Gunson COLORTUNE G4074 Mode D'emploi page 34

With this type of injection system there is little or no facility for adjustment, (except
perhaps fuel pump pressure, selection of different settings for different octane fuels
etc). When there are no faults present the performance is generally very good under all
operating conditions, but even minor faults may have an exaggerated effect. Colortune
can provide a unique view of the behaviour of the fuel injection system, in the individual
cylinders, which no other equipment can do, saving in many cases time, expense and a
great deal of effort in fault diagnosis.
Fortunately, many systems also have the facility for a limited amount of self diagnosis,
and give fault code information in the form of a blink code (a number indicated by a
flashing led) or more complex forms of data transmission. This may pinpoint the
problem or give some guide to the area that requires investigation. Often the
information requires further analysis as the system does not recognize mechanical
problems only the effect on electronic items and will show for example a lambda
(oxygen) sensor or lambda control system fault in the case of inlet or exhaust manifold
air leaks.
Multiple, twin and twin choke carburettors.
Multiple throttle body injection.
On any system that has multiple throttles, it is important to synchronize the action of
these before setting mixture controls. This ensures that the system is balanced, but
more importantly it aids accurate mixture setting.
The procedure is usually a basic mechanical setup of the following procedure. Release
the linkage; adjust throttle stops to achieve identical air flow, clamp linkage. Check that
throttles begin to open simultaneously when operated by the actual accelerator cable or
rod mechanism, (not some other part of the linkage).
A twin choke carburettor that has both throttle plates in one casting does not usually
progressive opening.
Fixed choke carburetors
If two twin choke carburettors are used the linkage between these must be set to
achieve a synchronized opening.
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