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Externally Adjustable Primary Pressure Regulator

 
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Rasta Monsta  



Joined: 12 Jul 2006
Posts: 11727
Location: PacNW

PostPosted: Sat Aug 02, 2008 3:16 am    Post subject: Externally Adjustable Primary Pressure Regulator Reply with quote

I noticed this some time ago and have been meaning to toss up a pic for discussion.



Anyone ever seen this setup before?
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  • WeiBe (1987 924S 2.5t) - 931 S3
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dpw928  



Joined: 02 Nov 2002
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Location: owasso, ok 74055

PostPosted: Sat Aug 02, 2008 4:09 am    Post subject: Reply with quote

Never seen it before but it would save a lot of time and fumbling with spacers. Is that from a later VW or MB?

Dennis
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Smoothie  



Joined: 01 Jan 2003
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Location: DE (the one near MD, PA, NJ)

PostPosted: Sat Aug 02, 2008 5:01 am    Post subject: Reply with quote

Mine has that - it isn't an external adjustment. I think any FD with the "push-up" valve (which closes off [return flow] and pressure loss through the WUR at shutdown) has the same arrangement.
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Last edited by Smoothie on Tue Aug 05, 2008 3:07 am; edited 1 time in total
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Rasta Monsta  



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PostPosted: Sat Aug 02, 2008 5:08 am    Post subject: Reply with quote

Odd. It sure looks like it would screw in and out of the larger fitting.
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jrcook320  



Joined: 02 Nov 2005
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PostPosted: Sun Aug 03, 2008 12:10 am    Post subject: Reply with quote

That is a standard newer style pressure regulator. The plug does unscrew, but it won't allow you to adjust spring pressure on the regulator plunger. I haven't figured out what hte secondary push valve's function is yet, but the plug is there to allow the push valve to install from the outside of the regulator.




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Smoothie  



Joined: 01 Jan 2003
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PostPosted: Sun Aug 03, 2008 1:47 am    Post subject: Reply with quote

This diagram shows the "push-up valve". When the pressure regulator moves left and closes at shutdown,
the push-up valve also moves left to close the WURs' return path. It prevents pressure loss through the
WUR after shutdown -

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dpw928  



Joined: 02 Nov 2002
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PostPosted: Sun Aug 03, 2008 1:54 am    Post subject: Reply with quote

Now that concludes CIS 201. The hex end is also on my 928 and it is probably there to hold the assembly from turning while the nut is locked.

Dennis
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Rasta Monsta  



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PostPosted: Sun Aug 03, 2008 10:29 am    Post subject: Reply with quote

Ah, very informative.

A guy can dream, can't he?
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jrcook320  



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PostPosted: Mon Aug 04, 2008 11:01 am    Post subject: Reply with quote

dpw928 wrote:
Now that concludes CIS 201. The hex end is also on my 928 and it is probably there to hold the assembly from turning while the nut is locked.

Dennis

The hex is an allen keyway for the plug to be removed from the pressure regulator. There is no locking nut, the 16mm nut is the regulator body itself. The plug is there because it was the only way to manufacture the part. They needed to machine out the inside of the pressure regulator to have an open chamber for fuel to flow. The only way to do that is to lathe it out, and the only way to close it off again is to cap it.

This is where the return from the WUR feeds into. While the pressure regulator is open, the "push up valve", as smoothie posted, opens, allowing fuel to flow into the return line back to the fuel tank. Once the pressure regulator closes, the push up valve closes and stops leak down from the WUR into the tank return circuit.
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