A9 Light Vehicle Diesel Engines

  • General Diagnosis
  • Cylinder Head and Valve Train Diagnosis and Repair
  • Engine Block Diagnosis and Repair
  • Lubrication and Cooling Systems Diagnosis and Repair
  • Air Induction and Exhaust Systems Diagnosis and Repair
  • Fuel System Diagnosis and Repair

Light Vehicle Diesel Engines

A. General Diagnosis (9 questions)

1. Verify the complaint, and road/dyno test vehicle; review driver/customer concerns and vehicle service history (if available); determine further diagnosis.

2. Record vehicle identification number (VIN). Identify engine model, calibration and serial numbers to research applicable vehicle and service information, service precautions, and technical service bulletins; determine needed actions.

3. Perform scan tool check and visual inspection for physical damage and missing, modified, or tampered components; determine needed repairs.

4. Check, and record electronic diagnostic codes, freeze frame and/or operational data; monitor scan tool data; clear codes; determine further diagnosis.

5. Inspect engine assembly and compartment for fuel, oil, coolant, exhaust, or other leaks; determine needed repairs.

6. Inspect engine compartment wiring harness, connectors, seals, and locks; check for proper routing and condition; determine needed repairs.

7. Listen for and isolate engine noises; determine needed repairs.

8. Isolate and diagnose engine related vibration problems; determine needed actions.

9. Check engine exhaust for odor and smoke color; determine further diagnosis.

10. Check fuel for contamination, quantity, quality, and consumption; determine needed actions.

11. Perform crankcase pressure test; determine further diagnosis.

12. Diagnose surging, rough operation, misfiring, low power, slow deceleration, slow acceleration and shutdown problems; determine needed actions.

13. Check cooling system for freeze point, level, contamination, temperature, pressure, circulation, and fan operation; determine needed repairs.

14. Check lubrication system for contamination, oil level, temperature, pressure, filtration, and oil consumption; determine needed repairs.

15. Diagnose no cranking, cranks but fails to start, hard starting, and starts but does not continue to run problems; determine needed actions.

16. Diagnose engine problems caused by battery condition, connections, or excessive key-off battery drain; determine needed repairs.

17. Diagnose engine problems resulting from an undercharge, overcharge, or a no-charge condition; determine needed action.

B. Cylinder Head and Valve Train Diagnosis and Repair (5 questions)

1. Remove, inspect, disassemble, and clean cylinder head assembly(s).

2. Inspect threaded holes, studs, and bolts for serviceability; service/replace as needed. 

3. Measure cylinder head thickness, and check mating surfaces for warpage and surface finish; inspect for cracks/damage; check condition of passages; inspect core and gallery plugs; determine serviceability and needed repairs.

4. Inspect valves, guides, seats, springs, retainers, rotators, locks and seals; determine serviceability and needed repairs.

5. Inspect and/or replace injector sleeves, glow plug sleeves, and seals; pressure test to verify repair (if applicable); measure injector tip, nozzle, or prechamber protrusion where specified by manufacturer.

6. Inspect, and/or replace valve bridges (crossheads) and guides; adjust bridges (crossheads) if applicable.

7. Reassemble, check, and install cylinder head assembly and gasket as specified by the manufacturer.

8. Inspect pushrods, rocker arms, rocker arm shafts, electronic wiring harness, and brackets; repair/replace as needed.

9. Inspect, install, and adjust cam followers and retainers; adjust valve clearance.

10. Inspect, measure, and replace/reinstall overhead camshaft and bearings; measure and adjust endplay.

C. Engine Block Diagnosis and Repair (5 questions)

1. Remove, inspect, service, and install pans, covers, ventilation systems, gaskets, seals, and wear rings.

2. Disassemble, clean and inspect engine block for cracks; check mating surfaces and related components for damage or warpage and surface finish; check deck height; check condition of passages, core, and gallery plugs; inspect threaded holes, studs, dowel pins and bolts for serviceability; service/replace as needed.

3. Inspect and measure cylinder walls for wear and damage; determine needed service.

4. Inspect in-block camshaft bearings for wear and damage; replace as needed.

5. Inspect, measure, and replace/reinstall in-block camshaft; check and correct end play; inspect, replace/reinstall, and adjust cam followers (if applicable).

6. Clean and inspect crankshaft and journals for surface cracks and damage; check condition of oil passages; check passage plugs; measure journal diameters; check mounting surfaces; determine needed service.

7. Determine the proper select-fit components such as pistons, connecting rod and main bearings.

8. Inspect and replace main bearings; check cap fit and bearing clearances; check and correct crankshaft end play.

9. Inspect and time the drive gear train components (includes gear, chain, and belt systems).

10. Inspect, measure, or replace pistons, pins, and retainers.

11. Measure piston-to-cylinder wall clearance.

12. Identify piston, connecting rod bearing, and main bearing wear patterns that indicate connecting rod and crankshaft alignment or bearing bore problems; check bearing bore and bushing condition; determine needed repairs.

