Control Pressure Problem

[roccit_53 at scirocco.cs.uoguelph.ca (C Boyko)]

Good for you!! Posting the cure, what an excellent thing that is!. And a 79
Rabbit in a yard? Not around here unless it was MY yard, they crush them
unless they're really new. And my fuel distributor problem didn't show with
the fuel pressure tests, that's interesting. Mine behaved well at idle, but
did not do well under load. Volume tests identified mine (again, they were
fine with the plate just slightly raised).
I'm starting to think this is like "lupus" for our cars, try everything
else, then come around to the diagnosis of bad distributor. Fuel delivery
is there, it's just not right, some of the time. Glad you found it at any
rate, it's SO nice when they finally do what they're capable of.

Cathy

On 1:18 am 06/12/07 "Gordy Stedman" <ydrogs@xxxxxxxxx> wrote:
> Just to add some closure Sean got a used fuel distributor from the
> yard off a 79 rabbit, swapped it out and it starts right up.  Have
> not hooked up the fuel pressure tester to see what the numbers are
> but it responds like a real VW should.  Just need to turn down the
> idle a little and replace noisy wheel bearins.  We think the PO who
> fucked everything up on the car had the wrong fuel distributor on the
> air box. Need to get a photo of the bolt used to hold on the rear
> control arm clamp, yikes.
>
> On 6/3/07, Gordy Stedman <ydrogs@xxxxxxxxx> wrote:
> >
> >  On 6/3/07, Cris Carpenter <housecall55@xxxxxxxxx> wrote:
> > >
> > >  CIS-E and plain CIS are not the same, and an 81 will have only
> > >  one fuel pump. If the control pressures are indeed as high as
> > >  the system pressure, something is blocking the return through
> > >  the control loop. Are you simply substituting one bad WUR for
> > >  another? If the control pressures are that high, it should have
> > >  a real hard time running at all, but especially cold. If you are
> > >  sure you are using a known good WUR, the problem must be the
> fuel distributor. The control loop uses some fuel pressure to hold the
> > >  fuel distributor plunger down. The air flap of the fuel
> > >  distributor has to overcome the control pressure to raise the
> > >  piston and let more fuel to the injectors. The control pressure
> > >  is lower when cold by virtue of the WUR bleeding it off through
> > >  the return circuit back to the tank, allowing the piston to ride
> > >  higher and let more fuel to the injectors until the engine
> starts to warm up. But both the feed and return side of the warm-up
> > >  loop on an 81 goes through the fuel
> > >  distributor. If you are acccurately testing the control
> > >  pressures (I've seen people set it up wrong), have tried a known
> > >  good WUR, and you still have control pressures that high, the
> > > problem must be the fuel distributor.
> > >  Cris
> >
> >  That was what we were coming up as a conclusion also. Thanks for
> >  the detailed explanation.  It does run badly when cold and would
> >  not start at all until we fixed the cold start injector circuit.
> >  We will be swapping out the fuel distributor, maybe complete air
> >  box assembely sometime this week. Hope it works.
> >  --
> >  Gordy
> >  MK1 x 5
> >
>
>
>
> --
> Gordy
> MK1 x 5
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