Re: [8v,JH] control-pressure regulator vacuum connections

[Oliver Seiler <oseiler@acm.org>]

On Tue, 29 Feb 2000, Ewan Hopkins wrote:

> [...] 
> Since you don't have the enrichment circuit connected-up, the critical 
> factor, in your case, will be the basic control pressure range of the 
> regulator:  if it is too low for your fuel distributor then you'll get too 
> much fuel flowing and a rich mixture. If you should have the vacuum 
> connector hooked up then you'll be running lean, if anything, rather than 
> rich.

I don't understand this. Based on my reading of the Bentley Bosch FI
manual (page 5-21), it sounds opposite to what you say. For example, at
idle, when the intake manifold pressure is at it's lowest, the vacuum
should be leaning out the mixture (the lower chamber diaphragm will be
pushing the control-pressure valve closed, which will increase the control
pressure, which will lean out the mixture). At full load, when the intake
manifold pressure is higher (i.e., less vacuum), the mixture is enriched
(thus the full-load enrichment).

Based on this reading, since the vacuum connection isn't connected, the
car should be acting as if it's got full-load enrichment all the time,
which it does (poor idle, poor mileage, etc.).

> It's worth checking the electrical connection to the regulator 
> (supplies heater in the regulator, I think) and whether the circuit in the 
> regulator is good, as I've found that if I disconnect mine, it doesn't run 
> very well.  If that's OK, take your car to someone with a fuel presssure 
> gauge and see if the control pressure & main system pressure is within spec.

The electricals seem okay. The regulator has continuity, and the harness
is providing 12 volts.

Getting the fuel pressure checked is probably the first thing I should
have done, but I don't have a gauge yet and I didn't want to pay somebody
to investigate the problem ($$$).

Thanks
Oliver

Oliver Seiler -- Software Developer, Pivotal Software, http://www.pivotal.com
    Scirocco MkII Diary - http://erisian.com/~oseiler/scirocco/index.html


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