Automobile Maintenance Guidelines: Diesel Engine

Diesel Engine Faults

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

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

(3) Engine starts but it won’t run smoothly (Engine misses)

(4) Engine overheating.

(5) Knocking sound in the engine.

(6) Loss of engine power.

(7) Abnormal engine oil pressure.

(8) Excessive engine oil consumption.

(9) Excessive engine vibration.

(10) Excessive fuel consumption

(11) Dense smoke at the engine exhaust

(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 loose or corroded.

5. Damaged or disconnected battery cables.

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

7. Starter switch defective or circuit open.

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

Possible Causes :

1. Incorrect starting procedure.

2. Heater plugs defective.

3. Battery discharged.

4. Engine oil too thick.

5. Fuel system defects :

(A) No or insufficient fuel in the tank.
(B) Contaminated or poor quality fuel.

(D) Fuel tank breather blocked.

(E) fuel filters blocked or fuel feed pump inoperative.

(F) Fuel injector pump defective or timing incorrect.

(G) Injectors blocked or fuel spray unsatisfactory.

(H) Fuel inlet pipes to injectors leaking.

6. Insufficient cylinder compression :

(A) Piston rings, cylinders worn out.

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

(C) Improper valves or valve operation :

(a) Valve timing incorrect

(b) Insufficient valve clearance

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

3. Incorrect starting procedure.

4. Heater plugs defective.

5. Battery discharged.

6. Engine oil too thick.

(3) Engine starts but it won’t run smoothly (Engine misses)

Possible Causes :

1. Fuel system defects :

(A) No or insufficient fuel in the tank.

(B) Contaminated or poor quality fuel.

(D) Fuel tank breather blocked.

(E) fuel filters blocked or fuel feed pump defective.

(F) Fuel injector pump defective or timing incorrect.

(G) Injectors blocked or fuel spray unsatisfactory.

(H) Fuel inlet pipes to injectors leaking.

2. Insufficient cylinder compression.:

(A) Piston rings, cylinders worn out.

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

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

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

3. Engine overheated.

4. Restricted exhaust.

(4) Engine overheating.

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 drive belt loose or slipping with oil.

(E) Fan blades warped causing poor air flow.

(F) Fan drive clutch or motor defective.

(G) Radiator cooling and coolant flow restricted due to corrosion.

(H) Thermostat stuck or improperly installed.

(I) 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. Injector pump timing retarded or valve timing incorrect.

6. Engine oil level low or oil filters blocked.

7. Oil pump worn out or oil pressure relief valve leaky.

8. Main or big end bearings worn out.

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

10. Brakes dragging or clutch slipping.

11. Overloading of the engine.

12. Continuous driving in low gears.

13. Hot climate conditions or high altitude operation,

(5) Knocking sound in the engine.

Possible Causes :

1. Combustion knocks :

(A) Improper quality of fuel.

(B) Fuel injector pump defective (Timing advanced)

(D) Injector pressure reduced.

(E) Engine overheating.

(F) Excessive carbon deposits in cylinders.

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 bearing

(F) Flywheel, pressure plate loose

(6) Loss of engine power

Possible Causes :

1. Fuel system defects :

(A) No or insufficient fuel in the tank.

(B) Contaminated or poor quality fuel.

(D) Fuel tank breather blocked.

(E) fuel filters blocked or fuel feed pump defective.

(F) Fuel injector pump defective or timing incorrect.

(G) Injectors blocked or fuel spray unsatisfactory.

(H) Fuel inlet pipes to injectors leaking.

2. Insufficient cylinder compression :

(A) Piston rings, cylinders worn out.

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

(C) Improper valves or valve operation :

(a) Valve timing incorrect.

(b) Insufficient valve clearance.

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

3. Fouled air cleaner

4. Exhaust pipe or silencer blocked.

5. Engine overheated.

6. Excessive carbon deposits in combustion chambers.

7. Defective torque converter (Auto gear box)

8. Use of thick engine oil.

9. Excessive rolling resistance due to smaller diameter tires, dragging brakes or wheel misalignment.

(7) 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 trough 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.

1. High engine oil pressure :

(A) Oil pressure relief valve stuck.
(B) Excessively strong relief valve spring.

(D) Excessively thick engine oil.

(8) Excessive engine oil consumption.

Possible Causes :

1. Engine oil leaking

2. Cylinders or piston sleeves worn out

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

4. Valve guide oil seals worn out

5. Cylinder head gasket damaged or not tight enough.

(9) Excessive engine vibration.

Possible Causes :

1. Engine idle speed too low.

2. Defective vibration damper.

3. Unbalanced or loose fly wheel.

4. Excessive crankshaft end play.

5. Loose or broken engine mounts.

6. Engine missing (Injectors blocked, injector pump defective, valves defective)

7. Power output of each cylinder differs (Injectors blocked, injector pump defective)

(10) Excessive fuel consumption

Possible Causes :

1. Insufficient cylinder compression :

(A) Piston rings, cylinders worn out.

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

(C) Improper valves or valve operation :

(a) Valve timing incorrect

(b) Insufficient valve clearance

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

2. High speed driving or continuous driving in low gears.

3. Clogged air cleaner or exhaust pipe.

4. Engine friction high (Tight bearings and piston rings)

5. Fuel leaks (Through fuel tank, fuel line or connections)

6. Injector pump defective (Timing too advanced, high idle speed, calibration out)

7. Fuel injectors defective (Injector opening pressure low, nozzles clogged, spray unsatisfactory)

8. Clutch slipping or brakes dragging.
9. Excessive rolling resistance due to,
(A) Incorrect wheel alignment.
(B) Under inflated tires.
(C) Under size rims.

(11) Dense smoke at the engine exhaust

Possible Causes :

1. Engine overloaded

2. Air filter blocked

3. Piston rings, cylinders worn out

4. Fuel injector pump defective (worn or calibration, phasing out)

5. Fuel injectors defective (Fouled, needles worn, pressure adjustments out)

6. High pressure fuel line to injectors loose.