Vacuum on oil injection....is this normal?

[River Rat]

I have a 1995 27 sailfish with twin 200 mercury EFI. When I open the fill caps for the 2 stroke oil, there's a tremendous vacuum....to the point that it's difficult to open the cap. Shouldn't the oil injection system be vented? Both tanks are doing this.

 

[mboyatt]

I can tell you that the oil injection system is not vented. I have a 1994 OMC 2 stroke and there is no venting on the VRO system. In fact, I believe air intake in the system is bad. I have never experienced the extreme vacuum you are talking about. I would say if the motor is running great, is burning oil ans is not smoking excessively, then you are good to go.

 

[gw204]

It's probably pressure that you hear releasing. Those tanks get pressurized when the engine runs and that forces oil up to the engine mounted tank where the oil pump draws from. The caps have to be tight so there are no air leaks. Perfectly normal.


There is a small screen on the bottom of the oil pickup tube. Make sure those stay clear.

 

[River Rat]

Gw208,
You are correct. It was pressure. I opened the cap and the air was indeed escaping out, not being sucked in. Everything runs good and it is using oil so I guess all is ok.
Thanks for the feedback.