Via Veloce by Wille R.  www.veloce.se  Internet since November 1995 and still here.

Alfa Romeo fault diagnosis. Some common faults and perhaps some reasons. 

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Engine fails to turn when starter operated
Starter motor turns engine slowly but fails to start
Starter motor spins without turning engine
Engine turns normally but fails to start
Engine fires but will not run
Engine cuts out and will not restart
Engine misfires before cutting out - fuel fault
Engine cuts out - other causes
Engine overheats 
Low engine oil pressure  

Whistling or wheezing noises
Tapping or rattling
Knocking or thumping
Engine fires but will not run
Difficult starting when cold
Difficult starting when hot
Engine slow to warm up
Engine idles roughly
Engine lacks power
Engine misfires throughout speed range
Poor engine braking
Pre-ignition (pinking) during acceleration
Engine Backfires
Engine runs on after switching off

Low engine oil pressure Whistling or wheezing noises
Tapping or rattling
Knocking or thumping
Engine fires but will not run
Difficult starting when cold
Difficult starting when hot
Engine slow to warm up
Engine idles roughly
Engine lacks power
Engine misfires throughout speed range
Poor engine braking
Pre-ignition (pinking) during acceleration
Engine Backfires
Engine runs on after switching off

Low oil pressure (verify accuracy of sender before dismantling)
Excessive oil consumption 
Oil stains and spots in the garage 
Oil contaminated with water
Oil contaminated with fuel
Oil smoke
Unusual mechanical noises 

Cooling system overheating
Engine running too cool
Loss of coolant
Heater gives insufficient output
Fuel system - Fuel smell
Smel1 of petrol when engine is idling
Excessive fuel consumption for reasons not covered by leaks or float chamber faults

Difficult starting, uneven running, lack of power, cutting out
Difficult starting when cold
Difficult starting when hot
Engine does not respond properly to throttle
Engine idle sped drops when hot
Engine runs on

Ignition system - Mechanical breaker system
Engine fails to start
Engine starts and runs but misfires
Engine overheats, lacks power
Electronic type - Engine fails to start

Clutch - transmission
Difficulty in engaging gear (grinding)
Clutch spin (failure to disengage) so that gears cannot be meshed
Clutch slip, increase in engine but speed does not increase, road speed
Noise evident when clutch pedal depressed
Noise evident as clutch pedal released
Weak or ineffective synchromesh
Jumps out of gear
Excessive noise in transmission
Difficulty in engaging gears
Noise when cornering

Braking system
Excessive pedal travel
Pedal feels spongy or soggy
Pedal feels springy
Excessive effort required to stop car
Brakes pull to one side
Pedal vibrates when brakes applied
Brakes squeal
Loosing brake fluid

Engine will not start

Top   Engine fails to turn when starter operated

1. Flat battery (recharge, use jump leads, or push start)
2. Battery terminals loose or corroded
3. Battery earth to body defective
4. Engine earth strap loose or broken
5. Starter motor (or solenoid) wiring loose or broken
6. Ignition starter switch faulty
7. Major mechanical failure (seizure)
8. Starter or solenoid internal fault
9. Battery discharged
10. Battery terminals loose or corroded
11. Battery earth to body defective
12. Engine transmission earth strap broken or loose
13. Disconnected or broken wire in starter circuit
14. Disconnected or broken wire in starter circuit
15. Starter pinion jammed in mesh with flywheel gear
16. Starter motor or solenoid defective
17. Major mechanical failure (seizure) or long disuse (piston rings rusted to bores)

Top   Starter motor turns engine slowly but fails to start

1. Partially discharged battery (recharge, use jump leads, or push start)
2. Battery terminals loose or corroded
3. Battery earth to body defective
4. Engine earth strap loose
5. Starter motor (or solenoid) wiring loose
6. Starter motor internal fault
7. Battery discharged
8. Battery terminals loose or corroded
9. Battery or engine earth strap loose
10. Starter motor connections loose
11. Oil in engine / transmission too thick. Release clutch.
12. Starter motor defective

Top  Starter motor spins without turning engine

1. Flat battery
2. Starter motor pinion sticking on sleeve
3. Flywheel gear teeth damaged or worn
4. Starter motor mounting bolts loose
5. Earth strap between engine and chassi weak or loose

