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High Oil Pressure proven

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2 weeks 4 days ago #20696 by StuD
High Oil Pressure proven was created by StuD
I have experienced a sudden, dramatic increase in oil pressure from one flight to the next start up 2 weeks later. Engine details: 912 ULS, 2007 model, 820 hours, SN 5649712. Normal pressure is 43 psi and steady since new. Suddenly on cold start it went to 100 psi. Warming at idle of 2200 rpm it dropped to 78 psi. When warmed up, pushing the throttle up above 2700 rpm caused a sudden pressure drop to 68 psi. When down throttled below 2700 rpm there is a sudden increase to 78 psi. This has been relatively consistent throughout the following steps that I have taken presented in chronological order. Conventional wisdom is that "It's always the VDO gauge or a bad ground." So I put in a new gauge and checked the wiring. I replaced the old style pressure relief valve bolt and spring with the new version but not the ball which looked good. There was some wear on the old spring where the ball has sat for 820 hours. There is no shim below the spring. No change in pressure results so I installed a mechanical gauge and this confirmed that the high pressure was real. I did an oil and filter change and examined the magnetic plug which was almost spotless. I have sent an oil specimen for analysis but won't get the results soon. I have not opened the old oil filter yet for examination of the filter media. The 5 year rubber replacement has been followed with this engine. Something clearly happened but I am at a loss as to how I should proceed.

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2 weeks 4 days ago - 2 weeks 3 days ago #20699 by Bill Hertzel
Replied by Bill Hertzel on topic High Oil Pressure proven
Lets assume the Regulator is blocked.
The total amount of oil pumped by the engine will be force throug the bearings resultin in very high Oil Pressure. As you throttle up the bearing will accept more oil and the pressure will drop. Opposite of normal operation.

Assuming your oil Pressure sender is mounted on the Oil Pump in the ports on the side Opposite the Oil Filter...
Contrary to appearances, these ports are in the oil path After passing through the complete engine.
This rules out the Oil Filter blocking the flow.

The pressure regulator path is actually extremely short.
Oil passes through the Gerotor in the main Pump housing.
It then flows through Oil filter and passes over the temperature sensor before entering the engine.
Just below the Temp sensor is the Pressure Regulator.
Oil flows downward pushing the ball against the spring that controls the pressure.
Any oil that is bypassed returns directly back the Gerotor input section to be repumped.
Under normal operation, a lot of oil just goes around in a small circle getting filtered many times.

If the bypassed oil is restricted from returning to the pumping section, the pressure will be elevated.

Preliminary Test...
Run the engine for 30 seconds to confirm the Oil lines are fully Primed and Oil Pressure is registering.
Remove the Oil Pressure Regulator Ball and spring from the Pump.
Reinstall the Plug screw.
Start the engine again for 5 seconds MAX!
Observe that there is absolutely ZERO Oil Pressure.
If any Oil pressure is observed, there is a blockage.

If there was ZERO Oil Pressure, the Ball and Spring have a problem.
Replace both just for good measure.

Troubleshooting...
Remover the Oil Line to the Oil Pump
Remove the Oil Temperature Sender next to the Oil Filter.
Remove the Oil Filter.
Remove the Oil Regulator Ball and Spring.

Remove the Oil Pump Assembly from the engine. (4screws)
Keep the cover in place as you do this.
Note that there are 1 Large and 2 Smaller O-Rings on the Back of the pump

On a clean bench, remove the oil Pump Cover.
Lift out the Gerotor. (The circular gear looking parts)
Note that each part has a small drill spot facing you.
Pay Attention! The pin that drives the Gerotor is loosely fit and may fall out.

Using a 6-inch length of plastic or insulated wire not larger than 1/4" in diameter...

Insert the wire up through the Oil Pressure Regulator Chamber.
It should pass freely to and appear in the Temperature Sender port.

Insert the wire through the Oil Input port.
It should pass completely and freely through the pump and appear in the Oil Regulator Chamber.
Look carefully, it will not be in the center but offset towards the front edge.

