(5)
Gastester does not respond to mixture changes.
Remedy: Check correct fitting of probe pipes, see Fig 2A. Check for water in the
probe pipe. The most common reason for lack of response is no gas flow through the
collector box. (operation of the pulse pump is normally audible as the internal diaphragm
vibrates with pulsations from the exhaust). If response is obtained at higher than idle
speeds only. Pulse Pump may need replacement. (Alternatively, remove the Pulse Pump
and twist the pump cap on the body to re-seat the diaphragm).
(6)
Gastester cannot be set to the Calibration Position in air after warm-up.
Remedy: First check that the unit is correctly assembled according to the
instructions and that the unit is being used the correct way up (the unit will not operate
correctly if the collector box is inclined). Ensure that the unit is connected to a car battery
(nb, a
12v dry cell battery, or a faulty car battery can not provide enough current and are
unsatisfactory). Ensure that the unit is correctly warmed up (allow at least
8
minutes).
Ensure that the unit is being calibrated
tothe calibration mark (near to 2%, NOT at zero).
Ensure that the probe is in air and is not in the exhaust pipe. If these checks do not
resolve the problem, it is possible that the instument has "drifted", generally due to
collector box contamination or damage due to impact. The collector box is more prone
to impact damage when warm and in use. The unit should be returned to
Gunson for
service. Fees for service and re-calibration are shown on the enclosed
Gunson
"Customer Services" leaflet. For further details of services and charges, or any other
enquiries please send a Stamped Addressed Envelope to Service Department,
Gunson
Ltd.
8.
TWINIMULTIPLE CARBURETTORS
Where two separate carburettors are fitted, (not to be confused with a twin choke
carburettor) two extra complications arise. Firstly the air flow through the carburettors
must be accurately balanced before any mixture setting can be undertaken. This can be
done using
Gunson's Carbalancer, or less accurately with atube to listen to the air intake
hiss.
Secondly there will be separate mixture adjustments which must be synchronised.
In the unlikely event that cylinders fed by each carburettor have totally separateexhaust,
Gastester can be used in each exhaust to set the respective carburettor. When the
exhaust
IS
common to all cylinders another method must
be
used. One method is to
count the turns of the mixture adjusting screws from the fully closed
position
(or
jet
Rush
with the bridge for variableventuri types) and then ensure that the screwsare kepttothe
same number of turns throughout adjustment. An alternative (and
better)
memod is to
use
Gunson's Colortune to set the mixture strengths equal at some point, then to ensure
that the screws are turned the same amount during subsequent adjustments.
9.
CARBURETTOR TYPES AND THEIR
ADJUSTMENTS
GENERAL INFORMATION
There are literally hundredsof different types of carburettor in use today, and finding
the appropriate screws that control idle mixture strength and idle speed can pose quite a
To Next Page
Loading...
