Isuzu Hitachi 4HK1 6HK1 Engine Workshop Manual

Quick summary (what this guide covers)
- Theory: how a common-rail diesel fuel system on Isuzu 4HK1 / 6HK1 engines works, why pumps fail, and what can go wrong.
- Detailed component descriptions (every relevant part of the fuel system).
- Tools, safety and parts list.
- Step‑by‑step workshop procedure for replacing:
1) the low‑pressure (lift) pump (in‑tank or in‑line), and
2) the high‑pressure fuel pump (HPFP / common‑rail pump).
- Bleeding/priming, testing and troubleshooting.
Read fully before starting. This guide assumes no prior experience but does not replace the OEM workshop manual. Consult the official manual for exact torque figures, model variants, and electronic procedures.

THEORY — how the system works (simple analogies)
- Think of the fuel system as the engine’s circulatory system. The fuel tank is a reservoir, the low‑pressure lift pump is the heart’s pacer that gets fluid moving, the fuel filter/water separator is the kidney that cleans it, the high‑pressure pump (HPFP) is the left ventricle that produces the high pressure, and the common rail is the arteries that feed injectors (capillaries).
- Sequence: fuel flows from tank → lift pump → primary/secondary filters (water separator) → low‑pressure feed line → high‑pressure pump → common rail → injectors → return lines back to tank.
- Why replacement is needed: pumps wear out (mechanical wear, seized vanes, failed diaphragms, bearings, electrical motor failure), get contaminated by dirt/water, or develop leaks. Symptoms include hard starting, no start, rough idle, poor power, fuel pressure faults, long cranking, and visible leaks.
- What can go wrong if left: air ingestion (loss of pressure), rail pressure low or fluctuating (engine runs poorly), metal debris from a failing pump damaging injectors or HPFP, leaks causing fire risk.

DETAILED COMPONENTS (what each part is and what it does)
- Fuel tank: stores diesel. Has pickup and sometimes an in‑tank pump and return line.
- Low‑pressure (lift) pump:
- In‑tank electric pump — submersible; usually an assembly with strainer, pump motor, and fuel level sender.
- Inline/electric lift pump — mounted on chassis or engine; electric motor with inlet and outlet ports.
- Function: move fuel from tank to filter and HPFP at low pressure (generally <1 bar).
- Strainer (sock): coarse mesh at tank pickup to stop large debris entering pump.
- Fuel filter / water separator:
- Primary/coarse filter and a water trap. Removes water and particulates; has drain/bleed screw and sometimes a sensor.
- Fuel heater (if fitted): warms fuel in cold climates.
- Feed/return fuel lines: flexible or hard lines that carry fuel; banjo joints, compression fittings, and quick‑disconnects.
- Fuel pressure sensor (low‑ and high‑pressure): measures pressure in feed lines or common rail and reports to ECU.
- High‑pressure fuel pump (HPFP / common‑rail pump):
- Mechanically or gear/cam driven pump that compresses fuel to injection pressure (1000s of bar on modern systems).
- Contains plungers, cam plate, delivery valves, timing provisions, and sometimes a vacuum or oil lubrication feed.
- Often has a timing position relative to camshaft and may require special procedures for removal/installation.
- Common rail: an accumulator (steel tube) that stores high‑pressure fuel, distributing it to injectors.
- Injectors: atomize fuel into cylinders at controlled timing/quantity.
- Pressure relief / overflow / return lines: return excess fuel to tank. Also relieve overpressure.
- Fuel shut‑off solenoid: cuts fuel when engine stops/ECU commands.
- Bleed screw / priming pump (manual): used to evacuate air from the low‑pressure side.
- Seals, O‑rings, copper washers, banjo bolts: ensure leak‑free joints.

TOOLS & PARTS (basic workshop list)
- Safety: gloves (nitrile), safety glasses, shop rags, drip pan, absorbent pads, fire extinguisher (class B), good ventilation, no smoking.
- Tools: metric socket set, torque wrench, open/box/flare/line wrenches (for fuel lines), screwdrivers, pliers, pick set for O‑rings, hammer and punch (sometimes), Allen/hex keys, feeler gauge (if timing), timing mark tools if needed, multimeter.
- Special tools recommended: fuel line disconnect tool (quick disconnects), HPFP timing holder (if required by engine), diagnostic tool (to read fuel pressure and faults), injector line torque/cleaning tools.
- Consumables & spares: new pump (correct part number), new filter(s), new O‑rings/copper crush washers for banjo bolts, threadlocker (if specified), clean diesel for priming, anti‑seize, fuel‑rated lubricant, replacement clamps and hose where needed.

