Chevrolet 30 Series 1967 Service Manual page 289

Fig. 16—Testing Cranking V oltage
starter switch and ignition circuit to coil (by­
passing resistance wire) are in good condition,
b. If below 9 volts, check circuit until difficulty is
located.
Meter reading below specification—Weak bat­
tery; defective cables, connections, switch or
starter; defective ignition circuit to coil.
Cranking speed below normal—Excessive re­
sistance in cables or starting motor; excessive
mechanical drag in engine.
Uneven cranking speed—Uneven compression,
defective starter or starter drive.
I g n i t i o n S w i t c h
With voltmeter connected as described for the Cranking
Voltage Test, turn ignition switch to ON. Voltage should
drop to 5 to 7 volts as current is now passing through
high resistance wire connected between ignition switch
and (+) positive terminal of coil.
12 volts is obtained, the starter solenoid is by-passing
the high resistance wire connected between ignition
switch and (+) positive terminal of coil, thus the starter
solenoid is not functioning properly to bypass the ignition
resistance wire or the ignition circuit is incorrectly
wired.
D i s t r i b u t o r R e s i s t a n c e
Use equipment as directed by manufacturer. Excessive
resistance in primary circuit must be eliminated before
continuing with test procedure.
S e c o n d a r y R e s i s t a n c e
Use equipment as directed by manufacturer.
• Uniform "normal readings" as specified by manu­
I g n i t i o n O u t p u t a n d S e c o n d a r y L e a k a g e
Carburetor
idle vent, float level, pump rod and secondary valve.
formance, the fuel pump may be at fault.
pump pressure or volume will cause a high speed " m is s "
because of lack of fuel delivered to the carburetor,
while too high a pressure will cause carburetor flooding.
Check fuel pump as outlined in Section
Cooling System
testing equipment available commercially for this pur­
pose.
internal or external leaks within the cooling system.
Cylinder Head Torque and Valve Adjustment
unless a gasket has been replaced, or a leak is suspected.
If battery voltage of
Valve lash must always be adjusted after the head has
been torqued.
portant that the engine be thoroughly warmed up to
normalize the expansion of all parts.
portant because during the warm-up period, the valve
clearance will change considerably.
facturer indicate all secondary circuit components
are in good condition.
• If all readings are "below norm al," check for cor­
roded coil tower terminal, poorly connected or
broken coil wire, center cap electrode or rotor tip
burned, or an open secondary in coil.
• If readings are "higher than norm al" at two or more
plugs adjacent in firing order, cross firing is occur­
ring in distributor cap or between spark plug cables
concerned.
• If meter reads off scale to left, the coil polarity is
reversed. Check for reversed coil primary wires,
wrong coil or reversed vehicle battery connections.
Use equipment as directed by manufacturer.
• GOOD readings indicate both ignition output and
secondary insulation are good.
• If all readings are BAD or if ignition test calibrator
cannot be adjusted to Set Line, check for high re sis­
tance in primary circuit, defective distributor points,
coil or condenser.
• If readings are BAD when certain plug wires are
lifted off, check for cracks or carbon tracks in dis­
tributor cap or defective insulation on those plug
wires being lifted off.
Refer to Section M to perform adjustments such as
6
Fuel Pump
If the owner has complained of poor high speed per­
The following test may be performed with pressure
This test provides an excellent means of detecting
1. Remove radiator cap.
2. Apply a test pressure of 3 pounds higher than the
radiator cap (fig. 17). 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.
Retorquing the cylinder head bolts is not necessary
Before adjusting the valve lash, it is extremely im­
1. After the engine has been normalized, remove rocker
arm covers and gaskets.
CAUTION: Do not pry rocker arm cover loose.
Gaskets adhearing to cylinder head and rocker
arm cover may be sheared by bumping end of
rocker arm cover rearward with palm of hand or
a rubber mallet.
ENGINE 6-9
Too low a
M.
6
This is very im­
CHEVROLET TRUCK SERVICE M ANUAL