Top  Engine turns normally but fails to start

1. Damp or dirty HT leads and distributor cap (crank engine and check for spark)
2. Dirty or incorrectly gapped distributor points (if applicable)
3. No fuel in tank (check for delivery at carburettor)
4. Excessive choke (hot engine) or insufficient choke (cold engine)
5. Fouled or incorrectly gapped spark plugs (remove, clean and regap)
6. Other ignition system fault
7. Other fuel system fault
8. Poor compression
9. Major mechanical failure leg camshaft drive)
10. Fuel tank empty
11. Damp or dirty HT leads, distributor cap or plug bodies
12. Broken, loose or disconnected LT leads
13. Contact breaker points dirty or incorrectly gapped
14. Contact breaker points dirty or incorrectly
15. Other fuel system fault (see Chapter 3)
16. Valve timing incorrect after rebuild)

Top  Engine fires but will not run

1. Insufficient choke (cold engine)
2. Air leaks at carburettor or inlet manifold
3. Fuel starvation
4. ignition fault

Top Engine cuts out and will not restart

1. Engine cuts out suddenly - ignition fault
2. Loose or disconnected LT wires
3. Wet HT leads or distributor cap (after traversing water splash)
4. Coil or condenser failure (check for spark)
5. Other ignition fault

Top Engine misfires before cutting out - fuel fault

1. Fuel tank empty
2. Fuel pump defective or filter blocked (check for delivery)
3. ink filler vent blocked (suction will be evident on releasing cap)
4. Carburettor needle valve sticking
5. Carburettor jets blocked (fuel contaminated)
6. Other fuel system fault

Top Engine cuts out - other causes

1. Serious overheating
2. Major mechanical failure leg camshaft drive)

Top Engine overheats Ignition (no-charge) warning light illuminated

1. Slack or broken drivebelt - fan, ignition warning light not illuminated
2. Coolant loss due to internal or external leakage
3. Thermostat defective
4. Low oil level
5. Brakes binding
6. Radiator clogged externally or internally
7. Electric cooling fan not operating correctly
8. Engine waterways clogged
9. Ignition timing incorrect or automatic advance malfunctioning
10. Mixture too weak

Top Low engine oil pressure Gauge reads low or warning light illuminated with engine slow running

1. Oil level low or incorrect grade
2. Defective gauge or sender unit
3. Wire to sender unit earthed
4. Engine overheating
5. Oil filter clogged or bypass valve defective
6. Oil pressure relief valve defective
7. Oil pick-up strainer clogged
8. Oil pump worn or mountings loose
9. Worn main or big-end bearings

Top Engine noises Pre-ignition (pinking) on acceleration

1. Incorrect grade of fuel
2. Ignition timing incorrect
3. Distributor faulty or worn
4. Worn or maladjusted carburettor
5. Excessive carbon build-up in engine

Top Whistling or wheezing noises

1. Leaking vacuum hose
2. Leaking carburettor or manifold gasket
3. Blowing head gasket
4. Idling mixture too weak in one of the cylinders

Top Tapping or rattling

1. Incorrect valve clearances
2. Worn valve gear
3. Worn timing belt
4. Broken piston ring (ticking noise)

Top Knocking or thumping

1. Unintentional mechanical contact leg fan blades)
2. Worn drivebelt
3. Peripheral component fault (generator, water pump etc)
4. Big-end bearings (regular heavy knocking, perhaps less under load)
5. Worn main bearings (rumbling and knocking, perhaps worsening under load)
6. Piston slap (most noticeable when cold)

Top Engine fires but will not run

1. Insufficient choke (cold engine)
2. Fuel starvation or tank empty
3. Ignition fault (see Chapter 4)
4. Other fuel system fault (see Chapter 3)

Top Difficult starting when cold

1. Insufficient choke
2. Fouled or incorrectly gapped spark plugs
3. Damp or dirty HT leads, distributor cap or spark plug bodies
4. Dirty or maladjusted contact breaker points
5. Ignition fault or timing maladjustment (see Chapter 4)
6. Fuel system or emission control fault (see Chapter 3)
7. Door compression (may be due to incorrect valve clearances, burnt or
8. sticking valves, blown head gasket, worn or damaged pistons, rings or bores)
9. Incorrect valve timing (after rebuild)

Top Difficult starting when hot

1. Incorrect use of manual choke
2. Fuel line vapour lock (especially in hot weather or at high altitudes)
3. Incorrect ignition timing
4. Other fuel system or emission control fault (see Chapter 3)
5. Poor compression (see above)

Top Engine slow to warm up

1. Choke linkage maladjusted
2. Air cleaner temperature control unit defective
3. Thermostat stuck open (see Chapter 2)
4. Other fuel system fault (see Chapter 3)

