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Lycoming oil pressure indications

BenPoff

Member
I've been searching the VAF "database" - which is wonderful BTW - for advice on this subject of determining the causes and solutions to out of spec oil pressures. My particular problem is an EFIS/EIS reading HIGH oil pressure. While I have plenty of data to use now to diagnose and solve my potential issues, there's been one thing that has caused me pause. In several different threads there is a common comment from multiple respondents: (seemingly nonchalantly stated) "...just hook up a MECHANICAL pressure gauge..." The thought of testing the actual oil pressure being generated by using a calibrated and known to be properly functioning device had occurred to me and so I called two shops where I live and both said they did not have such a device! Did I confuse them with my request? I don't have a mechanical pressure gauge and I am not really interested in buying one at this point. Sounds to me like this should be something any shop worth their spit would have and use on a regular basis. Am I crazy?
 
While checking with a temporary gauge is the right next step, I offer that if you do see a higher than normal oil pressure reading the most likely issue may be you connected you pressure sender to the wrong oil port on the accessory case.

Look at the Lycoming manual - there is only one correct place to attach your oil sender line.

Carl
 
Spring

IIRC, there’s a spring that can be changed /adjusted that relates to oil pressure on the top right rear of the engine case??
 
Questions.

Is your engine new ?

How warm are the surroundings ?

Is this just on start up and warm up ?


New Lycomings do run with high pressure, I see you are in rainy Florida, so I guess it isn't too cold - another cause.

We would regularly see high pressure on and after start, but give it a few minutes and it settles. Then fly and it pops back to around 70 where it should be in flight.

In colder climbs it is not unusual to have to sit at low rpm for 20 mins to get it to come down.
 
While checking with a temporary gauge is the right next step, I offer that if you do see a higher than normal oil pressure reading the most likely issue may be you connected you pressure sender to the wrong oil port on the accessory case.

Look at the Lycoming manual - there is only one correct place to attach your oil sender line.

Carl
That is not correct. Lycoming powered Cessnas have been using front of right side oil gallery for years. The pressure there will be 8-10 psi less than at rear of engine
 
Thank you all for your input. I didn't spell out many of the other pertinent parameters for the high pressure indication as I had already pretty much had my questions answered from previous threads on the subject. My only comment requesting input on was the local full service repair shops telling me they didn't have an available mechanical pressure gauge to help me be sure with a quick ground run-up that my engine is healthy and I could concentrate on the issues my EIS sending unit may have, which is the most likely scenario in this case. I use these shops regularly, have never argued with them on their price for services and always payed them immediately, so there's no reason for them to shun me this service. I know many if not most of you are builders, but some of us are not and not A&Ps and are happy to get service done by our local shops. Doesn't mean I don't want to know how everything in my airplane works but at this time I'm not interested in buying a bunch of special tools. So if anyone who is like me and enjoys the heck out of flying their RV, but doesn't care quite so much to turn the wrench, would like to give feedback on their experience of what services a shop should and should not be expected to be able to provide, that was my question.
Thank you all again! I'm very happy to have this community sharing all the vast wealth of experiences it accumulates with each other!
 
High oil pressure

Hi,
Today I noticed high oil pressure , ususally its between 50 and 65 psi. But today I reached 82 psi . All other parameters normal .
Average CHT 160 ° celsius , egt 780 , oil T 77 .
That change in oil P doesnt smell good to me .
Is it a probe issue , or instrument calibration?
Oil consumption seems normal . Oil was changed 42 hours ago .
Looking at Lycoming documentation I found no limit indications for oil pressure .
 
Hi,
Today I noticed high oil pressure , ususally its between 50 and 65 psi. But today I reached 82 psi . All other parameters normal .
Average CHT 160 ° celsius , egt 780 , oil T 77 .
That change in oil P doesnt smell good to me .
Is it a probe issue , or instrument calibration?
Oil consumption seems normal . Oil was changed 42 hours ago .
Looking at Lycoming documentation I found no limit indications for oil pressure .

Trackdom,
Search other threads and you will find many answers to your questions. For addition specific replies to your inquiry, let everyone know the exact model engine you are using, what gauges/indicators/sensors you are using, and if you can provide any timeline data from a single flight to compare engine indications with phase of flight, especially engine RPM. You might consider starting your own thread to keep the conversation pertinent to your own issue as you work thru trouble-shooting.

From what I have learned so far, an oil pressure of 80psi is the sweet spot for most Lycoming engines. Low end during normal cruise power setting should be 60psi min. High end is different for different engines, but anything less than 90psi seems to be OK for O-320 and O-360 engines.
Indications that oil pressure is increasing above your engine's normal range with no apparent mechanical issues is usually going to be a sending unit/probe sensor failing, but not always! If possible, always try to determine your actual oil pressure with a calibrated mechanical gauge.
Hope this get's you started on your quest for more knowledge! Good luck!
 
My only comment requesting input on was the local full service repair shops telling me they didn't have an available mechanical pressure gauge to help me be sure with a quick ground run-up that my engine

Any round mechanical gauge with a reasonable pressure range will work and you only need a few fittings and a short hose from Spruce to put one together.

However, check the grounding of your oil pressure sensor and the EIS. If they are grounded at different points on the airframe it will cause ground loops and spurious readings.

The other day I had a high reading which was fine after I tapped on the regulator-ball housing. I guess the ball had hung up on a bit of carbon or something. I have had the ground loop problem before, too. Spent weeks trying to solve a fuel pressure problem which turned out to be a ground loop (in a pusher).
 
Hi Ben,
Thanks for your recommandations, that’s right I should begin a new thread and give more details to solve any issue .
 
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