Duty cycle for 84 240DL

Checked the duty cycle on my 84 wagon and reset it to 50%
assuming that this is the optimum value, but it has seemed
to have leaned the engine out some. Does anyone have the
recommended value? I have a Haynes manual that does not
mention a value, I have heard the Bentley manual may have
the recommended setting. B23F engine.
JD

 

I've heard conflicting numbers, what I ended up doing was measuring a
well-running Kjet 240 and setting mine to match it, the adjustment is
very sensitive though, best not messed with unless someone has already
messed it up.

 

I have the Volvo shop manuals for my '84...all 17 volumes of them.
What engine do you have? More specifically, do you have a turbo with
the fuel distributor in the right front corner of the engine bay or do
you have the K-jet? You have to disconnect the oxygen sensor to set it
properly. If the dwell reading is absoutely constant, there is a problem
someplace. If you're still interested, I'll look it up but, the
duty-cycle is supposed to fluctuate between something like 43 to 46.
Those are not the actual figures, just off the top of my head. Once it's
at the proper value, then reconnect the o2 sensor.

 

He said right in the original post, B23F engine, that's a non-turbo 2.3
liter.

 

OK. Then does it have a CI system or LH or whatever else Volvo used in
'84?

Bob

 

It has CIS (K-jet), otherwise there'd be no duty cycle to adjust.

 

What I mean by the duty cycle is the amount of times the O2
sensor goes from lean to rich. I have heard that this can be
set with a led off the lead next to the coil but I must be
doing something wrong. Manuals refer to the Volvo Monotester
but I can't get a decent reading off my dwell meter. I have
looked and have yet to find the definitive method of setting
the O2 sensor frequency, duty cycle, CO level or whatever
you would like to call this adjustment. It appears to be a
necessity for achieving the proper fuel-air mixture.
jd

 

A dwell meter set for four cyl between the pink test lead and ground,
engine running, will show 53.7*, O2 sensor disconnected. The setting
value should be between 45*-55* engine idling at ~850rpm, warm, throttle
switch contacts closed, dipstick fully seated, no vacuum hose leaks,
ignition showing between 5*and 10* BTDC.

This establishes the mixture setting at idle. All other mixture
corrections during running are regulated by the control pressure and
manifold vaccum changing the height of the air flow sensor plate above
the venturi. There is virtually no correction for restricted injectors,
leaking injector seals, or faulty pressure regulation. The theory being
that if the idle setting is close enough at idle then the converter and
the above mentioned controls will be more than adequate to maintain an
emission level within the regulation in effect at the time.

Bob

 

In 1984 Volvo referred to injector open time as dwell, prior to the
current jargon of referring to pulse width modulation. Using the same
test lead as the OP mentioned you could adjust the mixture, hence the
injector dwell, just by reading the voltage sweep at the test point.
Same procedure just different numbers.

Bob

 

Bob...
I just love you guys that want to further complicate what the Volvo shop
manual states VERY simply.
Simply put...don't overcomplicate the obvious.