SAFETY & PREPARATION
- Work in a well‑ventilated area, no open flames or sparks, battery negative disconnected before working on fuel electrical connectors.
- Have absorbents and a container to capture fuel. Diesel spills make slippery surfaces and are flammable.
- Relieve system pressure before opening any fuel lines (see bleeding section).
- Keep everything very clean. Contamination will damage injectors and the HPFP.
- Plan for staging: label hoses, brace components, take photos for reassembly.

DIAGNOSIS — when to replace the pump
- Symptoms suggesting low‑pressure pump failure:
- Long cranking or no start but starter turns.
- Audible failure: submersible pump not humming or inline pump silent.
- Low feed pressure at HPFP inlet (use gauge).
- Fuel system fault codes for low supply pressure or fuel pump circuit faults.
- Visible leaks, smoke from pump, burnt smell.
- Symptoms for HPFP failure:
- High‑pressure fault codes (rail pressure low, low pressure cutout).
- Engine starts then dies or has no power.
- Excessive metal particles in filter or on magnet in filter head.
- Oil contamination in pump (if lubrication shared) or unusual noises.

PROCEDURE A — Replacing the Low‑Pressure (Lift) Pump (inline or in‑tank)
Note: If in‑tank, this is slightly different (drop the tank or remove access cover). Below covers both types in general terms.

1) Preparation
- Disconnect negative battery. Wear PPE.
- Relieve fuel system pressure: cycle ignition to ON a few times to vent pressure, or use specified bleed procedure. For in‑tank pumps, opening a downstream line may let pressure escape—capture fuel.

2) Access & isolation
- If in‑tank: remove tank straps or access cover; support the tank. If inline: locate pump on chassis or engine.
- Label electrical connectors and hoses. Take photos.
- Place drip pan under work area.

3) Disconnect electrical and fuel lines
- Unplug electrical connector from pump.
- Using flare/line wrenches or appropriate disconnect tools, remove inlet and outlet fuel lines. Cap lines to avoid contamination.
- For in‑tank: disconnect fuel sender harness, vent hoses, and any fuel lines at the pump module. Remove retaining ring or bolts on top of tank and lift assembly out carefully—the float arm is fragile.

4) Remove pump
- Remove mounting bolts and take pump out. Note any brackets or spacers.
- Inspect lines, clamps, and wiring for corrosion; replace if needed.

5) Install new pump
- Compare old/new pump; transfer any brackets or fittings if required.
- Replace O‑rings, crush washers, and any seals. Never reuse copper washers or O‑rings.
- Mount pump, torque bolts to OEM spec.
- Reconnect fuel lines and electrical connectors.

6) Prime & bleed
- If there’s a manual priming pump, operate until fuel flows and no air.
- Reconnect battery negative.
- Turn key to ON (not start) to allow electric pump to run and pressurize low side; cycle several times to purge air.
- Crack bleed screws on filter or pump (if fitted) until pure fuel without bubbles appears; tighten after.
- Start engine and monitor for leaks and steady fuel supply.

Procedure Note: For in‑tank pumps, ensure the strainer (sock) is clean and seated properly to avoid suction issues.

PROCEDURE B — Replacing the High‑Pressure Fuel Pump (HPFP)
Important: HPFP removal may affect engine timing or synchronization in some engines. The HPFP is a precision component. If the HPFP is driven by camshaft/timing gear, proper locking of timing components and timing marks are critical. When in doubt, have the engine at TDC and consult OEM manual. If the pump has an electronic control or angle sensor, special programming may be required.

1) Preparation and safety
- Disconnect battery negative.
- Relieve fuel pressure. For common‑rail, cycle ignition to ON to let ECU stop fuel and relieve rail pressure via injector control procedure or use bleed on filter head/rail until pressure is low. Follow OEM recommended depressurization to avoid fuel spray.
- Clean around the pump area thoroughly (dust & clean rags). Contamination leads to damage.

2) Remove obstructing components
- Remove air intake ducting, engine covers, alternator/support brackets or anything blocking access to HPFP.
- Remove any hose clamps, vacuum hoses, or wiring that obstruct access. Label and photo everything.

