REFLECTOR: Odd fuel pressure Problem

[Jack Sheehan]

Scott,
Here is what I understand. The VM-1000 is a really good instrument. 
there have been a lot of installation problems but the readings you 
get from the instrument are correct usually. I have had the same 
problem with a Lycoming IO-540. It seems that the lycoming fuel pumps 
do actually fluctuate in pressure. The tolerance on the alarm of the 
VM-1000 sometimes does not trip but sometimes it does. Visionmicro 
does have a new software change that permits the delay of the alarm. 
They also have a recommended fix for the fuel pressure. They 
recommend the installation of a snubber in the pressure line just 
before the transducer similar to the one that is in front of the 
manifold pressure transducer. For some reason I can almost predict 
the low fuel pressure alarm as I climb through 8500 feet.
Seems the digital instruments are telling us things we really didn't 
want to know and would never see in an old analog gauge.
If you need more info I suggest you call Visionmicro systems. ask for 
Dave he is a really helpful technical support guy.
We used to have to make a decision between JPI or Visionmicro for a 
good digital system but now they are the same company or at least 
there has been some sort of merger but VisionMicro is still the place 
to call.
Why it took so long to happen on your airplane I do not know but I 
can also go for weeks without any fluctuation alarms which also does 
not make a lot of sense. I suppose temperature,pressure etc make a 
difference.

Jack
N55XL