Secondary Resistance; Ignition Output And Secondary Leakage; Carburetor; Fuel Pump - Chevrolet CHEVY VAN G10 SERIES Service Manual

SECONDARY RESISTANCE

Use eq uipm ent as directed by m anufacturer.
• U niform " norm al readings" as specified by m an u ­
facturer indicate all secondary circuit com ponents
are in good condition.
• If all readings are "below norm al," check for
corroded coil low er term inal, poorly connected or
broken coil wire, center cap electrode or ro to r tip
burned, or an open secondary in coil.
• If readings are "higher th an norm al" at tw o or more
plugs adjacent in firing o rd er, cross firing is occuring
in d istributor cap or betw een spark plug cables
concerned.
• If m eter reads o ff scale to left, the coil polarity is
reversed. Check fo r reversed coil prim ary wires,
wrong coil or reversed vehicle b attery connections.
IG N ITIO N OUTPUT AND SECONDARY LEAKAGE
Use eq uipm ent as directed by m anufacturer.
• GOOD reading indicate b o th ignition o u tp u t and
secondary insulation are good.
• If all readings are BAD or if ignition test calibrator
cannot be adjusted to Set Line, check for high
resistance in prim ary circuit, defective d istributor
points, coil or condenser.
• If reading are BAD when certain plug wires are
lifted off, check for cracks or carbon tracks in
distributor cap or defective insulation on those plug
wires being lifted off.

CARBURETOR

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Refer to Section M to perform adjustm ents such as idle
vent, fast idle, pum p rod and vacuum break.
Fig. 2 1 —Cooling System Pressure Test

FUEL PUMP

If the ow ner has com plained o f poor high speed per­
form ance, th e fuel pum p may be at fault. Too low a pum p
pressure o f volume will cause a high speed " miss" because of
lack o f fuel delivered to th e carburetor, while to o high a
pressure will cause carburetor flooding. Check fuel pum p as
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outlined in Section M.
COOLING SYSTEM
The follow ing test may be perform ed w ith pressure testing
equipm ent available com m ercially for this purpose. This test
provides an excellent means o f detecting internal or external
leaks w ithin the cooling system .
1. Remove radiator cap.
2. Apply a test pressure o f 3 pounds higher than the
radiator cap (Fig. 24), i.e. 18 pounds for a 15 pound cap.
3. If the pressure will not hold, there is either an internal or
external leak in the system .
C Y LIN D E R HEAD TORQUE AND
V A LV E ADJUSTMENT
Retorquing the cylinder head bolts is not necessary unless a
gasket has been replaced, or a leak is suspected. Valve lash
m ust always be adjusted after the head has been torqued.
H Y D R A U LIC V A L V E ADJUSTMENT
1. Remove rocker arm cover(s) and gasket(s).
C A U T IO N : Do not pry rocker arm cover loose.
Gaskets adhering to cylinder head and rocker arm
cover may be sheared by bumping end of rocker
arm cover rearward w ith palm o f hand or a rubber
mallet.
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2. Adjust valves on L engines as follows:
a. Mark distributor housing, with chalk, at num ber
one and num ber six positions (plug wire) then
disconnect plug wires at spark plugs and coil and
remove distribu tor cap and plug wire assembly (if
not previously done).
b. Crank engine until distributor rotor points to
num ber one cylinder position and breaker points
are open. The following valves can be adjusted with
engine in num ber one firing position:
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L Engine — N um ber one cylinder-Exhaust and
Intake
N um ber tw o cylinder-Intake
N um ber three cylinder-Exhaust
N um ber four cylinder-Intake
N um ber five cylinder-Exhaust
c. Back o u t adjusting n u t until lash is felt at the push
rod then tu rn in adjusting n u t until all lash is
removed. This can be determ ined by checking push
rod end play while turning adjusting nut (Fig. 22).
When play has been rem oved, tu rn adjusting nut in
one full additional turn (to center lifter plunger).
d. C rank engine until d istributor ro tor points to
num ber six position and breaker points are open.
ENG INE 6-11
C H E V Y V A N SH O P M A N U A L