3) Disconnect fuel lines and electrical connectors
- Use line wrenches to loosen high‑pressure lines from HPFP. High‑pressure lines often use flared fittings or banjo bolts—support lines to avoid bending.
- Cap or plug lines immediately after removal to prevent contamination and fluid loss.
- Unplug electrical connectors (fuel pressure sensor, solenoid) from the pump.

4) Lock timing (if required)
- If pump timing is referenced to the cam/crank, lock cam and crank per manual. If a timing pin is used on the pump, align pump timing marks and use a holder to prevent rotation during removal.
- Failure to maintain timing may result in poor engine timing or damage to pump or engine.

5) Remove HPFP mounting bolts and lift pump
- Remove bolts in a steady pattern. The pump can be heavy—support it as you remove the last bolt to avoid sudden drop.
- Note orientation and position; many pumps have dowel pins or locator faces—these must match at reinstallation.

6) Inspect mating surfaces and components
- Check fuel line threads for damage, inspect delivery valve seating, and examine the drive coupling or gear.
- Replace any O‑rings, seals, and copper washers.

7) Install new HPFP
- Fit new pump using new seals. Slide carefully onto dowels or align properly.
- Torque mounting bolts in the sequence specified by OEM to the correct values.
- Reconnect HP fuel lines with new crush washers; torque banjo bolts to spec. Use a torque wrench—leak or rupture risk if under/over‑torqued.

8) Reconnect electricals and any removed brackets
- Reinstall any removed items in reverse order.

9) Bleed / prime the system (critical)
- Fill primary filter with clean diesel if required.
- Prime low‑pressure side first until fuel reaches the HPFP (use manual priming pump or key cycles).
- Use key ON cycles to allow the lift pump to fill the HPFP and rail. Many systems require multiple ON/OFF cycles and then cranking to purge air.
- Some engines require cranking with the starter (without starting) in repeated intervals to build rail pressure and purge air—observe OEM procedure. Do not exceed starter duty cycle limits.
- After low side primed, the ECU and HPFP will produce rail pressure; watch for fault codes.
- Use a diagnostic scanner to monitor rail pressure ramp and confirm correct pressure. Some HPFP replacements require calibration or ECU adaptation with dealer tools.

10) Start & test
- Start engine, idle for several minutes, watch for leaks, listen for unusual noises.
- Check rail pressure under idle and load with a gauge or scan tool. Test drive and monitor acceleration and response.
- Re‑check for leaks and retorque fuel fittings after warm‑up.

COMMON PROBLEMS & HOW TO AVOID THEM
- Air in system: causes hard starting, rough idle. Prevent by keeping lines upright and seals tight, bleeding thoroughly.
- Contamination (dirt/water): new pump can be ruined by dirty fuel or contaminated lines. Always clean work area, replace filters, and use clean containers.
- Reusing O‑rings/washers: leads to leaks. Always replace.
- Damaging banjo fittings or over‑torquing: use specified torque. Over‑torque crushes washers or threads; under‑torque leaks.
- Incorrect timing/installation of HPFP: can cause poor performance or damage. Lock timing if required and follow OEM timing instructions.
- Electrical faults: check wiring and connectors; failing to reconnect ground or power can cause no‑run conditions or codes.
- Not priming: causes poor start; may allow pump to cavitate and overheat.

TESTS TO PERFORM AFTER REPLACEMENT
- Visual leak check under pressure and after warm‑up.
- Low‑pressure feed test: measure inlet pressure to HPFP using gauge and compare to OEM spec.
- Rail pressure test: use scan tool or gauge to confirm rail pressure at idle and under load.
- Electrical test: verify pump motor voltage, continuity and solenoid operation if applicable.
- Scan for codes: clear and re‑verify that no fuel supply or pressure codes return after test drive.

TROUBLESHOOTING QUICK GUIDE
- No crank/no start: battery? starter? fuel cutoff? Check fuel pump power circuit and fuses.
- Cranks but won’t start: low rail pressure (HPFP issue) or air in system. Check pump operation, pressure sensor, and bleeding.
- Starts then dies: possibly leak or check valve failure or air ingestion. Inspect return lines and injectors.
- Poor power or surge: HPFP delivery issues, injector problems or clogged filter — check filter and pressure stability.
- Leaks at fittings: tighten to spec, replace washers if leaking, clean and reassemble.

