Applicable scope: use this procedure only for Hino Dutro WU / XZU series vehicles that are fitted with spark‑ignition (coil‑on‑plug) engines. Many Dutro/XZU models are diesel and use glow plugs — those do NOT have ignition coils. If your truck is diesel, stop and service glow plugs/injectors per diesel procedure.

Tools & consumables
- Basic hand tools: 1/4" and 3/8" ratchets, 3/8" extension(s), swivel/universal joint.
- Sockets: 8mm, 10mm, 12mm (common coil bolt sizes); deep 16mm or 21mm spark plug socket with rubber insert (size depends on plug).
- Torque wrench (0–50 N·m range) with appropriate socket.
- Multimeter (digital) with ohms function for coil testing.
- Flat and Phillips screwdrivers, pick for connector tabs.
- Pliers (needle‑nose).
- Dielectric grease (silicone).
- Electrical contact cleaner.
- Clean shop rags, gloves, safety glasses.
- Replacement parts: OEM ignition coil(s) (or coil pack), coil boots/seals if separate, spark plugs (recommended whenever coil has failed or boots are old), mounting bolts if corroded/rounded.
- Optional: Anti‑seize (very light, only if recommended by plug maker), torque seal marker.

Safety & prep
1. Park on level ground, engage parking brake, chock wheels.
2. Engine cold. Hot engines = burned hands and brittle plastics.
3. Disconnect negative battery terminal to prevent arcing/ECU damage.
4. Wear eye protection and gloves.
5. Keep dirt away from plug holes: blow or brush loose debris before removing coils/plugs.

Step‑by‑step replacement
1. Remove access parts
- Remove engine cover / air intake resonator / top air duct as needed to expose coil packs. Use screwdriver or appropriate socket.
- Clean the area around coils with compressed air or brush to prevent debris falling into cylinders.

2. Identify and label connectors (if more than one coil)
- Although coil‑on‑plug coils are modular, label connectors or mark with tape to avoid mixing harness routing. (Not always necessary if looking at orientation.)

3. Disconnect electrical connector
- Depress the locking tab and pull the connector straight off. Use a pick or small flat to lift tab if stiff—don’t pry on wires.

4. Unbolt coil(s)
- Remove the retaining bolt(s) holding each coil using the appropriate socket (usually 8–10mm).
- Keep bolts and any spacers organized.

5. Remove coil
- Pull the coil straight up with a slight twisting motion to break the boot seal. Avoid pulling on the wiring.
- Inspect the coil boot and end for carbon tracking, oil, or a cracked boot.

6. Optional: remove and inspect/replace spark plug
- If replacing plugs or checking, use deep spark plug socket with extension and swivel if needed.
- Turn anticlockwise to remove. Inspect electrode and thread condition.
- Gap new plugs to OEM spec (consult manual). Replace plugs if fouled, oily, or beyond service interval.

7. Test old coil(s) (optional check)
- Using multimeter set to ohms: measure primary resistance across coil primary terminals (consult coil spec; typical coil‑on‑plug primary ~0.5–3 Ω, secondary 3k–15k Ω — check OEM).
- If values are out of spec or open, replace coil.
- Note: some modern coils are tested better with a dedicated oscilloscope or by scan tool showing misfires.

8. Prepare new coil(s) and plug(s)
- Lightly apply dielectric grease to inside of coil boot lip (thin film). This prevents moisture and eases removal — DO NOT overfill.
- If coils use O‑rings or seals, ensure they are fitted and lightly lubricated per OEM.

9. Install coil onto plug
- Seat coil straight down into plug well over the plug until fully seated.
- Refit the retaining bolt and tighten to spec. Typical coil mounting bolt torque: 6–12 N·m (50–106 in‑lb). If unknown, snug and then 1/4 turn—prefer low torque. Refer to workshop manual for exact torque.
- Reconnect electrical connector until it clicks.

10. Reassemble and final checks
- Repeat for each coil.
- Reinstall air intake components and engine cover.
- Reconnect negative battery terminal.
- Start engine and observe idle; scan for codes and watch for misfire (rough idle, check engine lamp). If misfire persists, re‑check connector seating and plug torque.

Tool use details / tips
- Ratchet + socket: use correct sized socket and extension to reach confined coil bolts. Use swivel joint where angle is awkward.
- Spark plug socket: rubber insert holds plug during removal/installation. Use extension to avoid cross‑threading; start by hand for first 2–3 turns.
- Torque wrench: set to specified value (or low torque range above). Tighten smoothly; when torque clicks, stop. Over‑torque can crack coil flange or strip head threads.
- Multimeter: disconnect coil connector. For primary resistance, probe the two small electrical pins; for secondary, probe tower to a primary pin if spec provided. If unsure, compare identical coils on other cylinders for relative condition.
- Contact cleaner: spray into connector and on pins if corroded; dry fully before reconnecting.

Common pitfalls & how to avoid them
- Pulling on wires: always pull the connector housing, not the harness.
- Damaging locking tabs: depress locking tab before prying. If broken, replace connector.
- Dirt into cylinder: clean area before removing coils/plugs; use compressed air.
- Over‑torquing coil bolts: causes cracked plastic coil housings — use torque wrench and low torque values.
- Cross‑threading spark plugs: always start by hand, then use socket.
- Forgetting to gap/replace plugs: old/wrong plugs cause coil failure; whenever coil fails, inspect and likely replace plugs and boots.
- Not replacing boots/O‑rings: worn boots allow misfires. Replace boots if cracked or hardened.
- Installing wrong coils: buy exact OEM part number or exact fit aftermarket; electrical differences can cause damage.
- Reinstalling battery while connectors loose: ensure all connectors fully seated before reconnecting battery to avoid arcing.

Replacement parts required
- Ignition coil(s): OEM Hino or equivalent fitment for your engine. Replace the failed coil; if one failed due to others being old, consider replacing all for consistency.
- Spark plugs: recommended replacement interval; replace if worn or if coil failure caused plug damage.
- Coil boots/seals: replace if separate from coil and showing wear.
- Mounting bolts: replace if rounded or corroded.

Final verification
- Use OBDII scanner to clear codes and watch for misfire counts. Road test under load, ensure smooth acceleration and no stumble.
- If problems persist after correct installation, diagnose ignition wiring harness, ECM, fuel/air issues, or compression problems.

End.
rteeqp73

Hino Truck, Brake/Clutch problem, Possible lack of Vacuum?? Thanks for watching Everyone! I dont think this vacuum pump is providing enough vacuum! Your advice would be appreciated!

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