GM Fuel Pump control scheme

[Bruce Plecan]

It's goes back to KISS.
At the time it was first in common use (vega) it was a simple way to turn
off an electric fuel pump.  The engine run fuel pumps would generally stop
when inverted.   An electric pump would run till the battery faltered.  An
electric pump run dry in a enverted gas tank could generate an exposive
situtation.

If there is a next to 0 chance of the gas tank pump going critical inverted
then that would lessen the need for the one sinerio.

then from time to time GM just does things to do them.
Heck they could have had one code and and just clipped it together in a
module nature.  Instead they have at least 100 different masks.

Only the deepest of insiders would know all the whys.

IMO, they have soo much talent hidden there and yet children, are running
the store.
Oh well
rant and EFI theory at the General off
Bruce




> I have beenthining about this for a couple of days  & i am still confused.
> if this were in fact to kill the engine if the oil pressure dropped below
> the switch threshold & that the redundant CPU relay was just for starting,
> then this would make a lot of sense (kind of).  I would think that putting
> in a switch to tell the cpu OP OK or OP BAD would do the same thing.  the
> thing that i don't get is that my car does not have a OP switch & it has
> never had a problem with it running.  this tells me that the cpu must be
> turning on the FPS relay & keeping it on (& it is obviously not hot wired
> on as the CPU turns in on when i turn the key on & then turns it off until
> the motor is running).  this tells me that the OP switch is a completely
> redundant system.  the question is why.
>
> It does not make sense to me that the general would put this in because
the
> relays have a tendency to fail.  if that were the case then good
> engineering says that you spec a higher amp relay or put two of them in
> series with each other so that the cheaper less amperage relay can drive
> the coil of the power relay (kind of like a darlington pair or a
industrial
> controller).  one of the gents on the list suggested that this had to do
> with limp home mode & that does make some good sense.  If i am right the
> resistors & "stuff" on the memcal does something to the cpu to control
> injectors, the ign module does spark & the other thing has to be fuel.  I
> would think that there is a more high tech approach, but sometime
> simplicity is the best way to go.
>
> Am i thinkin' to hard?
> thanks for listening.
> BW
>
>
>
>
> <Snip>
>
>
>
> --- Bob Wooten
> --- r71chevy at earthlink.net
> --- www.r71camaro.homestead.com
>
>
>
> --------------------------------------------------------------------------
--
> To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
> in the body of a message (not the subject) to majordomo at lists.diy-efi.org
>

----------------------------------------------------------------------------
To unsubscribe from gmecm, send "unsubscribe gmecm" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org