carefully disassemble the pump by grabbing the sleeve and twisting / pulling it out. Note exactly how far the sleeve is pressed into the pump body as the hole must line up with the inlet port in order for the pump to work when you put it all back together.



The 300 Series pump.



The biggest problem I have had with the 3oo Series saws is getting a kink in the inlet hose that pinches it off preventing any oil from flowing.

Mark

 

[kenmpls]

Mark, Thanks very much for the excellent detailed photos and comments. I never thought about a check valve in that location but now it makes sense. I'll work on it this week. Also, it appears that air pressure pulses from the motor drive the piston as I can see no drive rod or cam. Is that correct? Thanks again.
Ken

 

[heimannm]

That is correct, McCulloch used the impulse operated automatic oil pump on many models over the years.

Mark

 

[kenmpls]

Mark, Thanks again!