EVAP canister help

[Len Sabatine]

     From what I've observer of properly functioning GM Systems , Yes. It's 
especially
     obvious when the fuel level becomes low , thereby allowing 
increased  free volume
     in the fuel tank. Remember , the basic idea of the purge system is to 
cycle evap
     fuel component back into the main fuel storage for reuse. It's a 
pressure and Vacuum
     System, depending upon which "mode " it's operating . OBD2 Systems 
actually Monitor
     actual Fuel Tank pressure conditions and the PCM responds accordingly. 
BTW , when
     the EVAP works correctly , cylinder walls and valve guides tend to 
live longer. Less
     fuel dilution to Engine Lubricant as well. GM service manuals go into 
detail of the EVAP
     system.
     Len

>Hello,
>
>Are you saying that if I have that system I should always notice a pressue 
>when I
>open the cap?
>
>Louis
>
>Len Sabatine wrote:
>
> >      Sys should pass a vacuum, pressure test. Supply tube solder joints on
> > fuel pickup
> >      assembly are often suspect. Sleepy purge valve , gas cap , filler neck
> > leak
> >      being some other problems. Zero leakage is minimum acceptable.
> >      Len
> >
> > >My last two gas station visits have shown that when I remove the gas cap
> > >from my 89 Formula 350, '165 absolutely NO "sucking" sound is 
> made.  It has
> > >done it before but it was only a quick fizz.  Does the tank run under a
> > >vacuum, therefore the sucking sounds when you crack the cap?  Does it take
> > >time for this condition to develop?  (In other words, start car, quick 
> drive
> > >to gas station, shut-off, typically no suck sound?)  Likely a bad gas cap?
> > >Bad vac line?  Bad canister?
> > >
> > >I know my 87 T/A 305CCC was quite obnoxious when the gas cap was removed.
> > >I'm wondering if this is the cause of my laxluster gas mileage even BEFORE
> > >the motor was rebuilt.  Any ideas on how to test?
> > >
> > >Steve
> > >----------------------------------------------------------------------- 
> -----
> > >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
>
>----------------------------------------------------------------------------
>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