I had an isolator made by Autometer but was never able
to completely purge the air and get reliable readings. After multiple attempts I
finally gave up and deleted it. So I guess I may be on borrowed time before I
get the fuel leak. My history seems to be that if it can fail on my airplane it
will. If you identify something that works and is relatively small and
inexpensive please let us know.
Mike Wills
Sent: Saturday, April 10, 2010 2:34 PM
Subject: [FlyRotary] Re: Fuel Pressure sensor warning / crank sensor
mounts
Just got done doing a final flight test on the RV-8 before
Sun n Fun decision time. The battery had gone flat from being discharged
to zero too many times by the Blue Mountain EFIS. It draws some power even
when off. Replaced the battery yesterday with another Odessy 925 and the
engine turned over smartly.
Had just changed out the EC2 for an EC3
just because i felt the need to say I had personally flown it on a 20B.
Also made a new mount for the RX-8 crank sensor. I had been
getting an occasional high speed miss above 6200 rpm and suspected the
problem might be the same as a customer's Continental AC engine that was
equipped with an EC3. That turned out to be a resonant condition where the
mount would vibrate above a certain rpm causing the distance between sensor and
trigger wheel to vary enough to cause distortion of the signal. That
caused the EC3 to lose sync momentarily. Making a very rigid mount cured
the problem on the Cont. and my 20B. It's sweet at all rpms now.
This might have been the problem on Mark Steitle's 20B as well. We thought
it was the material it was made of but i'm not sure about that now. He
also replaced his mount and the problem went away. Anyway, if you make
your own crank sensor mount, make sure it is really rigid.
The RV-8 flew
perfectly on the test flight with only engine anomaly being a low fuel pressure
reading. I knew it was an instrument problem because the engine wouldn't
run if the fuel pressure was only 6 psi. Un-cowled the engine and heard a
hissing noise coming from the fuel pressure sensor. There was a steady
drip of fuel from the terminal end of the sensor. Why i didn't have
an engine fire in flight I don't know. SO, I can no longer
recommend using the VDO pressure sensors for use on fuel systems.
Either an isolator must be used or a sensor rated for fuel exposure be
installed. I've been using one on my -4 for >7 years with no problems.
About 3 years ago VDO started putting a sticker in the pressure sensor
package saying not to use them on fuel pressure applications. I suspect
they changed something in the manufacturing process. I'll do some research
on sensors and see if I can find a suitable replacement that doesn't cost a
fortune. Anyone have a lead on sensor isolators?
My
transponder also decided it wasn't going to work this time. I recently had
the instrument panel out for the EC3 change so I think it's an antenna connector
or coax problem.
Bummer. Too many last minute squawks to fix in
time so will have to take the RV-4 to SnF :-(
Tracy
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