Grounds, Shielding, etc...

[Grant Beattie]

I need your expert advice on how to best shield electronics from
noise/vibration generated in a vehicle so that the electronics can do it's
job best.  I'm partway into a data acquisition system (for a kart) and the
system has it's own internal battery.  Should my cpu "box" be grounded to
the chassis of the vehicle or should it be isolated?  Should various
sensors have metal shielding around their cabling? 

One example I can give you is that I have a magnet and hall sensor on the 
rear (solid for karts) axle.  This requires me to run +5v, Gnd and signal 
about 3' from the CPU to the sensor.  I'm using a cable which has a 
ground shield and two inner conductors on which I'm placing +5v and 
signal.  There is no connection whatsoever between this ground and the 
chassis.  Is this good or evil?

For what it's worth my preliminary tests were less than stunning with the 
CPU resetting itself intermittently.  For the time being I had housed it 
in an unshielded plastic case and I think the ignition noise from the 
heathen Briggs 5hp motor overwhelmed it.

Any ideas?
GB