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  #1  
Old 02-20-2008, 11:03 AM
Texholdem
 
Join Date: Mar 2007
Location: Dallas
Posts: 756
Is my purge switchover valve dead ?

the purge switchover valve located directly behind the windshield washer fluid reservoir is supposed to be working when you hear it tick like a little drum, or when you hold it in the hand you should feel it pulsating.

In my case I hear nothing, using a screw driver "stethoscope" and fell no pulse holding it. Engine was started cold at trial.

Is it dead if yes what is the consequence? I read that the purge valve handles excess fuel vapor retained in charcoal canister. I got no CEL and am wondering if there is a code thrown without CEL.

Any input greatly appreciated.

__________________
1996 E320 since 1/16/08, 171K miles as of Feb 2011

---------------------------------------------------------
1989 300CE - R.I.P. Dec 29 2007
Other MBs (sold): 1992 300E-24 - 1979 350SLC - 1984 230E - 1990 300CE

Last edited by Texholdem; 03-05-2009 at 09:38 PM.
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  #2  
Old 02-20-2008, 12:44 PM
Texholdem
 
Join Date: Mar 2007
Location: Dallas
Posts: 756
Just connected a OBD II scanner and there is no code. Apparently the valve does not throw any code letting me further in doubt whether it should tick or not?
__________________
1996 E320 since 1/16/08, 171K miles as of Feb 2011

---------------------------------------------------------
1989 300CE - R.I.P. Dec 29 2007
Other MBs (sold): 1992 300E-24 - 1979 350SLC - 1984 230E - 1990 300CE
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  #3  
Old 02-20-2008, 02:49 PM
Registered User
 
Join Date: Aug 1999
Location: Florida / N.H.
Posts: 8,781
Purge regeneration system has criteria to engage.
If you have No registered emmissions code, then you can assume it to be working.

The required activation modes are 80C coolant temp input to HFM/SFI module, spec MAF air quanity , engine RPM ,and load factors.

The valve is activated in 3 distinct Htz signal formats of 5/10/20 htz. This is detemined by load factors from sensor mapping to HFM module and the difference in htz duration varies the amout of vac applied as required to vent the canister petro absorbsion from the gas tank vent system back to the throttle intake vac port.

If this device did not have a hertz control system, it would change the fuel/air mixture too radically for engine management to adapt and stall.
So it is open/closed from 5 to 20 htz .
They usually plug up with debries and can be cleaned with WD-40..
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  #4  
Old 02-20-2008, 03:02 PM
Texholdem
 
Join Date: Mar 2007
Location: Dallas
Posts: 756
Very informative! Thanks!
__________________
1996 E320 since 1/16/08, 171K miles as of Feb 2011

---------------------------------------------------------
1989 300CE - R.I.P. Dec 29 2007
Other MBs (sold): 1992 300E-24 - 1979 350SLC - 1984 230E - 1990 300CE
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