Re: Frequency valve

["jtrealty@xxxx " <jtrealty@xxxx>]

You can hear the freq valve standing next to the car with the engine 
cover closed as long as you don't have a horrible exhaust leak. If it 
is buzzing like an angry cricket the circuit is probably working but 
for a further check use a dwell meter at the diagnostic plug. Look up 
in the workshop manual M:03:01 pin 3 + and pin 2 ground. The value is 
not as important as that the dwell should vary about 10 degrees 
indicating that it is hunting about the "stochiometric mixture" or the 
optimum fuel air ratio. You can also test the micro switch at full 
throttle it should increase the dwell and be steady. Your exact dwell 
reading will vary due to the mixture adjustment setting of your car. 
Refer to D:04:15. You do not need a scope to do ordinary 
toubleshooting but it does impress the customers!
David Teitelbaum
vin 10757


--- In dmcnews@xxxxxxxxxxx, "Walter" <Whalt@xxxx> wrote:
> I agree with John Hervey on this one. You really need an 
oscilloscope to
> see what is going on. The signal going from the ECU to the 
frequency valve
> is a square wave signal oscillating at 70 Hertz. (Switching on and 
off 70
> times a second). The first thing to check for is if the signal is 
present.
> A very cheap and effective way to do that is to listen for the 
frequency
> valve buzzing. It sounds like a noisy fluorescent light fixture 
only
> slightly higher pitched (70 Hertz instead of 50 or 60 Hertz 
depending on
> which part of the planet you are on.) If you are in doubt as to 
whether or
> not you hear it while the engine is running, get a very long handle 
screw
> driver and hold the tip against the valve and put the handle against 
your
> ear. The sound is unmistakable. If you don't hear that sound, then 
you
> know you've got problems. If you do hear the sound and you are 
still
> wondering if the Lambda ECU is properly adjusting the duty cycle of 
the
> signal to the frequency valve, then you need a scope or a dwell 
meter. A
> typical Volt-Ohm-Amp meter won't do this trick.
> 
> I've said too much! :)
> Walt Tampa, FL