Karl-
     
     The low(er) pressure sender operates in a manner most resemblingthe 
     one we are all familiar with from our air cooled days.  It grounds out 
     when there's not enough pressure.
     
     My recommendation is to disconnect the wire at the sender to make sure 
     it's not a wiring/insulation problem.  Since the wire runs up and over 
     the #1 cylinder, there could be a bare spot that's touching there, 
     too.  Conceivably the sender could also be bad, or be plugged enough 
     for the pressure to be blocked.
     
     My understanding is that there were two types of HIGH pressure 
     senders, but just one of the low ones - double check this.
     
     -Blaine