Fluctuating oil pressure

[bipbuilder]

I have aerovee non turbo. Has almost 40 hours. Oil pressure has been about 48 psi the first 20 hours. One flight it would go from 48 down to 35 then back to 48. It did this continuously and would take about 10 seconds per cycle. Removed oil screen and oil pump cover to check condition. Both were in good shape. I then checked pressure relief plungers. Both fell out with a tap on the block. Neither had any scratches, debris, or burnt oil residue. I changed oil, reassembled and flew it. Problem now gone. 15 hours later problem is back. I am thinking the pressure relief plungers need smoothed with emery cloth.
Oil temp is 170, cylinder Temps about 325. At idle it now runs about 25 psi. It was running close to 50. I'm thinking the relief plungers or springs have to be the problem.

[tpeppers]

Did you check the oil pressure sender?

[pappas]

If your O/P sender is screwed into the top of the block, and you used some type of thread sealant for the 1/8 inch NPT threads, you may have an intermittent grounding situation. If you have the VDO sender, run a ground wire to it. If you have a Kavlico, it has a ground wire so just make sure it is secure.

It could be something else, but you need to start with a correctly functioning sender.

[bipbuilder]

Forgot to mention, I have seen to many vdo problems and put a mechanical guage in it

[skyrangernz]

Fixed my oil pressure problems by fitting a direct reading oil gauge from the local auto parts dealer.

[bipbuilder]

Pulled oil pressure relief spring out and the front valve fell out. Went to the rear of the engine and removed the spring. The valve stayed in place. Took a little persuasion with a stick to get it out. Used emery cloth on it and reinstalled it. Test flew and oil pressure was a little lower at about 45, but no fluctuation. I think problem found.

[Spaceman]

If you remove the pressure relief plungers when the engine is full of oil, will all the oil drain out from that spot? Or can you check them without making much of a mess?

[bipbuilder]

Only the one at the back leaked a little out.

[pappas]

If I raise the tail of my Waiex to level flight attitude, the rear oil passage does not leak.

[Bryan Cotton]

If I raise the tail of my Waiex to level flight attitude, the rear oil passage does not leak.

Many thanks for both the question and answer. This job is in my future.