Fault Tracing - Volvo 121 Servicing

FAULT TRACING

The information given below is only intended to serve as a guide in loca-
lizing and temporarily correcting minor faults. After having carried out
any such measures, have them checked and adjusted by an expert me-
chanic.
The engine does start although the starter motor
turns it round at normal speed
1 Check that there is fuel in the tank.
2 If the engine is warm, starting should be done with the accelerator
pedal slowly depressed as far as it will go.
3 In wet weather the sparking plug insulators should be wiped clean and
the distributor cap removed and wiped dry if flash-over is suspected.
4 Check that the fuel line connections on the pump and carburettor are
not leaking and that fuel is supplied to the carburettor.
5 If the engine is turned round for a while without having started, too
rich a fuel mixture can enter the cylinders resulting in the sparking
plugs becoming moist. Blow the cylinders clean by screwing out the
sparking plugs and turning round the engine with the starter motor.
Dry the sparking plugs before fitting them.
If the engine still does not start
1 Remove the ignition cable from each plug in turn. Hold the end of the
cable about
with the ignition switched on. If there is a strong spark the fault is
probably in the sparking plugs, so they should be changed.
2 If only a weak spark is obtained or none at all, check to see whether
the ignition cables are properly inserted -in the distributor and ignition
coil. Remove the cables and clean the contact surfaces.
3 Remove the distributor cover and check and clean all contact surfaces.
Check that the contact breakers close properly when the engine is
turned round. If the contact breaker arm shaft binds, oil it very spa-
ringly.
If the engine misfires, the reason can be:
1 That one of the ignition cables has loosened in the distributor cover or
from the sparking plug.
2 That one or more of the sparking plugs is coated with soot or oiled up,
in which case the plug concerned should be cleaned or changed and
the sparking plug gap adjusted.
3 That the distributor cover and rotor arm can be cracked or damp.
4 That one of the ignition cables is in a poor condition.
5 That the contact breaker gap in the distributor is insufficient or non-
existent.
6 That the contact breakers are badly burnt.
5 4
from the cylinder block while turning round the engine
1
/4"