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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

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?)

GraemeSmith wrote: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 :)

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.

I am having the same exact problem. I replaced the sender with a new one with the same results. I put a direct pressure gauge on the engine and it shows 50PSI and the EIS indicates 100 PSI. I sent the EIS unit to GRT and it tested good. They sent me a loaner unit that uses the 0-80 PSI sender and had the same results. I used a calibrated dead weight tester so I would know the exact pressure, removed my EIS unit from the aircraft put it on a bench ran ground wires from the case of the unit, pin one and a wire from sender body to the neg battery post. Ran a wire from pin 5 to positive battery post, Ran a wire from the sender to pin 18 and bench tested the system without the aircraft being involved at all and I have the same high pressure indicated on the EIS throughout the pressure range. I am really at a loss here! The only thing that would make since is I have two senders with the exact same problem and booth of them are new. I am open to any suggestion.

Thanks,
Sid

Derek,
Did you ever find a resolution to this problem?

Thanks,
Sid

I'd remove the EIS from the picture and directly connect an ohmmeter to the VDO sender and confirm you get a range of resistances as pressure is varied and that it matches the spec for the sender. Connecting the sender to an air compressor might be a good way to verify this.

If that works, then I'd suspect the EIS settings are wrong or power isn't being applied to the sender through the correct resistance.

Just a follow up on my oil pressure issue, I bought the first sender from spruce during the initial build of the engine. During the first start the oil pressure was 100 psi. After verifying the pressure was actually 60 psi with a inline gauge I ordered a new sender again from Spruce And had the same exact problem. Thinking there is no way it would be the sender I took the plane apart checking all the wiring and found nothing. I ordered the 3rd sender from GRT and problem solved! Same P/N so I have no idea how it would make any difference where you buy it from but it did or just a fluke.

Sid