FINAL TIPS (practical, workshop-aware)
- Always replace the fuel filter(s) whenever you replace a pump — dirty filter often the cause of pump failure.
- Use only OEM or quality aftermarket pumps and correct part numbers.
- Keep joints and lines capped during the job; contamination is the most common cause of post‑repair failures.
- If the HPFP requires calibration, use dealer diagnostic tools or have the pump installed and calibrated by a qualified shop.
- Take photos at each step for reassembly. Label hoses and connectors.
- After work, properly dispose of used fuel, filters, and contaminated rags.

CONCLUSION
Replacing the lift pump is a straightforward electrical/mechanical job for a beginner if you follow safety steps and bleeding procedures. Replacing the HPFP is more complex: cleanliness, correct alignment/timing, and precise torqueing matter. If you cannot access the OEM torque figures or timing/procedures for your engine serial number, or if the HPFP requires ECU reprogramming, get a shop or dealer to complete or verify the work.

No yapping — done.
rteeqp73

Hitachi ZX-3 Diagnostics Menu This was shot some time ago next to a project. I wanted more video but not going to get it soon so I made a short program.

Brand new Isuzu 6BG1 complete engine for HITACHI excavator ZX200 ZX200-3G Brand new Isuzu 6BG1 complete engine for HITACHI excavator ZX200 ZX200-3G CC-6BG1.

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Short version: the water pump is the engine’s coolant “heart.” Replacing it on Isuzu 4HK1 / 6HK1 engines involves draining coolant, removing drive accessories and any timing/front cover items that block access, removing the pump, fitting a new pump with correct seal/gasket and correct fastener torques, reassembling, refilling and properly bleeding the cooling system, then test-running and checking for leaks and correct temperature. Below is an expanded, beginner-friendly workshop-style guide with component descriptions, how the system works, common failure modes and a step‑by‑step procedure. Read it fully before starting. Always use the OEM workshop manual for exact bolt torques, timing marks and model‑specific steps.

Why this repair is needed (theory, simple analogy)
- Analogy: coolant circulation is like the human circulatory system. The water pump is the heart, the radiator is the lungs, hoses are blood vessels, and the thermostat is a temperature‑controlled valve. If the heart fails the “blood” (coolant) stops circulating properly and the engine overheats.
- Purpose: the pump forces coolant through the engine block, cylinder head, heater core and radiator so heat generated by combustion is carried away and dissipated.
- How it works: inside the pump housing an impeller (blades) spins on a shaft. The spinning impeller creates flow (centrifugal pump action), drawing coolant from the radiator/expansion tank and pushing it into engine coolant passages. The pump shaft is supported by bearings and sealed where it passes through the housing by mechanical seals—these keep coolant inside while the shaft rotates.
- Drive methods: water pumps are driven either by accessory belts (V‑belt or serpentine), by a timing belt/chain or gears on diesel engines. On many Isuzu 4HK1/6HK1 applications the pump can be driven by front accessory belt or may be integrated into the timing/front cover—verify your exact model.
- Why they fail: bearing wear, seal failure, impeller corrosion or damage, cavitation, contamination, electrolysis, or external gasket/pipe leaks. When bearings fail you may hear whining/grinding; when seals fail coolant leaks externally or through the weep hole; corrosion/cavitation reduces flow and causes overheating.

Main components — what each is and why it matters
- Pump housing: cast aluminium/iron case that mounts to the engine and contains the impeller and mechanical seal. It provides coolant ports and bolt bosses.
- Impeller: the spinning blades inside the housing that move coolant. Can be metal or composite. Damaged or eroded impellers greatly reduce flow.
- Shaft: connects impeller to the drive (pulley or gear). Must be straight and free of play.
- Bearings: radial bearings support the shaft. When worn you get axial/radial play and noise.
- Mechanical seal (shaft seal): usually a spring-loaded ceramic/graphite seal that prevents coolant passing along the shaft. When it fails it leaks. Many pumps have a “weep hole” to show internal seal failure by dripping coolant externally.
- Pulley or drive flange: attaches to the pump shaft so the engine can drive the impeller.
- Gasket / O‑ring: seals the pump housing to the block or cover to prevent coolant leaks. Use correct gasket material, clean surfaces and do not over‑use sealant unless specified.
- Mounting bolts: secure the pump to the block/front cover. Threads and length vary; some may be studs.
- Hoses and connections: inlet and outlet hoses, heater hoses and bypass passages connect to the pump. Clamps must seal.
- Thermostat (related): controls coolant flow to radiator. Often replaced at same time if high mileage or when pump fails.
- Fan, fan clutch, shroud (if applicable): may need removal to access pump. Ensure fan removal is done safely.
- Timing cover / timing components (if applicable): if pump is behind timing assembly, removal and correct timing reassembly is critical.
- Coolant temperature sensor / switch (nearby): check when reassembling; do not damage connectors.

