Fuel System Testing - UNI-T UT105 Operating Manual

Measurement Operation(23)
(4) The normal starting rotation speed of an engine is
about 50 RPM to 275 RPM. Refer the detailed position
to the servicing handbooks of various kinds of automotive
manuals because this value relates to the current
temperature, engine size, battery size, etc.
Warning:
l The displayed value of the meter becomes the
actual tach reading only after it is multiplied by 10.

6.Fuel System Testing

It is necessary to add more accurate engine fuel control
to a low injection automobile. Since 1980, the automotive
manufacturing industry has used electronically-controlled
carburetor and fuel injection so as to achieve lower fuel
injection.
(1) GM (General Motor): Testing the dwell of the C-3
mixed-control solenoid: Place the solenoid in a cylinder,
monitoring the ratio between the air and the fuel, which
should generally be 14.7 to 1 between the air and the
fuel so as to reduce the injection of surplus fuel. The
testing is used to see if the solenoid is installed right
in the position and the dwell of the meter can also
indirectly used for the testing.
A. Start the engine of the automobile to achieve a
rotation speed of 3000 RPM.
So far as a GM automobile is concerned, set the
rotary switch to the DWELL and select 6CYL.
B. When the automobile is operating in a short fuel
state or in a long fuel state, the dwell of the meter
should be displayed between 10
Model UT105: OPERATING MANUAL
o
and 50
39
o
.