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Residual Pressure Mystery :0) HELP !

 
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Sndtech  



Joined: 23 Apr 2013
Posts: 31
Location: Commack, NY

PostPosted: Mon Jun 04, 2018 5:42 pm    Post subject: Residual Pressure Mystery :0) HELP ! Reply with quote

My 80 924 N/A has a residual pressure loss. After just 4 minutes it drops to almost zero.

As part of the restoraton of this car I replaced the below items
and the residucal pressure results are the same

1- New (Rebuilt) Control Pressure Regulator replaceed
2- New Fuel Pump and Check Valve Replaced.
3- New Fuel Accumulator Replaced.
4- New Injectors
5- New Cold Start Valve
6- Fuel Dizzy rebuilt
7- No visual fuel leaks as pressure drops
8- No leaky injctors or cold start valve they have been checked also.

System checked for ai/vacuam leaks and confirmed there are none.
It's a bizarre problem and my mechanic can't figure it out either.

Anyone any ideas as to where I can look for the prioblem ?

Please help ??

Thanks

Manny
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Manny-
1979 924 N/A Dolomite Grey | 1980 924 N/A Minerva Blue
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morghen  



Joined: 21 Jan 2005
Posts: 7857
Location: Romania

PostPosted: Mon Jun 04, 2018 6:16 pm    Post subject: Reply with quote

The rebuild of the WUR (control pressure regulator) was done incorrectly and it is leaking fuel back to the tank.

Loads of people assume that "rebuilding" things makes them work better.
Unless you know what you're doing and using the right parts, it actually makes things worse.
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1556
Location: MI

PostPosted: Tue Jun 05, 2018 3:21 am    Post subject: Reply with quote

Pressure up and then pull the return to tank line banjo off the FD and see if anything is coming out that hole..

If yes then leak = FD or WUR returning fuel..
I suppose the frequency valve could leak by just as well as the wur can, you ever test that?

To test the check valve you could probably pressure up and then pull the fuel line before the main pump and see if you get a continuous leak there after the initial fuel spill..

The accumulator would hold what, a cup or so volume of fuel at pressure before it would leak completely to zero? Some decent little amount of volume you should be able to see go somewhere..
4 minutes should be enough time to pull this and that and see it go somewhere I would think..
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Sndtech  



Joined: 23 Apr 2013
Posts: 31
Location: Commack, NY

PostPosted: Wed Jun 06, 2018 2:16 pm    Post subject: Reply with quote

Thanks Morghen & Fasteddie313 for the advice. I got the Control Pressure Regulator rebuilt by http://fuelinjectioncorp.com/. They seem reputable. I'll try the steps outlined soon.
I just recently pulled another WUR from a perfectly starting 924 NA and will try that also.

Apppreciate the advice as always.. I'll let you know what happens.
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1979 924 N/A Dolomite Grey | 1980 924 N/A Minerva Blue
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