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53
ENGINE CONDITION
DWELLMETER READINGS
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:
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