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New High Oil Pressure Before Takeoff

ChuckGant

Well Known Member
We have an RV7 with an IO-360/CS Prop.
We are using Grand Rapids Horizon EX with the oil pressure warning alarm set to go off at 99 psi. The Lycoming manual says 115, but the highest setting allowed on the GRT is 99.

We always wait until oil temperature is above 75 degrees for run-ups and above 100 degrees for take-off and have never gotten high oil pressure warnings.

Just recently (in the last 2 weeks are so), with the weather in the 50s-60s, we are getting high oil pressure warnings when doing our run-ups, with the oil temperature above 100 degrees. Because of this, we have been letting the engine warm up to over 130 degrees before the oil pressure indicates down in the 80s at idle and under 99 at take-off. Once flying, the oil pressure remains in the mid-80s the entire flight. Oil temperatures in flight are running about 170-180 degrees.

Any ideas?

I'm thinking it is a pressure transducer problem, but I don't know enough to know what else would cause a change in oil pressure.

Thanks,
Chuck
 
Always handy to have a dumb oil pressure gauge from the local autoparts store handy for a first sanity check.
 
The most likely is is a pressure transducer or wiring problem. Test it based on Grand Rapids troubleshooting chart.

I run two oil pressure sources for this very reason......
 
When the oil temp is in the green, cycle the prop 3 or 4 times at 1800rpm, then bring it back to idle, wait, then back to 1000 - 1200 rpm. Sometimes the oil pressure relief valve sticks or the vernatherm sticks which short cycles the oil.

Ours does it sometimes but clears.
 
I had a bad oil pressure reading on my GRT EFIS / EIS awhile back and called GRT about. They said to try tapping on the transducer a few times with a screw driver handle or similar. No kidding. And better yet, it worked!

erich
 
Great ideas guys. I appreciate the input. May be a few days before I can get out there to try them out.
 
I had a bad oil pressure reading on my GRT EFIS / EIS awhile back and called GRT about. They said to try tapping on the transducer a few times with a screw driver handle or similar. No kidding. And better yet, it worked!

Interesting technique, think I?ll have to give that a try on my GRT fuel pressure sender. I?ve already replaced my oil pressure sender, but now my fuel sender is acting up... will try the hammer tap before ordering a new one. Is it just me or does it seem that the GRT (VDO?) senders are kinda junky?
 
I just bought a EIS today because the senders & probes are less expensive than the other guys , VDO have been around for a long time and I see their signature every time I start the Polaris ATV and the 25 year old Porsche
 
Oil or fuel pressure test

I always like to ?T? in a mechanical test gauge so that the normal installed transducer and gauge readings can be compared to the test gauge in real time.

Don Broussard
RV9 Rebuild in Progress
57 Pacer
 
The VDO sensors are known to gradually fail high (if they are going to fail - so I’d say it’s a better than even bet that is what you’re seeing. AS others have said - confirm with a mechanical gauge - or buy a new sender (the “throw money at it” philosophy) and see if that fixes it.

Paul
 
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