GMC 1976 ZEO 6083 Maintenance Manual page 434

6Y- 54 ENGINE ELECTRICAL
Figure 58-Bench Test of Module Using Tool
J-24642
battery positive . Terminal and black lead to battery
negative terminal . Connect ground terminal of
analyzer to module ground as shown in (figure 58).
Press and hold test button momentary - red then
green, module good ; light stays red module is defec-
tive .
Engine Runs Rough:
1 . Insure that proper fuel is being delivered to
carburetor .
2. Check all vacuum hoses for leakage.
3. Visually inspect and listen for sparks jumping
to ground .
4. Check initial timing, distributor may have
shifted .
5. Check centrifugal advance on engine.
6. Remove all spark plugs and check for usual
defects-proper gap, fouling, cracked insulators inside
and out, etc.
7. Check spark plug wiring.
8. Remove distributor cap and coil assembly by
turning four latches. Inspect cap, coil assembly and
rotor for spark arc-over .
a. Check primary of ignition coil in cap for
continuity (step 1, figure 56). Reading should be zero
or near zero . If not, replace ignition coil .
b. Check secondary of coil (step 2, figure 56).
Use high scale. Reading should not be infinite .
c . If reading is infinite, check cap and rotor
button for arced or burned condition. If necessary,
replace cap. If cap and carbon button do not appear
defective, replace ignition coil .
9. If trouble has not been located, proceed with
Test No . 2 using J-24642, step 8 (a thru c) .
DISTRIBUTOR COMPONENT
REPLACEMENT
Following is the complete distributor disassem-
bly of which part or all can be used as required .
When necessary to remove the distributor from the
engine, the procedure is the same as for the standard
distributor.
DISTRIBUTOR REMOVAL
1 . Disconnect wiring harness connectors at side
of distributor cap.
2. Remove distributor cap from housing by
releasing four cap retaining latches. Position cap out
of way.
NOTE : Be careful not to damage latches. Posi-
tion screwdriver at top of latch and turn .
3. Disconnect vacuum advance hose from
vacuum advance mechanism.
4. Scribe a mark on engine in line with rotor.
Note approximate position of distributor housing in
relation to engine .
NOTE : To insure correct timing of the distribu-
tor, the distributor must be installed with the
rotor correctly positioned.
5 . Remove distributor clamp screw and hold-
down clamp.
6. Lift distributor from engine . Again note posi-
tion of distributor housing in relation to engine .