Chevrolet 70 1969 Series, Руководство по ремонту

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FUEL TANK AND EXHAUST 8A-3
LATCH PLATE
DIE BLOCK \
TUBE
Figure 5— Flaring Operation— First Flare
9. Blow tubing out with compressed air.
C A U T IO N : When tightening nut on tubing
tighten only to a point sufficient to prevent
leakage.
FUEL GAUGE SYSTEM
T A N K UNIT (Fig. 7)
The fuel tank strainer, fuel pickup pipe, and
tank gauge unit are one assembly. The sock-type
strainer, located on bottom of fuel pickup pipe, is
of plastic wrap construction with a heat sealed end.
The large area fuel strainer is of sufficiently fine
mesh to prevent entrance of contaminants into fuel
system and operates with a self-cleaning action.
Inspect condition of strainer if tankunit is removed
and replace or clean as required.
The tank unit houses a variable resistor (rheo­
stat) which controls current through the dash gauge
according to position of float. The tank unit rheo­
stat may be checked with an ohmmeter. With float
on " E M P T Y " position, ohmmeter connected across
rheostat should indicate .00 to 1.0 ohms resistance.
With float in " F U L L " position, resistance should
measure about 90 ohms for conventional cab models
and 30 ohms for steel tilt models.
D A S H G A U G E
The dash fuel gauge is an electromagnetic in­
strument which visually indicates quantity of fuel
in tank when the ignition switch is turned to the
" O N " or "A C C E S S O R Y " position.
The dash gauge consists of a permanent mag­
netic armature and spindle assembly to which a
pointer is attached. Surrounding the magnetic arm ­
ature are two coils wound perpendicular to each
other. These coils provide the magnetic fueldwhich
deflect the armature and pointer. The intensity and
direction of the resultant magnetic field of the coils
is dependent on current flow controlled by resist­
ance of the tank unit rheostat. When the position of
the slider arm varies due to float action, a change
in rheostat resistance occurs which results in a
1ST OPERATION
UPSET FLARE
PUNCH
SND OPERATION
FINISH FLARE
PUNCH T-3951
Figure 6— Flaring Operation— First and Second Flare
proportional current change in the dash gauge coils.
This allows the armature (and pointer) to align it­
self according to the resultant magnetic field pro­
duced by the coils. The total angular travel of arm ­
ature and pointer from " E M P T Y " to " F U L L " is
90 degrees.
As mentioned previously, the tank unit rheo­
stat resistance is approximately zero ohms when
the fuel tank is empty (float arm is at its lowest
position). As the tank is filled, the tankunit float
arm will rise to increase rheostat resistance which
in turn, will result in the pointer in the dash gauge
to deflect towards the " F U L L ” position.
The dash gauge fixed calibration resistor
shown on Wiring Diagram is connected across the
Figure 7— Gasoline Sending Unit (Typical)
CHEVROLET SERIES 70 -80 H EAVY DUTY TRUCK SH O P M A N U A L