Common symptoms of a failing water pump
- External coolant leak at pump area (visible puddle or dried coolant residue).
- Overheating under load or at idle.
- Unusual whining/grinding noise from front of engine (bearing failure).
- Steam from engine bay or persistent low coolant level.
- Reduced heater output (no or little warm air).
- Coolant contamination (metal particles, rust) in housing.
- Visible impeller damage if inspected.

Tools and consumables you will need (basic list)
- Service/repair manual for your exact 4HK1/6HK1 model (torques, diagrams, timing marks).
- Basic hand tools: metric socket set, wrenches, extensions, breaker bar.
- Torque wrench (essential).
- Screwdrivers, pliers (hose & spring pliers).
- Drain pan.
- Gasket scraper / plastic scraper and clean rags.
- Wire brush, solvent/degreaser.
- New water pump (OEM or high‑quality aftermarket), new gasket(s)/O‑ring(s).
- New thermostat if recommended (good practice).
- New hose clamps if old ones are corroded.
- Coolant (correct type/mixture per Isuzu spec).
- Sealant if the manual specifies (use correct type — typically a non-hardening RTV where directed).
- Pulley/gear puller if pulley is pressed on.
- Belt tensioner tool or method to remove belts.
- Safety: gloves, safety glasses, jack and jack stands if you must raise vehicle.

Safety and prework notes (don’t skip these)
- Work on a cold engine. Hot coolant causes severe burns.
- Disconnect negative battery if you’ll be working near electrical components.
- If fan is mechanical/viscous and engine may be started, ensure fan is secured before rotating by hand—fans can have sharp blades and store energy.
- If the pump is behind the timing cover, you are working on critical engine timing. You must mark and reassemble timing exactly. If unsure, get help or consult a professional.
- Catch and properly dispose of used coolant.

General step‑by‑step procedure (model variations exist — follow your manual)

Preparation
1. Park on level ground, set parking brake, chock wheels. Allow engine to cool completely.
2. Remove engine cover / cowling if present so you have room.
3. Place drain pan under radiator drain. Open radiator cap to allow draining and open drain cock or remove lower radiator hose to drain coolant. Dispose or recycle coolant properly.

Access and removal
4. Remove obstructions to pump: depending on model, remove fan and fan shroud, drive belts (serpentine or V belts), alternator bracket or other accessories blocking access. Note belt routing or take a photo for reinstall.
5. If the pump is belt driven: loosen tensioner, relieve belt tension and remove belt(s). If pump is behind timing gear: remove timing cover according to manual and mark timing positions before removing any timing components.
6. Inspect and remove any hoses connected to the pump (clamps may be spring type or screw type). Take care to catch remaining coolant.
7. Remove pump mounting bolts in a crisscross pattern if accessible. Keep bolts organized by location. Remove pump from engine. If it’s stuck, a few light taps (not hitting the impeller) or penetrating oil can help—do not pry on gasket surfaces in a way that damages mating surfaces.
8. Inspect removed pump: check for bearing play (rock the pulley/shaft), listen for roughness by hand‑spinning, look at impeller for corrosion or damage, look for wetness at weep hole. These confirm failure modes.

Surface prep and new pump inspection
9. Clean mating surfaces on the block/cover. Remove old gasket material with a plastic scraper and solvent. Do not gouge or damage faces. Check bolt holes for thread damage.
10. Compare new pump to old pump: check port alignment, bolt pattern, gasket type, impeller direction and pulley fit. Ensure new pump is identical.
11. If manual requires new O‑ring/gasket application or a bead of sealant, follow manual. If a thin coat of RTV is required at specific corners, use only manufacturer specified product and allow proper cure time where necessary.

