Table of Contents
Advertisement
Section 1-Trouble Shooting
7
(4)
f.;I\'l;//'iE
COIVTIlVUAl~I
..
Y
l""SSES AT IDLE.
When the engine continually misses on the same cylin-
ders, the fault generally lies in the ignition system.
(a) Isolate the miss by pulling one spark plug cable
at a time from the plugs. Remove the plugs, then clean,
inspect. and adjust them. Replace those that are badly
fouled or burned.
(b) Check the spark plug wires for signs of deteriora-
tion and corrosion and replace them as necessary.
(c) Remove the distributor cap and rotor, then clean,
inspect, and replace them as necessary.
(d) If the above steps do not correct the condition,
check the compression to determine if it is satisfactory,
and check the intake manifold for obstructions.
(5) E/\'GilVE ,U/SSES f:RRATICALLY AT Il)LE.
A miss of this type may be caused by a combination of
things. Check the following in sequence:
(a) Carburetor, including choke operation, idle mix-
ture setting, and fuel level.
(b) The ignition system starting with the spark plugs.
(c) The vacuum lines and fittings for leaks.
(d) Valve operation. Perform a compression test if
the miss persists. Repair the engine as necessary.
(6) E."i(;INE
.U/.~f'IRf;S
OR Hf;SITATES ON AC·
Cf:/~f;R.4.TI01".
This malfunction is usually a combina-
tion of faults in the ignition and fuel system, but also
can be caused by the exhaust system. Perform the fol-
lowing checks in the sequence given:
(a) Check the operation of the exhaust gas control
valve. If it is sticking, free it up or replace it as necessary.
(b) Check the paint on the intake
manifol~
heat riser
passage. If the paint is not burned off, the passage may
be obstructed preventing the carburetor from properly
vaJ:orizing the fuel.
(c) Remove the spark plugs. Inspect, clean, and ad-
just the gap. Replace any plugs that are defective (Jr
lead fouled.
(d) Remove the distributor cap and check the point
gap, distributor shaft clearance, condition of the cam
lobes, and the points. Make the necessary repairs or re-
placements. Check the high tension wiring for signs of
deterioration, and make repairs or replacements as
necessary.
(e) Check the coil and condenser. Replace them if
they are defective.
(f) Check the fuel pump pressure and adjust the car-
buretor fuel level. Check the accelerator pump action
and linkage.
(g)
If
the problem still persists, perform a compres-
sion test and check the valve lash. Check the valve
spring rates and assembled height. Make repairs or re-
placements as necessary.
(7)
f;,\,(;II\'f;
IJOf;S
NOT
Hf;V f;/ .. OP
f'LJ /./.
PO""
f;R. Lack of power is usually caused by poor
'1ression. However, some preliminary checks should
be made. Make sure the throttle opens all the way, that
the choke remains open, and that the governor cut-off
operates properly. After preliminary checks are made,
perform the following operations if the trouble has not
been located.
(a) Check the compression. This wil1 indicate whether
the internal components are operating properly.
(b) If the compression checks within limits, check the
ignition system, including initial timing and distributor
operation.
(c) If the compression and the ignition system are
satisfactory, check the fuel system, including carburetion
and fuel pump pressure.
(d) If the problem still exists, a check of mechanical
components must be made. Check the valve lash, cam
lobe, lift, and valve timing. Make the necessary repairs.
b. Fuel System.
The fuel system consists of the fuel tank, fuel pump,
carburetor, and connecting lines. Dirt and other foreign
material are a major source of fuel system problems.
Keep all components as clean as possible.
(1) EXCESSIJ'E FUEL COI,'SUMPTION. Faulty
carburetion is usually responsible for excessive fuel con-
sumption. However, the following preliminary checks
should be made.
Check for fuel leaks in the system. Check choke opera-
tion and adjustment. and make certain the accelerator
linkage is free. Check to see if the brakes are dragging.
Adjust the carburetor.
(a) Verify the complaint with test equipment installed
in the truck. Show the customer how improper operation
of the truck will affect fuel consumption.
(b) If the test shows fuel consumption to be excessive,
rebuild the carburetor. Since poor carburetion is usually
a combination of internal malfunctions, it is usually not
advisable to try to repair only one system in the car-
buretor. Time will be saved by a complete carburetor
overhaul.
(2) CARIlURETOR Fl .. OODS. Make a visual in-
spection of the carburetor for leaking gaskets or casting
defects. Tap the carburetor bowl. If the flooding stops.
the inlet needle was held open by foreign material. If
the flooding persists, follow the steps below:
(a) Remove the air cleaner and check the choke
operation,
(b) Check the fuel level, the condition of the car-
buretor float, and the fuel inlet needle and seat. Replace
any defective parts.
(c) Check fuel pump pressure. If the pressure is ex-
cessive, the pump was forcing fuel past the fl0at needle.
Rebuild or replace the pump.
c. CoolinA
Systenl.
The cooling system is thermostatically controlled to
Hide quick links:
Advertisement
Table of Contents
