Re: high-pitched...frequency valve

[Oliver Seiler <oseiler@acm.org>]

On Tue, 11 Jan 2000, Randy B wrote:

> Oliver wrote:
> >I've noticed a high-pitched buzzing (the best description I have is that
> >it sounds like an electrical discharge, but continuous) around the area of
> >fuel distributor.
> >Any ideas of what might be causing this?
> 
> Oliver,
> That high pitch noise next to the fuel dist. is probably your
> frequency valve, not sure what it does, Bentley wont tell
> this secret, but when you don't hear it buzzing you have a
> problem.

Looked it up in "How to Tune & Modify Bosch Fuel Injection" (I think
Bentley's has a Bosch fuel injection manual as well which might be
helpful, but I don't have it yet). Not much more information:

The frequency valve is a normally closed, solenoid-operated valve
resembling a D-Jetronic or L-Jetronic injector. Attached to the lower
chambers of the fuel distributor, the frequency valve receives a variable
duty cycle signal from the ECU. When the Lambda sensor detects a lean
running condition the ECU increases the duty cycle to the frequency valve,
thereby increasing the volume of fuel through the injectors. When a rich
exhaust condition is detected, the duty cycle will decrease. This duty
cycle can be measured at a test connector with a dwell meter. If the test
connector cannot be located, then connect the dwell meter to the
appropriate ECU connector...

Not much more information beyond that. The electromechanical nature of it
makes me think it could go bad, but there isn't anything on what would
happen if it does. I also can't tell if it's serviceable. And I still
don't know if the noise is normal. If it's inside the fuel distributor,
the only thing to do would be to get a new one, I would think (assuming
it's not working properly).

-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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