Installation
12. Fit new gasket / O‑ring as instructed. Lightly coat mating surfaces with coolant or anti‑seize if specified (do not overuse sealant). Position pump carefully and start mounting bolts by hand to avoid cross‑threading.
13. Tighten bolts in a crisscross/sequence to the specified torque in the workshop manual. Do not over‑tighten — this crushes gaskets and can warp housing. If you do not have manual torque values, obtain them before proceeding.
14. Reinstall hoses and clamps. Replace hose clamps if corroded. Reinstall belts and tension to spec or use belt tensioner tool. If the pump was driven by timing components, reassemble timing marks exactly and replace timing belt/chain if worn or if manual recommends replacement when pump is removed.
15. Reinstall fan, fan clutch, shroud, alternator brackets and any accessories removed. Ensure fan bolts are torqued and fan rotates freely by hand.

Refill and bleed
16. Refill cooling system with the correct coolant/water mix and bleed air. Bleeding procedure varies:
- Some systems have a bleed screw at a high point. Open it while filling until coolant flows without air.
- Run the engine with heater on high and the radiator cap off (or follow manual) until thermostat opens and coolant circulates; top up as air escapes.
- Squeeze heater hoses (carefully) to move trapped air.
- On some diesels with pressurized reservoir, use the proper filling/bleeding method in the manual.
17. Confirm coolant level in overflow/tank once engine cools after test run.

Test and verify
18. Start engine and observe for leaks around the pump and hose connections with a flashlight. Listen for abnormal noises (bearing whine, knocking).
19. Monitor temperature gauge and ensure engine reaches and holds normal operating temperature. Check heater output to confirm circulation.
20. After drive cycle and cool down, recheck coolant level and retorque any suspect bolts per manual if required.

Common pitfalls & troubleshooting (what can go wrong and how to avoid it)
- Not replacing the thermostat when pump fails: if thermostat is sticking it can cause overheating even with a new pump. Consider replacing both.
- Air pockets in the system: air reduces coolant flow and causes overheating. Bleed per OEM procedure.
- Incorrect torque/over‑tightening bolts: can crack housing or warp mating surface causing leaks. Use a torque wrench and the manual.
- Reusing old gasket or using too much sealant: use the correct new gasket and only the type of sealant the manual specifies.
- Not replacing or inspecting belts, idlers and tensioners: worn tensioners or misaligned pulleys shorten pump life and cause noise.
- Not checking impeller direction or replacement pump fit: a wrong pump will circulate poorly or not fit.
- Damaging electrical connectors or sensors: keep connectors clean and secure.
- Disturbing timing without marking: if the pump removal required removing timing components, improper reassembly can cause catastrophic engine damage. Use manual and set timing marks precisely.
- Electrolysis/corrosion: if engine has signs of electrochemical corrosion, investigate causes (bad earths, wrong coolant) before new pump fails prematurely.

Signs to replace other parts at same time (good workshop practice)
- Replace thermostat, belts, belt tensioner/idler bearings if worn, and possibly hoses and clamps.
- If timing belt/chain removed, replace it and the tensioner/idler as recommended by the manual.

Final checklist before leaving the job
- No coolant leaks at pump, hoses, radiator or heater connections.
- Correct coolant level and no air in system (heater works and temperature is stable).
- No abnormal noises from pump area.
- Belts routed and tensioned correctly.
- Fasteners torqued to spec and tools removed from engine bay.
- Clean up spilled coolant and dispose of used coolant properly.

When to get professional help
- The pump is behind the timing gears/chain and you lack experience setting engine timing.
- You see engine timing marks misaligned and are unsure how to proceed.
- Significant corrosion, stripped bolt threads, or broken studs that require helicoil or special repair.
- You are uncomfortable with welding, machining, or specialty pulling/pressing tools that some removals require.

Closing practical tips
- Photograph every step and label parts/belts as you remove them — it saves time when reassembling.
- Work methodically and keep like bolts together.
- Buy a quality replacement pump (OEM or a reputable brand) and the correct gasket set.
- Keep the workshop manual handy — it contains essential torque values, sequences and model‑specific notes that must be followed.

That’s the full beginner‑level workshop approach. Follow the model‑specific workshop manual for exact bolt torques, timing mark locations and any special procedures for your Isuzu 4HK1 or 6HK1 variant.
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