Operating instructions

Page53
ENGINE CONDITION
DWELLMETERREADINGS
I. Start Mode (cranking) 0 o
.
Warm engine operation at idle
or part-throttle with constant
engine speed. See Note Below.
Constantly varying between
i0_ and 50_ (Higher engine
speeds result in faster
variations.)
3_ Acceleration and deceleration
(changing engine speed)
Constantly varylng between
10_ and 50° (DWELL variations
may not be easily discernible
on the DWELLMETER during
rapid accelerations or decel-
erations but may be seen on
slower changes in engine RPM)
4. Wide open throttle (W. O. T.)
(under engine load--on the road
or with dynamometer).
Approx. 6°
NOTE: The input to the C-4 System which causes the Constantly varying
DWELL reading is an oxygen sensor mounted on the exhaust manifold
working through the ECM. This sensor must typically be above 6000 F
to operate properly. Engine cooling, restart, or excessive idling could
cause the sensor to go below 600°F in which case the DWELLMETER reading
will be some FIXED value between I0° and 50°. This syst@m may require
three to four minutes to reach temperature after a restart or cool-down to
resume the VARYING-DWELL operational mode.
FIGURE 51
ADAYTOR PLUG CONNECTOR
Used to provide Dwell Con-
nection on G.M. C-4 Systems.
Test Number 33--Ground Strap!est(EnginetoBodyJ
The ground strap from the vehicle body to the engine provides the
return circuit from the lights and other accessories to the battery. A
defective ground strap or ground connections could cause an inaccurate
voltage regulator setting, resulting in higher voltages to the electrical
system. The ground strap can be tested as follows: