Control Pressure Problem

[ydrogs at gmail.com (Gordy Stedman)]

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