Mcculloch Mac140 oil pump

[Barn Shop]

Info needed,
I have a McCulloch Mac140 that is leaking pressure from the oil pump while performing a pressure/vac test, I know this is a diaphragm style pump operated by a crankcase pulse like the fuel pump but am unsure if there should be a pressure leak from the pump.
I would think this would cause a lean run condition.

 

[Dream]

You will have more responses if you post in mcculloch thread.

 

[KennyWinCT]

Craig,
Saw this posted in the Mac section. Looks like Mac diaphragm oil pumps (at least this one) is definitely pulsing off the crankcase and would cause what your seeing,

 

[Al Smith]

FWIW the 140 has an impulse piston pump not a diaphragm pump like a 610 .I'm not certain if any of the "mini " models ever had a diaphragm pump .
The mini pumps aren't very good .If they leak which most do they suck bar oil into the crankcase .Enough so it will hydra lock them .Try as I might I've never had good luck rebuilding the pumps on a mini .I think if you research it the faulty pumps are what have caused many of the mini series to become shelf queens .

 

[Al Smith]

What I do ,which is a chitty way to do things is screw the piston adjustment on the pumps so the piston doesn't move and block off the impulse line and use the thumb oiler .