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912 Oil Pressure

dwbuckeye

Member
We had a sending unit failure on our RV12, replaced it and changed the oil at the same time. Now we are only getting oil pressure into the yellow zone on the Dynon. Our mechanic is confidant everything is set up right, but doesn't have an idea why the pressure is reading low. Any ideas out there? The engine sounds perfectly smooth and we have run it up to proper oil temp to run it at 4000 RPM - but still no readings in the green.
 
I think the first thing I would suggest is to place a mechanical pressure gauge on the oil line so you can actually verify that the oil pressure sensor is really reading low.

If the pressure sensor is actually reading low, would check the wiring and if that checks out OK ... must be a faulty sensor.
 
pressure?

What is the actual pressure value showing on the gauge? (need more data than green or yellow)

Agree that a mechanical gauge could be used to verify the pressure per the above post. Another easier and safer way (no need to run engine) to check the sender is to remove the new oil pressure sender from the engine (but have the wiring connected) and hook it up to a compressed air source. Vary the compressed air from zero to 100 psi referencing the gauge on the air compressor and compare the corresponding efis oil pressure value.

Also check that the correct oil has been used. Rotax approved is Aeroshell Sport Plus 4. And that the oil intake system was purged of air, normally this is not required if the oil cooler has not been drained.

The mechanic could also check the oil pressure regulator spring and ball/plunger. There is a hex head plug under the oil pump housing near the oil filter. Be careful to not strip the fine thread when re-assembling. I don't think this will be the cause of low pressure unless the spring has failed or it has become jammed open.
 
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You might also need to check your pressure relief valve. Do a search here about mushroom head oil relief valves. I believe Cammie Patch was the author.
 
912 oil pressure

You might check with Dynon, i changed my fuel pressure sender and had to update HDX to include new part number. Now pressure indicates correctly, just a thought
 
Thanks all. We did install a mechanical pressure gauge and the oil pressure is perfect. Rotax suggested we got a faulty sending unit, and sent us another one. Same issue. Must be something with the Dynon interface. Our mechanic is having problems getting good support from Dynon about this.

Until we can get resolution, our mechanic installed a automotive oil pressure gauge. The only issue with that is that the Hobbs meter doesn't work. (which - for the members of our flying club....is the best news EVER! :)
 
Dave,
Reference the new sender from Dynon, is it a Kavilco 103757, and about $129?
Also did it have 2 or 3 wires from the sender?
Mine, which is the original, was relocated from the front of the engine to the firewall from the beginning. What I see in the KAI is there were 3 wires and the black wire was cut and heat shrinked. The remaining white and red wires had spade connectors installed and connected to corresponding wires going through the firewall.
I disconnected, cleaned, and reconnected the spade connectors but the pressure readings are still irregular. So I’m considering a new sender.
What I’m seeing to on initial cold start up it’s at 72 then settles down to around 55 but on run up at 52 with only rise to 53-54. I haven’t tried a mechanical gauge so I’m going to see if I can hunt one up around the airport.
 
We had a sending unit failure on our RV12, replaced it and changed the oil at the same time. Now we are only getting oil pressure into the yellow zone on the Dynon. <snip>

If your engine is a 912iS Sport, potential for reduced oil pressure readings is a known issue and is caused by a design change in porting; the oil pressure sender on the ULS receives filtered oil (located just 'after' the oil filter) and on the iS the sender receives unfiltered oil (located just 'before' the oil filter). The fix is straightforward; remove oil pump and clean the screen. Recommend contacting Dean at Lockwood for details.
 
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I disconnected, cleaned, and reconnected the spade connectors but the pressure readings are still irregular. So I’m considering a new sender.
What I’m seeing to on initial cold start up it’s at 72 then settles down to around 55 but on run up at 52 with only rise to 53-54. I haven’t tried a mechanical gauge so I’m going to see if I can hunt one up around the airport.

Those pressures are within spec for Rotax 912ULS:
Minimum: 12 psi (below 3500 rpm)
Normal: 29-73 psi
Max: 102 psi

My oil pressure is also higher on start up, typically 70-78 psi. Once the oil warms up the pressure is steady and in the range 55-60 psi depending on RPM.

If the oil pressure is fluctuating at a constant RPM then this can be caused by the pressure regulator ball and spring. There is an optional regulator cone part number 857-230 that replaces the ball and gives steadier pressure.

There is also a shim available (part number 227-055) to increase the compression of the spring and raise the pressure by a few psi.
 
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Thanks Paul
And yes those numbers are considered within specs so I’m going to continue to monitor but I guess since I’ve been focusing on the oil pressure I was concerned when I didn’t see a rise, or much of a rise, moving from low RPM to run up.

Also have had another person mention the replacement of the ball with the mushroom(cone) on the pressure regulator spring. Didn’t know about the shim so thanks for the information.
 
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According to my notes, 3.2 volts on Dynon D-180 EMS Pin 6 = 30psi.
Disconnect the wht/yel wire from the oil pressure sender and connect it to
3.2 volts positive (two flashlight batteries in series). Connect the negative
side of the 3.2 volts to ground.
 
Oil Pressure Sensor

check to be sure you have an exact replacement. A quick check on-line indicates that this sensor was changed on newer Rotax 912 engines. Perhaps you have a newer style sensor that is not compatible with the Dynon EMS. Dynon can probably also provide some guidance. I have had newer fuel sensors on the 912 not work correctly with the EMS.
 
Mine has always sat in the middle of the green band at about 50 psi +/-5 except when my oil pressure sensor went belly up.
 
washer could help

Rotax states in there HeavyMaintenanceManual concerning Lubrication that 'washer under the spring/ball combination is only needed when after changing [items] a low oil pressure is found'
So: a washer might solve your problems. Sound logic, too?
 
I have the Honeywell transmitter installed on the oil pump housing, I've been through 3 so far in about 400 hours so I bought a remote mount kit and installed it on firewall plus switched to the cone style pressure relief. Better indication, less fluctuations.
 
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