[Gmecm] FW: Undignified death of a project :P

[Steve Ravet]

A note from JW regarding the fuel pump relay and oil pressure switch.
 
--steve

The Oil Pressure Switch that runs the fuel pump isn't about backing up
the Fuel Pump relay, which it does as a side benefit.  It is about the
Backup Fuel function of the older (pre early '90s) ECMs.  If the digital
core fails in these boxes, the distributor or DIS is put in BYPASS mode,
allowing the engine to run on the base spark, the Fuel Injectors are run
by the Backup Fuel Device in the ECM (analog fuel injection, what the
calibration resistors are for), and the Oil Pressure Switch runs the
pump.  The BFD was removed later when it became untenable to have
redundancy like this and confidence in the controllers increased.  It
would be cheaper to use a more reliable relay then add in a parallel
switch for the Fuel Pump. 

JW 

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