Automobile Maintenance Guidelines: Petrol Engine (Fuel Injection)

Petrol Engine (Fuel Injection) Faults

(1) Starter motor won’t crank the engine.
(2) Starter motor cranks the engine but it won’t start.
(3) Rough or unstable idle.
(4) Engine won’t run smoothly (Engine misses).
(5) Engine overheats.
(6) Engine backfires.
(7) Knocking sound in the engine.
(8) Engine lacks power.
(9) Abnormal engine oil pressure.
(10) Excessive engine oil consumption.
(11) Excessive fuel consumption.
(12) Excessive engine vibration.

(1) Starter motor won’t crank the engine.

Possible Causes :

1. Engine jammed.

2. Transmission not in neutral position.

3. Seat belts not fastened.

4. Battery discharged, terminals corroded or loose.

5. Damaged or disconnected battery cables.

6. Starter motor defective or pinion jammed in the fly wheel.

7. Starting switch defective or wire connections improper.

(2) Starter motor cranks the engine but it won’t start.

Possible Causes :

1. Ignition system defects :
(A) Weak battery or insufficient charge.
(B) Defective Ignition coil or distributor.

(D) Spark plugs defective (Burnt, fouled or incorrect plug gaps)

(E) Loose wire connections.

2. Fuel system defects :

(A) No fuel.

(B) Contaminated or improper grade of fuel.

(D) Fuel line or filter blocked.

(E) Fuel system pressure incorrect.
(F) No electricity supply to the fuel pump or injectors.

(G) Cold start valve defective or blocked.

(H) Defective or blocked fuel injectors.

3. Insufficient cylinder compression :

(A) Piston rings, cylinders worn out.

(B) Compression leaks between cylinder head and block due to damaged or improperly tightened gasket.

© Improper valves or valve operation :

(a) Valve timing incorrect.
(b) Insufficient valve clearance.

(d) Valves stuck open due to bent push rod or broken spring.

4. Incorrect starting procedure.

5. Engine oil too thick for weather condition.

6. Air cleaner blocked.

7. Intake air leaking.

8. Defective thermo-time switch, auxiliary air valve, temperature sensor or air flow meter.

9. Loose wire connections.

10. Defective Electronic Control Unit (ECU).

(3) Rough or unstable idle

Possible Causes :

1. Ignition system defects :

(A) Defective Ignition coil or distributor.

(B) Leaky or defective plug wires.

(D) Loose wire connections.

2. Fuel system defects :

(A) Fuel pump blocked, defective or with loose wire contacts.

(B) Fuel line, fuel filter blocked or leaking.

(D) Cold start valve leaking.

(E) Fuel injectors defective or no power supply.

(F) Fuel injector pressure incorrect (Fuel leaking)

(G) Idle speed incorrect (Mixture too rich or lean)

3. Insufficient cylinder compression :

(A) Piston rings, cylinders worn out.

(B) Compression leaks between cylinder head and block due to damaged or improperly tightened gasket.

© Improper valves or valve operation :

(a) Valve timing incorrect.

(b) Insufficient valve clearance.

(d) Valves stuck open due to bent push rod or broken spring.

4. Air cleaner blocked.

5. Intake air leaking.

6. Auxiliary air valve defective (Does not close fully)

7. Temperature sensor defective.

8. Air flow meter defective.

9. Throttle valve switch defective.

10. Throttle butterfly valve does not completely close or open

11. Loose connections in wiring harness or ground.

12. Electronic Control Unit (ECU) defective

(4) Engine won’t run smoothly (Engine misses)

Possible Causes:

1. Ignition system defects :

(A) Defective Ignition coil or distributor.

(B) Leaky or defective plug wires.
(C) Spark plugs burnt, fouled or plug gaps incorrect.

(D) Loose wire connections.

2. Fuel system defects :

(A) Fuel pump blocked, defective or with loose wire contacts.

(B) Fuel line, fuel filter blocked or leaking.

(D) Cold start valve leaking

(E) Fuel injectors defective or no power supply

(F) Fuel injector pressure incorrect (Fuel leaking)

(G) Idle speed incorrect (Mixture too rich or lean)

3. Insufficient cylinder compression :

(A) Piston rings, cylinders worn out.

(B) Compression leaks between cylinder head and block due to damaged or improperly tightened gasket.

© Improper valves or valve operation :

(a) Valve timing incorrect.

(b) Insufficient valve clearance.

(d) Valves stuck open due to bent push rod or broken spring.

(5) Engine overheats.

Possible Causes:

1. Cooling system defects :

(A) Insufficient or no coolant.

(B) Leakage of coolant to outside through radiator, radiator pressure cap, expansion tank, radiator hose, hose connections, water pump seals, drain plug etc.

(D) Fan belt loose or slipping with oil.

(E) Fan blades warped causing poor air flow.

(F) Fan drive clutch defective.

(G) Fan drive motor defective or no electricity supply

(H) Cooling and coolant flow restricted due to corrosion.

(I) Thermostat stuck or improperly installed.

(J) Defective water pump which does not circulate enough water.

