GMC 1976 ZEO 6083 Maintenance Manual page 617

12- 12 CHASSIS ELECTRICAL
* Ignition switch must be "OFF" before removing tank sending unit, otherwise full battery voltage may des-
troy unit or ignite fuel vapors . For maximum safety, remove cable from negative battery terminal .
A_i790
Figure 19-Fuel Gauge System Diagnosis
POSSIBLE COMPLAINT
GAUGE AT DASH
" tiGt
at`
tee"
WIRING CONNECTOR
,y1
0~" V
.~
/ 4~0
/ 'GNITION SWITCH
Ot
~e
e ~
a e
t
OJ
TANK
-
UNI
_
pie'ti
'1,
RESISTOR
+
T
p
t
' .
eO
yeti
Dot
V,
et` et`
r
O
FULL
R
SLIDER BATTERY
~~rG
t e1\pe5~
~ti
~~ ~3~~ .~~ .
~' a
ti~
m G p4 a ." ~ ."' {
"~
t
,
~p0
EMPTY,-,
i~_
aGJ ~GJ ~V
1F'
~'J a~J a5 ,a5 5 ~,~}
G
PROBABLE CAUSE
e
4e tte
,fi e ~e ,¢e ¢ e ,¢e
SUGGESTED REMEDIES
1 . Loose connection anywhere in circuit x
Inspect
and, if necessary, clean and
tighten all connections in circuit
2 . Poor dash fuel gauge calibration x Install new dash fuel gauge
3 . Poor tank unit calibration x
stall new tank unit*
4 . Circuit grounded in resistor of tank unit x x
nstall new tank unit
5 . Circuit grounded between tank unit x
sulate grounded circuit
resistor and dash gauge
r
6 . Circuit within dash gauge grounded . x
.Install new dash fuel gauge
7 . Circuit grounded between battery and
x Insulate grounded circuit
dash gauge .
8 . Open circuit between ignition switch
x Clean and tighten appropriate
and dash gauge
terminals or repair broken wire
9 . Open circuit between ground terminal
x Clean and tighten mounting bracket
on gauge and ground
where contact is made between
dash gauge and ground
10 . Open circuit between sending unit
x Clean and tighten appropriate
terminal on dash gauge and
terminals or repair broken wire
resistor terminal on tank unit
11 . Open circuit in resistor of tank unit at x Install new tank unit*
1/4 full position
12 . Open circuit between tank unit slider x Install new tank unit
resistor and ground
13 . Needle rubbing on face of gauge
x x x x x
Position needle to prevent contact
- with face or install new gauge
14 . Fuel tank float hang-up x
x x x x x
Free binding float or install new
tank unit
15 . Top of fuel tank deformed
x
Straighten tank top or replace tank
16 . Bottom of fuel tank deformed
x Straighten bottom of tank or replace
tank
17 . Tank unit mounting flange bent
x
x x Straighten mounting flange or re-
place tank unit*