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Fault finding - all engines, All engines 1•35, Engine fails to turn when starter operated – FIAT Uno 45 User Manual

Page 49: Engine turns and fails to start, Engine fires but will not run, Engine stalls and will not restart, Engine slow to warm up, Difficult starting when cold, Difficult starting when hot, Engine lacks power

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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

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