Failed oil pump on my Yanmar 4JH3-HTE?

[penberth3]

Many have anti drain back rubber flaps, all have bypass if blocked valves. Neither would affect my suggestion of injecting air/fuel into the oilway to backflush the strainer.

Thank you. I though you were a bit hasty claiming oil systems didn't have a non-return valve!

 

[Boater Sam]

Thank you. I though you were a bit hasty claiming oil systems didn't have a non-return valve!

There is no non return valve in the pump or the oil ways. Anti drain back "valve" rubber flap in a filter can is certainly not a non return valve in the true sense.

It will be interesting to know what the OP's problem turns out to be.