GM Fuel Pump control scheme

[ae2598 at wayne.edu]

I guess that's why the car will still run if you disconnect the oil
pressure switch!  I've seen more than one S-10 4-cyl. switch fail and leak
profusely, it happened to mine a few years ago and it was late at night so
all I could find was a pipe plug to plug the oil passage.  truck ran fine
with the wiring harness dangling..

 On Sat, 27 Jan 2001, Shannen Durphey wrote:

> Another advantage to having a parallel control scheme is redundancy. 
> Relays also tend to get "burned" due to arcing across the contact points
> as they open and close.   This causes a poor electrical connection.  The
> oil pressure switch will still allow the pump to operate if this happens.  
> 
> In some trucks, the relay is used to circulate fuel for an extended time
> after the vehicle is shut off.  This helps prevent vapor formation in the
> lines as the engine hot soaks, and aids in hot restarts.  
> 
> Throttle body systems don't often show signs of bad relays, in my
> experience.  High pressure port injected fuel systems are more likely to. 
> In practice, the o.p. switch is not necessary.  I've run my converted 55
> chevy since 95 or 96 without an oil pressure switch.  But there's a wire
> to the pump conveniently located next to a wire from the battery, just in
> case something happens.
> Shannen
> 
> Bob Wooten wrote:
> > 
> > This is what i thought but then it can be said that if the CPU is
> > controlling the fuel pump, it certainly knows if the engine is running or
> > not & can turn off the pump.  I always thought that the oil pressure switch
> > was in series with the fuel pump relay for the shut down & that the relay
> > gets its power from the Ign. switch but i just checked the diagram in my
> > manual & that is not the case & they are certainly in parallel.
> > 
> > limp home mode sounds most plausible to me, but how does it get the motor
> > started?  no oil pressure no fuel, no fuel no oil pressure.
> > 
> > BW
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