Yellow 587 Oil Pump Issue

[Oscar the Grouch]

New member and new PWC owner here. The last thing I want to do is post a thread on something that has been covered but I just searched for about an hour on my issues and it doesn't look like it was covered.

I have an 89 SP with the Yellow 587 and intact oil injection pump. I really want to keep the pump for ease of use.

The SP runs well has what I would consider 55hp and gets up to plane quickly. So no running issues to speak of.

The problem is the rear cylinder oil line(skinny one) has consistent bubbles in it while the front cylinder line is bubble free and pumping like it should.

Noteworthy Notables:
-both the skinny lines are still soft/pliable. Not hard. And look to be well crimped/sealed at the connections.
-I pulled the pump and bench tested it(counterclockwise with the drill) Both lines pump solid and consistent oil on the bench.
-When I pulled the main oil feed line(from the reservoir) it had positive pressure. Holding the line higher than the tank it was still pushing oil out so I opened the fill cap which let out a puff of pressure.
-I checked the vent tube which allows air in to the tank. Not the other way around.

What am I missing??? Why is the rear line getting air while the front line is working correctly? After my test ride today I and afraid I ruined the rear cylinder but a bore scope in the cylinder isn't showing scoring of the cylinder walls. I will check the compression soon.

Thank you for any help you can give me!

 

[mikidymac]

Replace the small lines even if they look fine. As long as it is pumping oil it is fine.

The check valves on the intake manifold could be leaking letting some air back into the line when it sits.

 

[Oscar the Grouch]

Thanks I'll replace the lines. I don't think it's a check valve because the bubbles come from the pump end and work their way up to the manifold.

 

[Oscar the Grouch]

Does anybody have comments on the pressurized oil tank?

 

[mikidymac]

The check valve on the oil tank let’s air in but not out so in theory it could build a little pressure. Not uncommon.

 

[Oscar the Grouch]

Thanks for the help everybody! I pulled the pump off, replaced the two big o ring seals as well as the little oil pipes to each cylinder. Everything is working properly and the oil tank isn't pressurizing anymore. I'm not exactly sure what is was but I would guess the little oil lines. They were stiffer than the new ones.

 

[Oscar the Grouch]

Pictures

 

[mikidymac]

Congratulations!