flyrotary@lancaironline.net Mailing List Archive

Tracy;

I’m glad you mentioned that. I was about to conclude that the problem was incorrect data, not faulty regulator. I could not be sure that the richer mixture I had connected with the first occurrence of higher fuel pressure was cause and effect – I possible had not leaned again after climbing to a higher altitude – then noticed the mixture and the higher pressure reading. On the second occurrence I had not noted a mixture change. Flew for an hour today (beautiful up and down the beachJ) and the fuel pressure was always where it should be. The sensor offset was also what it should be. So until it happens again . .

Are you going to replace the VDO sender?

Al G

-----Original Message-----
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Tracy Crook
Sent: Saturday, August 09, 2008 3:57 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Fuel pressure

I am seeing some similar indications on fuel pressure (going higher) myself but not a change in mixture.

I looked at the sensor offset in EM2 after landing (and relieving the pressure in fuel system) and it looks like the sensor is drifting around. I reset the sensor offset and things went back to normal for awhile.

VDO now has a warning on their senders to not use them on anything but oil. Don't know if this has anything to do with it or not. My sender is about 6 years old.

Tracy

On Sat, Aug 9, 2008 at 3:32 PM, Al Gietzen <ALVentures@cox.net> wrote:

Somewhere during my trip a few weeks ago, I had noted that the engine seemes to be running a bit rich from where I had set it. I then noted that the fuel pressure was reading high – like about 48 -49 psi; and I have the regulator set for 40 psi at WOT. Not know what else to try, I switched from pump 1 to pump 2. After a bit the pressure was back to normal; and worked fine after that.

My thought later was that switching the pumps should have nothing to do with it. The two pumps are in parallel, then the filter, then the pressure sensor, then the fuel rail with the regulator on the end, bypassing back to the tank.

Last week on a short flight I noted the fuel pressure bar on the EM2 at the max and blinking. The readout was 50 psi. I watched for a short while nothing changed; then switched pumps. Nothing changed right away, but the pressure slowly returned to normal. Then running pump1, both pumps, or pump 2 didn't make any difference.

I discussed with the expert at TWM (the maker of the pressure regulator) and after some discussion, he was completely at a loss as to what could cause the pressure regulator to act in that fashion. It is a MAP referenced regulator, and the MAP readout was as it should be.

I'm baffled.