High oil pressure

Yen · #1 08-31-2014, 12:49 AM

I have a high oil pressure problem. The Lycoming D2G had about 40 hours on when all of a sudden i noticed the pressure was over the red line. It had been perfectly good before this.
My first thought was that it could be a faulty guage, or sender. The electronic sender is in the top of the engine.
I have removed the oil pressure valve and it appeared to be perfectly good.
I poked a piece of plastic pipe down the opening from the relief valve to the sump and it felt as if I was touching solid metal, with no trace of any dirty oil when I removed it.
Running the engine I still have the high pressure. I unscrewed the adjustment in stages, as far as about 4 turns and still no change in the pressure. I don't want to go too far and get no pressure, and anyway as it was OK as set from the factory I cannot see that pressure should increase. As the pressure guage thread has developed a slight leak, I am tending to discount the faulty guage theory.
Does anyone know what is at the base of the return line? Is there a right angle bend?
It looks as if I will have to remove the sump, and I would like to avoid that.
Anyone have any ideas about what I should do?

drill_and_buck · #2 08-31-2014, 03:30 AM

Yen,
What type of oil pressure sender do you have? The early ones that Dynon were using were known to be problematic.

To troubleshoot you could install a pressure gague in line with your existing sensor to validate its accuracy. If the sensor was installed on a manifold there is most likely an extra port you can use to temporarily plumb in an oil pressure gague.

Paul K · #3 08-31-2014, 07:05 AM

I would also suggest you check the sensor. Your issue sounds just like my issue at about the same engine time. Ended up being a loose connection, spade type. I eliminated it and all has been good for the next 100 hrs or so.

Kent Ashton · #4 08-31-2014, 10:26 AM

Check for ground loops. If the sender and the gauge are grounded at different points, a difference in ground potential can induce a small current that gives bogus readings. Been there. There is almost no way to get high oil pressure on a Lycoming

RV7A Flyer · #5 08-31-2014, 04:02 PM

Quote:

Originally Posted by drill_and_buck

Yen,
What type of oil pressure sender do you have? The early ones that Dynon were using were known to be problematic.

To troubleshoot you could install a pressure gague in line with your existing sensor to validate its accuracy. If the sensor was installed on a manifold there is most likely an extra port you can use to temporarily plumb in an oil pressure gague.

Yep...mine started reading higher and higher after about 150 hours. Figuring that didn't make sense, I swapped it out for a new one (same style, though, VDO, so I didn't have to run more wire just yet). Worked fine for another 100 hours, but is now starting to show jitter in the signal.

Same issue with the fuel pressure sendor. Same solution, although it's still reading fine.

At annual, these pieces of junk are headed to the garbage can to be replaced by Kavlico senders.

Robert Anglin · #6 08-31-2014, 05:44 PM

If you look in most any old timers tool-box you will find a nice liquid filled boredon gage with a nice peace of hose on it with a 1/8" mail end. When we see a pressure that we don't like we screw the gage into the system and look at that figure. most of the time it is not a good idea to take an electric sending unit or gages word for being correct. The old liquid gage if calibrated will not lie. Just be nice to it and never drop it. Darn I am showing my gray hair again. Hope this helps, yours as always R.E.A. III #80888

AlexPeterson · #7 08-31-2014, 07:16 PM

Quote:

Originally Posted by Robert Anglin

If you look in most any old timers tool-box you will find a nice liquid filled boredon gage with a nice peace of hose on it with a 1/8" mail end. When we see a pressure that we don't like we screw the gage into the system and look at that figure. most of the time it is not a good idea to take an electric sending unit or gages word for being correct. The old liquid gage if calibrated will not lie. Just be nice to it and never drop it. Darn I am showing my gray hair again. Hope this helps, yours as always R.E.A. III #80888

I've suggested to many that one gauge that truly needs backing up is an electric oil pressure gauge. This is one example of where it would be worth the $100, or whatever they cost now, mechanical gauge.

The other scenario is when you are flying along, and the electronic gauge shows no oil pressure. What are you gonna do in that situation? Something to think about.

I've had a VDO sensor (fuel pressure) go flaky, and a MAP sensor also went TU. The little mechanical oil gauge chugs along.

Yen · #8 08-31-2014, 09:07 PM

I have to get back to the airstrip to further investigate, can't find a bourdon tube gauge here.
I have experienced a complete loss of oil pressure gauge in my Corby Starlet, headed back home, reduced power and hoped it was an electrical malfunction, which it was.
There was no oil in the area around the pressure relief valve, which in hindsight seems odd.

Yen · #9 09-02-2014, 11:20 PM

Today I put a bourdon tube gauge on the engine and the pressure is just where it should be, so I will be replacing the Van's gauge and sensor, also the oil temp gauge which fluctuates and tends to show high temps, although the oil is still perfectly good looking after about 23 hours. I will check for poor grounds first and see if there is any problem there.
Thanks for the help.