If you encounter any blockage, Problem solved!

When reassembling, pay attention to the O-Rings, Drill Spots, and the Drive Pin.
Hand Prop the engine until you see Oil Pressure register on the gauge.
If No Oil pressure appears after 50 turns of the prop, an Oil Purge procedure may be needed.
Last edit: 2 weeks 3 days ago by Bill Hertzel.
The following user(s) said Thank You: RobSeaton

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1 week 3 days ago #20750 by StuD
Replied by StuD on topic High Oil Pressure proven
Thank you Bill for your detailed explanation. I am proceeding slowly and cautiously. I have received the results of the oil analysis and, as expected, everything was in the normal ranges. I am awaiting delivery of a new ball as well as a mushroom/bullet before starting your test procedure and will, at minimum replace the old ball although I am sceptical that this will have any effect. I have a question concerning hand propping the engine. I assume that this is done with the top spark plugs out in order to allow the prop to spin more easily. Is that correct?
I will keep the list informed of my progress on this issue since it seems to be rather unique.

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1 week 2 days ago - 1 week 2 days ago #20760 by Bill Hertzel
Replied by Bill Hertzel on topic High Oil Pressure proven
Remember that the engine has a Dry Sump.
If you remove the plugs, it will be easier to hand prop, but none of the oIl will be returned to the Oil Tank.
50 turns will move about a half of a Liter into the engine Oil Pan.
You would then have to re-insert the plugs(Don't forget to reapply the Heatsink Compound) and then turn it another dozen or so turns to "Burp" the Oil Tank.
Don't make it harder than it is.

50 turns is the point where you should give up as it is never going to happen and need to resort to the "Purge" Procedure.
If the prime was not totally lost, 10-20 turns will be all that is needed to confirm Oil Pressure. Maybe less.
This is far more likely.

When Hand propping, try to muster about One rev per second, 50-60 rpm.
A recently run engine will show pressure in less than 10 seconds.
Plus, it is a good aerobic exercise. ;)

I also forgot to mention...
When you take the hose off the Oil Pump Input port, the entire Oil Tank may want to drain out.
Be prepared to plug the hose, or catch 4 quarts of Oil.
If you plug the hose, you will not lose the prime.
If you drained the Oil Tank, after refilling the Oil Tank, loosening the Oil Hose at the pump input until it starts to leak oil is an alternate way to refill the hose and avoid doing a full "Purge" Procedure.
Last edit: 1 week 2 days ago by Bill Hertzel.

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3 days 3 hours ago #20830 by StuD
Replied by StuD on topic High Oil Pressure proven
Thanks again Bill for your assistance.
I have been unable to get the plane out for your test due to inclement weather and now winter has arrived further complicating life since I fly from a private field (which I wish I owned) with restrictions on snow removal.
Trying to move forward with this issue, I have:
1) Hand propped the engine and was able to get to 60 psi on a cold engine at 32F.
2) Removed the ball and spring and got 0 psi hand propping
3) Replaced ball and spring, pulled the electronic module plugs (upgraded new style ASM) to prevent starting and ran on the starter for two 10 second intervals getting 60 psi.
4) Pulled the ball and spring and ran on starter for 10 sec getting 0 psi.
This all inside the hangar on a gravel floor, no other planes present.
Do you think this is an adequate test for a blockage in the pressure regulator?

Stu

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2 days 12 hours ago - 19 hours 28 minutes ago #20836 by Bill Hertzel
Replied by Bill Hertzel on topic High Oil Pressure proven
Everything you just reported is completely normal.
Probably no blockage, or you may have cleared the problem without seeing it.
You will know when you actually start it again.

Is there any chance you have the wrong spring in it? (Not likely, but covering all bases.)
Any chance the spring or the Plug Screw have developed a burr preventing the spring from compressing properly?
It is getting time to start to look at the improbable.

Second thoughts...
When the mechanical gauge was installed was the needle Rock Steady?
Did it show any flutter?
Last edit: 19 hours 28 minutes ago by Bill Hertzel.

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