Fiat 903 CC Automobile User Manual


 
Fault finding - all engines
Note: When investigating starting and uneven running faults, do not be tempted into snap diagnosis. Start from the beginning of the check
procedure and follow it through. It will take less time in the long run. Poor performance from an engine in terms of power and economy is not
normally diagnosed quickly. In any event, the ignition and fuel systems must be checked first before assuming any further investigation needs to
be made.
All engines 1•35
1
Engine fails to turn when starter operated
Battery discharged
Battery terminals loose or corroded
Battery earth to body defective
Engine/transmission earth strap broken or loose
Disconnected or broken wire in starter circuit
Ignition/starter switch defective
Starter motor or solenoid defective (see Chapter 9)
Major mechanical failure (seizure) or long disuse (piston rings rusted
to bores)
Engine turns and fails to start
Battery discharged
Battery terminals loose or corroded
Battery or engine earth strap loose
Starter motor connections loose
Oil in engine/transmission too thick
Starter motor defective
Vapour lock in fuel line (in hot conditions or at high altitude)
Blocked float chamber needle valve
Fuel pump filter blocked
Choked or blocked carburettor jets
Faulty fuel pump
Fuel tank empty
Other fuel system fault (see Chapter 3)
Shorted or disconnected low tension leads
Dirty, incorrectly set, or pitted contact breaker points
Contact breaker point spring earthed or broken
Faulty condenser
Defective ignition switch
Faulty coil
Damp or dirty HT leads, distributor cap or plug bodies
Broken, loose or disconnected LT leads
Ignition leads connected wrong way round
Other ignition fault (see Chapter 4)
Valve timing incorrect (after rebuild)
Engine fires but will not run
Insufficient choke (cold engine)
Fuel starvation or tank empty
Ignition fault (see Chapter 4)
Other fuel system fault (see Chapter 3)
Engine stalls and will not restart
Too much choke allowing too rich a mixture to wet plugs
Float damaged or leaking or needle not seating
Float lever incorrectly adjusted
Ignition failure - sudden
Ignition failure - misfiring precedes total stoppage
Ignition failure - in severe rain or after traversing water splash
No petrol in petrol tank
Petrol tank breather choked
Sudden obstruction in carburettor
Water in fuel system
Engine slow to warm up
Choke linkage maladjusted
Air cleaner temperature control unit defective
Thermostat stuck open (see Chapter 2)
Other fuel system fault (see Chapter 3)
Difficult starting when cold
Insufficient choke
Fouled or incorrectly gapped spark plugs
Damp or dirty HT leads, distributor cap or spark plug bodies
Dirty or maladjusted contact breaker points
Other ignition fault or timing maladjustment (see Chapter 4)
Fuel system or emission control fault (see Chapter 3)
Poor compression (may be due to incorrect valve clearances, burnt
or sticking valves, blown head gasket, worn or damaged pistons,
rings or bores)
Incorrect valve timing (after rebuild)
Difficult starting when hot
Incorrect use of manual choke
Fuel line vapour lock (especially in hot weather or at high altitudes)
Incorrect ignition timing
Other fuel system or emission control fault (see Chapter 3)
Poor compression (see above)
Engine lacks power
Ignition timing incorrect
Contact breaker points incorrectly gapped
Incorrectly set spark plugs
Dirty contact breaker points
Distributor automatic advance and retard mechanisms not
functioning correctly
Other ignition system fault (see Chapter 4)
Air cleaner choked
Carburation too rich or too weak
Fuel filter blocked
Air filter blocked
Faulty fuel pump giving top and fuel starvation
Other fuel system fault (see Chapter 3)
Poor compression
Valve clearances incorrect
Carbon build-up in cylinder head
Sticking or leaking valves
Weak or broken valve springs
Worn valve guides or stems
Worn pistons and piston rings
Burnt out valves
Blown cylinder head gasket (accompanied by increase in noise)
Worn pistons and piston rings
Worn or scored cylinder bore
Brakes binding
Engine misfires throughout speed range
Defective or fouled spark plug
Loose, cracked or defective HT lead
Maladjusted, sticking or burnt valves
Ignition timing incorrect
Blown head gasket
Fuel contaminated
Other ignition fault (see Chapter 4)
Other fuel system fault (see Chapter 3)
Poor engine braking
High idle speed
Other fuel system fault (see Chapter 3)
Low compression