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Smart quod bastardus
 
fredmeister's Avatar
 
Join Date: Oct 2002
Location: Baltimore, MD, USA
Posts: 2,235
Garage
Since you said you had removed the plunger and re-polished the plunger shaft with 3M....this likely is the issue. The surface finish and tolerances on that plunger and bore in the CIS meter housing is ridiculously fine and they are likely assembled in matched sets. You may have changed the tolerances or roughened the surface finish so that maintaining consistent idle is difficult. I am not certain but this would be my guess.
It may be worth your while having the unit at least looked at or rebuilt to eliminate this as the cause. They should be able to reset the metering plate for you as well so it is in the proper range at idle too.
Good luck.

Fred

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1979 930 Turbo....3.4L, 7.5to1 comp, SC cams, B&B intercooler, Snow Perf water/meth injection, Rarlyl8 headers, Garret GTX turbo, 36mm ported intakes, Innovate Auxbox/LM-1, custom Manually Adjustable wastegate housing (0.8-1.1bar),--running 0.7bar max
---"When you're racing it's life! Anything else either before or after, is just waiting"
Old 09-08-2008, 10:22 AM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #21 (permalink)
Acceleration Junkie
 
Join Date: Aug 2007
Location: Laguna Beach, CA
Posts: 263
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Quote:
Originally Posted by fredmeister View Post
The surface finish and tolerances on that plunger and bore in the CIS meter housing is ridiculously fine and they are likely assembled in matched sets. You may have changed the tolerances or roughened the surface finish so that maintaining consistent idle is difficult.
I spoke with John at http://specialtauto.com/porsche-parts/index.html explained the symptoms. He could not say the problem was in the head but did say he's surprised the fuel head seems to work well at all. The varnish from dried fuel (10+ years in the making) may be off the plunger but it's still in all the passages, openings and solidified on the internal sealing o-rings.

930Turbo and Nathan: Metering plate pivot is free/smooth and fuel pressures are regulating well. I checked with both the DWUR software and a mechaical CIS fuel pressure gage test set with car running and hot, but not under boost or load.

The bad news, time for a rebuild of the fuel head ($450 + shipping). The good news, how much better the little car is going to run

Thanks to all for your help.
Chris

Old 09-08-2008, 01:50 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #22 (permalink)
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