Top Engine idles roughly

1. Carburettor incorrectly adjusted
2. Other fuel system fault
3. Spark plugs fouled or incorrectly gapped. Ignition timing incorrect
4. Spark plugs fouled or incorrect
5. Widely differing cylinder compressions
6. ignition fault (see Chapter 4)
7. Low battery voltage (charging fault)

Top Engine lacks power

1. Ignition timing incorrect
2. Air cleaner choked
3. Valve clearances incorrect
4. Brake binding
5. Poor compression
6. Other fuel system fault (see Chapter 3)
7. Other ignition system fault (see Chapter 4)
8. Carbon build-up in cylinder head

Top Engine misfires throughout speed range

1. Defective or fouled spark plug
2. Loose, cracked or defective HT lead
3. Maladjusted, sticking or burnt valves
4. Ignition timing incorrect
5. Blown head gasket
6. Fuel! contaminated
7. Other ignition fault (see Chapter -
8. Other fuel system fault (see Chapter 3)

Top Poor engine braking

1. High idle speed
2. Other fuel system fault (see Chapter 3)
3. Low compression

Top Engine backfires

1. Incorrect ignition timing, often retarded
2. Carbs are too lean
3. Fuel cut-off sensor non working (Spica system)
4. Plug wires broken or too old
5. Wrong idle mixture = too lean
6. Cracked exhaust manifold
7. Leaking exhaust system.

 Top Pre-ignition (pinking) during acceleration

1. Incorrect grade of fuel being used
2. Ignition timing overadvanced
3. Engine overheated
4. Excessive carbon build-up
5. Other ignition fault (see Chapter 4)
6. Fuel system fault (see Chapter 3)

Top Engine runs on after switching off

1. Idle speed too high
2. Incorrect type of spark plug
3. Overheating
4. Excessive carbon build-up
5. Other emission control fault

Top Low oil pressure (verify accuracy of sender before dismantling)

How to check the oil pressure and warning light. Easy how to check video.

1. Engine oil level low
2. Engine overheating
3. Incorrect grade of oil in use
4. Oil filter clogged or bypass valve stuck
5. Pressure relief valve stuck or defective
6. Oil pick-up strainer clogged or loose
7. Main or big-end bearings worn
8. Oil pump worn or mountings loose

Top Excessive oil consumption

1. Overfilling
2. Leaking gaskets or drain plug washer
3. Valve stem oil seals worn, damaged or missing after rebuild
4. Valve stems and/or guides worn
5. Piston rings and/or bores worn
6. Piston oil return holes clogged
7. Leaking front crank seal box at crank pulley. Often oil underneath radiator hoses.
8. If the leak is under the exhaust manifold, the top needs to be resurfaced
9. Leaks at the rear of the head, check  the half-moon shaped seals at cam-cover

Top Oil stains and spots in the garage 

1. If there is oil on the underside of the cooling hoses leading to the radiator, too worn front crank seal. To replace, remove the radiator and the crank nut, size 36mm on an Euro engine. Remember the locking plate.
2. Oil on the bonnet's underside, just over the fan. Front crank seal again
3. Oil under the intake manifold,  front crank seal
4. Oil  under the front of the fly wheel housing, check the front crank seal. The rear crank seal will last the engine.
5. Oil spots under the rear of the gearbox, check the rubber boot and gear box ventilation
6. Oil at the front of the differential housing, check the gearbox.
7. Oil under the fins of the differential housing, check the oil seal at the front of the housing-

Top Oil contaminated with water

1. Excessive cold running
2. Leaking head gasket
3. Cracked block or head

Top Oil contaminated with fuel

1. Excessive use of choke
2. Worn piston rings and for bores

Top Oil smoke

1. Blue, thick smoke may come from worn valve guides
2. Worn valves
3. Defective valve seals
4. Worn piston rings. Check compression with oil in cylinder. If compression increases, worn rings.
5. White smoke may be either water from bad head gasket
6. Or may indicate leaking brake booster.

Top Unusual mechanical noises

1. Unintentional mechanical contact leg fan blade)
2. Worn drivebelt
3. Worn valvegear (tapping noises from top of engine) or
4. Peripheral component fault (generator, coolant pump)
5. Bearings (regular heavy knocking, perhaps less when idling
6. Worn main bearings (rumbling and knocking, perhaps worsening under
7. Worn bushes or gudgeon pins worn (light metallic tapping)
8. Piston slap (most noticeable when engine cold)

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