Rotax 912 80hp no oil pressure after oil change

I like to do a full oil/air purge, every time I change my oil/filter. May not be necessary but it gives me piece of mind, that there is no air in the system that may be restricting circulation.

Hi Mike,

Yes you should have had oil pressure. For the moment this doesn’t sound like a real oil pressure issue. If I have something like this or a weird gauge reading I put on a separate mechanical gauge to compare. You can go to the hardware store and buy a brass fitting to install down at the oil inlet at the pump. Then I run a small copper flexible tube up to the top of the engine. Small inside diameter tube.  Then I put  a tee fitting in line there. Here I hook up the original panel instrument hose and on the other tee fitting side a mechanical gauge. I leave the mechanical gauge slightly lose at start until I get a couple drips of oil to make sure my line is purged of air then tighten it.  Nw I get to compare readings. I’ve never had a real oil pressure issue. It’s usually the sending unit or the panel gauge or a bad wire.

This test is only for a ground run to test the system.

Hi Sean,

During an oil change you should have very little air introduction. This isn’t an issue. Plus I highly recommend

pre-filling the oil filter. I can fill an oil filter three times to the top and it won’t spill any on installation. The oil soaks into the filter medium and out into the outer part of the canister.  If you’re worried about air then just do a venting by rotating the prop to help charge the filter more. A NORMAL oil change should not introduce enough air to require a full oil purging. The engine can handle a small amount of air.

Oil venting and an oil purge are different for those who don’t know.

My oil pressue comes up almost immediately when the engine starts. My starting checklist says to shut down the engine if no pressure is seen within 10 seconds. If it ran for 3 minutes with no indicated pressure and the engine sounded normal then I suspect you have a gauge or sender issue that you will discover with your multimeter. You could just unscrew the valve, leave it connected to the gauge, add a ground wire and pressurise it with a foot pump. You can then fault-find it from there.

Or install a wet line panel oil pressure gauge fed by a braided steel hose wrapped in fire sleeve (Down Sean! Down! Bad Sean! Bad!) 😀 and never worry about sending units or grounds or fabricating test wet lines or electrical anything ever again.