GM Fuel Pump control scheme

[Dave Zug.]

Thru all this, I wondered why none of the HACS had a "pump prime time"
variable.

----- Original Message -----
From: Ludis Langens <ludis at cruzers.com>
To: <gmecm at diy-efi.org>
Sent: Monday, January 29, 2001 2:07 PM
Subject: Re: GM Fuel Pump control scheme


> WEG1192 at aol.com wrote:
> >
> > To me its obvious that Steve Ravet was right in that the OP switch is
used to
> > keep the pump running during CPU failure, otherwise limp home wouldn't
work
> > period. I can also say for certain that the ECM keeps the pump running
as
> > long it recieves ignition pulses from the distributor. [...]
> > The only plausible resaon left is to keep the pump running during
> > limp home mode.
>
> One problem with your theory - the fuel pump relay is controlled 100% of
> the time by the limp home circuit.  The CPU (and PROM) need to do
> nothing to operate the fuel pump relay.  In fact, they can't control the
relay.
>
> When initially powered up, the limp home circuit turns on the relay
> briefly, and again whenever there is a distributor reference pulse.
>
> --
> Ludis Langens                               ludis (at) cruzers (dot) com
> Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/
>
>
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