2. Temperature gauge or indicator defective.

3. Exhaust system obstructed (high exhaust back pressure.)

4. Improperly operating emission controls.

5. Lean air/fuel mixture

7. Valve timing late (Slack timing chain)

8. Insufficient engine oil level.

9. Cylinder head gasket leaking.

10. Piston rings or bearings too tight causing excessive engine friction.

11. Brakes dragging or clutch slipping.

12. Overloading of the engine

13. Continuous driving in low gears.

14. Hot climate conditions, high altitude operation.

(6) Engine backfires.

Possible Causes:

1. Intake backfiring :

(A) Damaged or leaking spark plug cable insulation

(B) Spark plugs of wrong heat range (Hot plugs)

(D) Defective anti backfire valve

(E) Engine overheated

(F) Leaks in air intake system

(G) Idle mixture too lean (Low fuel)

2. Exhaust backfiring :

(A) Cold start valve leaking (Does not close)

(B) Idle mixture too rich (High fuel)

(D) Exhaust valve clearance insufficient

(E) Exhaust manifold / silencer leaking

(7) Knocking sound in the engine.

Possible Causes:

1. Combustion knocks (Detonation) :

(A) Spark plugs of wrong heat range.

(B) Engine overheated.

(D) Excessive carbon deposits in cylinders.

(E) Cylinder head facing too much.

(F) Waste gate inoperative (Turbo engines)

(G) In low gear when climbing a hill.

2. Mechanical knocks :

(A) Valve clearance excessive

(B) Broken, worn or seized piston rings

(D) Excessive crankshaft end-play.

(E) Damaged main or connecting rod bearings.

(F) Flywheel, pressure plate loose.

(8) Engine lacks power.

Possible Causes:

1. Ignition system defects :

(A) Defective Ignition coil or distributor.

(B) Leaky or defective plug wires.
(C) Spark plugs burnt, fouled or with incorrect plug gaps.

(D) Loose wire connections.

2. Fuel system defects :

(A) Fuel pump blocked, defective or with loose wire contacts.

(B) Fuel line, fuel filter blocked or leaking.

(D) Cold start valve leaking.

(E) Fuel injectors defective or no power supply.

(F) Fuel injector pressure incorrect (Fuel leaking)

(G) Idle speed incorrect (Mixture too rich or lean)

3. Insufficient cylinder compression :

(A) Piston rings, cylinders worn out.

(B) Compression leaks between cylinder head and block due to damaged or improperly tightened gasket.

© Improper valves or valve operation :

(a) Valve timing incorrect.

(b) Insufficient valve clearance.

4. Throttle valve switch defective.

5. Throttle butterfly does not open properly.

6. Air flow meter defective.

7. Clogged air cleaner.

8. Exhaust pipe or silencer blocked.

9. Engine overheated.

10. Excessive carbon deposits in cylinders.

11. Defective torque converter (Auto gear box)

12. Clutch slipping.

13. Use of thick engine oil.

14. Electronic Control Unit (ECU) defective

15. Excessive rolling resistance due to,
(A) Tires with under size rims.

(B) Brakes dragging.

(9) Abnormal engine oil pressure.

Possible Causes:

1. Low engine oil pressure :

(A) Engine oil level insufficient or no oil.

(B) Excessively thin or hot engine oil.

(D) Oil filter contaminated.

(E) Oil pressure indicator defective.

(F) Oil pressure gauge pipe line clogged.

(G) Oil circulation obstructed through pipes, oil gallery, oil pump or oil filter.

(H) Oil leaks through broken or cracked pipe lines, pipe connections, oil gallery or oil seals.

(I) Oil pressure relief valve leaky (Weak springs)

(J) Excessive bearing clearances.

(K) Damaged main or connecting rod bearings.

(L) Wrong grade of oil for weather condition.

(M) Oil pump is worn out.

2. High engine oil pressure :

(A) Oil pressure relief valve stuck.

(B) Excessively tight oil pressure relief valve spring.

(D) Excessively thick oil.

(10) Excessive engine oil consumption.

Possible Causes:

1. Engine oil leaking.

2. Engine oil level too high.

3. Cylinders or piston sleeves worn out.

4. Piston oil rings worn or stuck to the ring grove.

5. Valve guide oil seals worn out.

6. Cylinder head gasket improperly tightened or damaged.

(11) Excessive fuel consumption.

Possible Causes:

1. Fuel leaks.

2. Continuous driving in low gears.

3. High speed driving.

4. Ignition miss (poor spark).

5. Fuel system pressure incorrect.

6. Cold start injector leaking.

7. Temperature sensor defective.

8. Air flow meter defective.

9. CO concentration incorrectly set.

10. Clutch slipping or brakes dragging.

11. Excessive rolling resistance due to,

(A) Wheel misalignment

(B) Under inflated tires

12. Insufficient cylinder compression :

(A) Piston rings, cylinders worn out.

(B) Compression leaks between cylinder head and block due to damaged or improperly tightened gasket.

(a) Valve timing incorrect.

(b) Insufficient valve clearance.

(d) Valves stuck open due to bent push rod or broken spring.

(12) Excessive engine vibration.

Possible Causes:

1. Defective vibration damper.

2. Unbalanced or loose fly wheel.

3. Excessive crankshaft end play.

4. Loose or broken engine mounts.

5. Engine idle speed too low.

6. Engine misses.