Battery; Ignition; Cranking Voltage; Distributor Resistance - Chevrolet CHEVY VAN G10 SERIES Service Manual

ENGINE 6-10
Fig. 1 9 —Cylinder Balance Test
4. O perate engine on each pair o f cylinders in tu rn and note
engine rpm and m anifold vacuum for each pair. A
variation o f more th an 1 inch o f vacuum or 40 rpm
betw een pairs o f cylinders being tested indicates th a t the
cylinders are o ff balance.

BATTERY

The b attery should be checked w ith special testing eq u ip ­
m ent and to th e equipm ent m anufacturers' specifications. See
6
Section Y for com plete inform ation on b attery tests.
IG N ITIO N
The follow ing additional ignition checks may be m ade w ith
any o f several pieces of equipm ent available for uncovering the
source o f engine difficulties. The specific operating in stru c­
tions o f the equipm ent m anufacturer should be follow ed.
•

Cranking voltage

• Ignition switch
• D istributor resistance
• Secondary resistance
• Ignition o u tp u t and secondary leakage
C RA NKING VO LTAG E (FIG . 20)
1. D isconnect coil prim ary lead at the coil negative term inal
to prevent engine from firing during cranking
2. C onnect voltm eter betw een prim ary term inal o f coil
(resistance wire side) and ground.
3. O perate starting m otor.
a. I f voltage is 9 volts or m ore and cranking speed is
satisfactory, the b attery , starter, cables, starter
sw itch and ignition circuit to coil (by-passing
resistance wire) are in good condition.
b. I f below 9 volts, check circuit until difficulty is
located.
M eter reading
b attery ; defective cables, connections, sw itch or
starter; defective ignition circuit to coil.
below specification-W eak
*
C ra n k in g
resistance in cables or starting m o to r; excessive
m echanical drag in engine.
Uneven cranking speed— Uneven com pression,
defective starter to starter drive.
IG N ITIO N SWITCH
With voltm eter connected as described for the Cranking
Voltage T est, turn ignition switch to ON. V oltage should drop
to 5 to 7 volts as current is now passing through high
resistance wire connected betw een ignition sw itch and (+)
positive term inal o f coil. I f b attery voltage o f 12 volts is
obtained, the starter solenoid is by-passing the high resistance
wire connected betw een ignition sw itch and (+) positive
term inal o f coil, thus th e starter solenoid is n ot functioning
properly to by-pass the ignition resistance wire or the ignition
circuit is incorrectly wired.
N O T E : The voltage drop (12 to 5-7 volts) will only
take place when the points are closed. If the points
are open, the path through the resistance wire will
not be completed.
DISTRIBUTO R RESISTANCE
Use equipm ent as directed by m anufacturer. Excessive
resistance in prim ary circuit m ust be elim inated before co n ­
tinuing w ith test procedure.
Fig. 2 0 —Testing Cranking Voltage
speed below normal—Excessive
C H E V Y V A N SH O P M A N U A L