REFLECTOR: Odd fuel pressure Problem

[Brian Michalk]

This is a digital instrument.  It has a shortcoming that analog gauges do
not have; it must sample the signal.  Scott, I'm sure you are aware of the
Nyquist limit, but others here may not.  Basically Nyquist says that you
must sample a signal at twice the highest possible frequency that may be
present in the signal you are sampling.  This can be applied to noise (for
aliasing), and for data resolution, like how many pixels does it take to
resolve an object, or how high of a frequency is required to represent
something.

Anyway, the Vision Micro must sample the signal, and it should have a
bandpass filter before the sampling circuit so that noise over a certain
frequency can't be aliased onto the resulting data.
If this is the problem, which doesn't sound like the case here, I would look
at a couple of things.

1) Does the Vision Micro sample the fuel pressure at some rate near engine
RPM?  Does the fuel pump cause pressure pulses in this range?
2) has something changed where the signal line now has spikes on it that
possibly change with engine RPM?  This relates to the previous point.
3) Has something damaged the bandpass filter?  This one is a bit of a reach.

 Brian Michalk  <http://www.michalk.com>
Life is what you make of it ... never wish you had done something.
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