Oil pressure help needed!

[Derek1983]

This past weekend during the annual condition inspection we replaced The lines to the bottom mounted oil cooler due to age. Once those were installed removed 4 spark plugs and cranked the engine over with the starter for 20 seconds to purge the air from the lines. after a few seconds of cranking registered 22psi. Let it rest for a few minutes to cool the starter and repeated and got the same pressure reading. On the third time (realistically it didn’t need it but just for good measure). Oil pressure instantly shot up to 100psi, stopped cranking let it rest a few seconds repeated with the same results. Swapped the sender unit to a new one (Sonex VDO unit) and still got the same results.

Anyways pulled the airplane out of the hanger and fired it up, still was showing the same 100psi at 1000-1200rpm. After warming up some oil pressure dropped to 85-90 at 1100rpm but was still 115-120 at a full throttle run. Gauge is a MGL blaze EMS

When I purchased this aircraft and flew it home the end of April had good pressure well within range the entire flight.  airplane hasn’t flown since then due to horrible spring weather and then doing a panel update

[GraemeSmith]

Same suggestion I gave on FB - check the two oil plunger/spring reliefs. You will find the location in the Aerovee manual. Sounds like a stuck plunger (lack of use/corrosion?)

[Derek1983]

Same suggestion I gave on FB - check the two oil plunger/spring reliefs. You will find the location in the Aerovee manual. Sounds like a stuck plunger (lack of use/corrosion?)

Lack of use for sure. Thought I’d throw it on here too :)

[mike.smith]

Since I've just gone through a low OP issue (finally solved) I'll add this to Graeme's response. The plungers sometimes get stuck (corrosion is a possibility). It should move freely in the channel. Using a telescoping magnet allows you to both push and pull the two plungers. If one or both don't move freely, you can use some emery cloth to polish (not grind) the plungers. You can wrap some emery paper around a wood dowel and turn it inside the plunger chambers to smooth them out, too. I had to do both of those to my engine the first time I built it. After that, no problems.

You could order new plungers/springs just in case. The problem with trouble shooting anything at the bottom of the engine is you have to drain and refill the oil every time! Gets expensive.

Make sure the oil lines are connected properly, and make sure neither are blocked with something. That's when the issue started, so that's the first place to check.

You might also check that the oil crankcase breather is not blocked.

At your next condition inspection, consider changing to a top-mounted oil cooler. Less plumbing, less possible points of failure, and makes working under the engine much easier. Also, if you don't have a quick-drain in the sump plate, consider that, too. Put a plastic hose on the valve and drain the oil easy-peazy.