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

[David Allen]

  Steve, thanks for the real story on this!  On my recalibrated systems I 
bet the backup fuel device calibration would be so far off it would not even 
run.
  Later,
David

---------

>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