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Old 01-10-2018, 05:14 PM
bugsy63 bugsy63 is offline
Join Date: May 2010
Location: Melbourne, Australia
Posts: 59
Default High Fuel Pressures

Hi guys

I'm seeking advice regarding a "high fuel pressure" alarm and an indicated pressure of 46 PSI immediately after start up from idle to take-off power on my Dynon Skyview. I aborted the flight on seeing this.

I have an IO-320 with an Avstar injection servo.

Prior to this most extreme event, I have seen fuel pressures in the region of 38 to 39 PSI, which normalize to about 32 PSI after a few minutes of flight.

Operating the boost pump has no affect on the high readings

This and the Dynon forum suggest that the VDO sensors are susceptible to high readings, however, when priming with the Andair fuel pump prior to start, I see about 31 PSI, which would indicate to me that the sensor is functioning correctly.

I have not experienced any fluctuations in power output The issue seems to be related to the mechanical fuel pump. The fuel pump is not subject to the most recent Lycoming SB.

I understand that increased crankcase pressure could lead to this problem and will check the vent line, but I would like to hear of any other thoughts

Thank you in anticipation
Michael Brooks
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Old 01-10-2018, 05:44 PM
YellowJacket RV9 YellowJacket RV9 is offline
Join Date: Oct 2012
Location: Clearwater, FL / KZPH
Posts: 1,147

I had a mechanical fuel pump fail to high pressure, albeit it was the low pressure pump for a carbureted engine. However I believe the pump is the same with the exception of a spring. Replaced the pump with a new Tempest unit from ACS and pressures have been perfect. If you can rule out sensor and other simple fixes, you may just need a new fuel pump. I had heard they can't fail high, but I am not the only one who has experienced it. There are some good tips on VAF regarding installation, which is is rather straightforward but requires care.

Chris Johnson
RV-9A - Done(ish) 4/5/16! Flying 4/7/16

Last edited by YellowJacket RV9 : 01-10-2018 at 05:47 PM.
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Old 01-11-2018, 11:49 AM
TS Flightlines TS Flightlines is offline
Join Date: Apr 2010
Location: Ridgeland, SC
Posts: 2,166
Default Michael-

as with most off of these crazy readings, its suggested that the readings be verified with a known good mechanical gauge. Probably a sender or sender ground issue, but instead of chasing a ghost, test it.

Tom Swearengen, TS Flightlines LLC
Teflon Hose Assemblies for Experimentals
Proud Vendor for RV1, Donator to VAF
RV7 Tail Kit Completed, Fuse started-Pay as I go Plan
Ridgeland, SC
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Old 01-11-2018, 12:00 PM
alpinelakespilot2000 alpinelakespilot2000 is offline
Join Date: Jan 2005
Posts: 3,491

I had this issue with my carb'd engine. The issue with the VDO sensors is that they are flakey. Sometimes they will read perfectly and sometimes they would read erratically. Was difficult to pin down a cause, though periodic (at least annual) bleeding the fuel lines all the way up at the sensor seemed to make them read more consistently; poor ground or other connections might have caused it as well. Whatever, I moved to the three wire sensors and have not had any issues. That's where I would start if I were you.
Steve M.
Ellensburg WA
RV-9 Flying, 0-320, Catto

Donation reminder: Jan. 2019
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Old 01-11-2018, 07:34 PM
rswalden's Avatar
rswalden rswalden is offline
Join Date: Mar 2005
Posts: 81

Originally Posted by bugsy63 View Post
Hi guys

I'm seeking advice regarding a "high fuel pressure" alarm and an indicated pressure of 46 PSI immediately after start up from idle to take-off power on my Dynon Skyview. I aborted the flight on seeing this....

Simple fix.
You are probably using the standard single terminal fuel & oil pressure sensors by Van's. They are prone to failure after a while. It's unlikely you actually have HIGH fuel pressure. The same thing happened to me with my Skyview system during does get your attention.

Just replace your fuel pressure sensure with a solid state Kavlico sensor. You'll have to run an extra +5 volt line to the sensor from your Dynon. While you're at it: replace the oil pressure sensor too. Easy to install. Aircraft Spruce and Dynon carry the sensors.... and I believe they are standard now for Skyview systems. For fuel pressure sensors, there are two types available depending on whether you use fuel injection or not.
Bob Walden (Waldo), CFII-ASMEL
KFFC "Falcon RV Squadron" Peachtree City, GA
RV-7A Tip-Up, IO-390, 450+ Hours
RV-12 (Sold)... RV-12 Transition Training
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