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1. 11:24 PM - VDO erratic fuel pressure readings resolved (Vincent Himsl)
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| Subject: | VDO erratic fuel pressure readings resolved |
Hello=2C
This is followup to my inquiry about erratic high fuel pressure readings on
my Dynon supplied VDO fuel pressure sender.
To recap=2C I would have normal readings for about thirty minutes then my f
uel pressure would slowly creep up to 9 or 10 psi=2C then start bouncing ar
ound tripping my warning alarms (wakes you up quick).
I do not have fuel injection but in my archive and google search came acros
s those with the same problem only with higher PSI readings.
Well=2C skipping the "I did everything perfect part"=2C the VDO fuel pressu
re sensor comes from Dynon with mounting tabs already installed. You assume
as I that these tabs are a match for the aircraft quality slide on crimps.
They apparently are not.
I removed and tossed these tabs and used a standard crimp connector instead
(one with hole in it). Fuel pressure readings are now rock solid after two
hour flight. Keep the nut and washers for use with the standard crimp thou
gh (I think they're metric) and do not tighten too much as I/you don't know
if too tight will change the sensor resistance.
In my troubleshooting odyssey I used a scope meter (yes I got that desperat
e) to determine if any electronic device save the ignition was affecting th
e signal. The signal stayed rock solid. The radio would impress a millivolt
high frequency signal across the sensor but there was no affect on the vol
tage or displayed PSI.
My take on the problem is that the tab crimp interface due to the mismatch
would become intermittent when exposed to heat and/or vibration.
I relay all this to help others avert a very long=2C frustrating search. Fr
ustrating in that most of us won't fly with erratic fuel pressure readings.
Now on to my tachometer accuracy problem.
Vinch H.
RV-8 'Flying'
N8432 - 24 hours
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