13. Check ring-to-groove fit and end gaps; install rings on pistons. Assemble pistons and connecting rods and install in block; check piston height/protrusion; check liner height/protrusion (if applicable); replace rod bearings and check clearances; check condition, position, and clearance of piston cooling jets (nozzles).

14. Inspect crankshaft vibration damper.

15. Inspect flywheel/flexplate and/or dual-mass flywheel (including ring gear) and mounting surfaces for cracks, wear, and runout; determine needed repairs.

D. Lubrication and Cooling Systems Diagnosis and Repair (6 questions)

1. Verify engine oil pressure and check operation of pressure sensor/switch and pressure gauge; verify engine oil temperature and check operation of temperature sensor.

2. Inspect, measure, repair/replace oil pump, housing, drives, pipes, and screens; check drive gear clearance.

3. Inspect, repair/replace oil pressure regulator valve(s), and by-pass valve(s).

4. Inspect, clean, test, reinstall/replace oil cooler, by-pass valve, lines and hoses.

5. Inspect turbocharger lubrication and cooling systems; repair/replace as needed.

6. Change engine oil and filters; add proper type, viscosity, and rating of oil.

7. Inspect and reinstall/replace pulleys, tensioners and drive belts; adjust drive belts and check alignment.

8. Verify coolant temperature; check operation of temperature and level sensors, switch, and temperature gauge.

9. Inspect and replace thermostat(s), by-passes, housing(s), and seals.

10. Flush and refill cooling system; add proper coolant type; bleed air from system.

11. Inspect and replace water pump, housing, hoses, and idler pulley or drive gear.

12. Inspect radiator, pressure cap, and tank(s); pressure test cooling system and radiator cap; determine needed repairs.

13. Inspect, repair/replace fan, fan hub, clutch, controls, and shroud.

E. Air Induction and Exhaust Systems Diagnosis and Repair (12 questions)

1. Perform air intake system restriction and leakage tests; determine needed actions.

2. Perform intake manifold pressure tests; determine needed actions.

3. Inspect, service/replace air induction piping, air cleaner, and element.

4. Inspect test, and replace turbocharger(s) (including variable ratio/geometry VGT), pneumatic, hydraulic, and electronic controls and actuators; inspect, test, and replace wastegate and wastegate controls.

5. Inspect and replace intake manifold, gaskets, temperature and pressure sensors, and connections.

6. Inspect, test, clean, replace charge air cooler and piping system.

7. Perform exhaust back pressure and temperature tests; determine needed actions.

8. Inspect, repair/replace exhaust manifold, gaskets, piping, mufflers, exhaust after treatment devices, and mounting hardware.

9. Inspect, test, and repair/replace preheater/inlet air heater, and/or glow plug system and controls.

10. Inspect, test, and replace exhaust after treatment system components and controls; check regeneration system.

11. Inspect, test, service, and replace EGR system components; including EGR valve(s), cooler(s), piping, electronic sensors, controls, and wiring.

12. Inspect, test, and replace EGR air-flow control (throttle) valve and controls.

13. Inspect, test, and replace crankcase ventilation system components.

F. Fuel System Diagnosis and Repair (13 questions)

1. Inspect, clean, test, and repair/replace fuel system tanks, vents, caps, mounts, valves, single/dual supply and return lines, and fittings.

2. Inspect, clean, test, repair / replace fuel transfer and / or supply pump, strainers, fuel/water separators/indicators, filters, heaters, coolers, ECM cooling plates (if applicable), and mounting hardware.

3. Check fuel system for air; determine needed repairs; prime and bleed fuel system; check, repair/replace primer pump.

4. Inspect, test, repair/replace low pressure regulator supply and return systems.

5. Inspect, reinstall/replace high-pressure injection lines, fittings, seals, and mounting hardware.

6. Inspect, adjust, repair/replace electronic throttle and PTO control devices, circuits, and sensors.

7. Perform on-engine inspections, tests, and replace high pressure common rail fuel system components and electronic controls.

8. Perform on-engine inspections, tests, and replace hydraulic electronic unit injectors (HEUI) components and electronic controls (rail pressure control).

9. Perform on-engine inspections, tests, and replace pump-line-nozzle fuel system (PLN-E) components and electronic controls.

10. Perform on-engine inspections, tests and replace electronic unit injectors (EUI) components and electronic controls.

11. Inspect and replace electrical connector terminals, pins, harnesses, seals, and locks.

12. Connect diagnostic tool to vehicle/engine; access, verify and update software calibration settings; perform ECM re-learn procedures as needed.

13. Use a diagnostic tool (hand-held or PC based) to inspect and test electronic engine control system, sensors, actuators, electronic control modules (ECMs/PCMs), and circuits; determine further diagnosis.

14. Measure and interpret voltage, voltage drop, amperage, and resistance readings using a digital multimeter (DMM) or appropriate test equipment.

15. Diagnose engine problems resulting from failures of inter-related systems (for example: cruise control, security alarms/theft deterrent, transmission controls, electronic stability control, non-OEM installed accessories).