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Autopapyrus · Higer KLQ6 (2024), Cummins/Yuchai Diesel
https://autopapyrus.com/guides/higer/klq6-series/fuel-injection-pump-drive-gear-tightening/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Higer KLQ6 (2024), Cummins/Yuchai Diesel: Fuel Injection Pump Drive Gear Tightening

On Cummins and Yuchai diesels fitted to KLQ6 buses, the fuel injection pump drive gear sits on the pump shaft either on a taper with a key and nut, or on a flange with three or four bolts. The exact tightening torque depends on the specific engine (series, power rating, pump type), and for this combination it is not documented in open sources, so below are the general principle and procedure. I will not give a figure from memory for your engine: a mistake here leads to shifted injection timing or the gear coming loose.

Difficulty: Medium Time: 1-2 hours (without removing the timing cover) Steps: 10 Tools: torque wrench (approx. 40-250 N·m (30-184 lb-ft) range), sockets matching the gear nut or bolts, gear holding tool or crankshaft lock, injection pump gear puller, degreaser, marker, thread locker if needed

Parts

2
  • 🔩 When disassembling, the injection pump gear lock washer or nut (if it is single-use) and the drive cover seal are usually replaced. Note: the injection pump gear, the gear hub, and the nut are separate items, so do not mix them up when ordering. Price of the fastener and seal kit varies
  • 🔩 the gear is sold separately, so confirm with your supplier

Step by step

10 steps
  1. Determine the mounting design. Remove the protective cover or inspection plug of the injection pump drive. If the gear is on a taper, it is held by a single center nut with a washer. If it is on a flange, it is held by bolts in slotted holes that allow the timing to be adjusted.
  2. Before any work, disconnect the battery ground and let the engine cool down. Relieve residual pressure with the hand primer pump if you are working near the fuel lines. If the system is Common Rail, do not loosen the high-pressure fuel lines while the engine is running or has just been stopped.
  3. Set the crankshaft to TDC of cylinder No. 1 using the marks on the pulley or flywheel. Use a marker to put reference marks on the injection pump gear, the idler gear, and the housing. The marks are mandatory: you will use them to restore the original timing.
  4. Lock the gear against rotation. Use the factory holding tool or lock, not a screwdriver in the teeth: the teeth are easily damaged, and the injection pump is not designed for impact loads on the shaft.
  5. If the gear sits on a taper, degrease the shaft taper and the mounting bore before tightening. Do not apply lubricant to the taper unless the service manual explicitly requires it. Seat the gear on the key and start the nut with the washer by hand.
  6. Tighten the fasteners with a torque wrench. For the center nut on the pump shaft, the torque is typically in the range of about 60-150 N·m (44-111 lb-ft), and for flange bolts about 20-50 N·m (15-37 lb-ft) (for the exact value for your engine, see the manufacturer's service manual). Tighten the flange bolts in a crisscross pattern in two or three passes. Do not use an impact wrench.
  7. If the service manual specifies a final angle tightening, do it using the mark. After tightening, do not tap the shaft and do not tighten "by feel."
  8. Check the marks: the gear must not have shifted relative to the reference marks. Turn the crankshaft two full revolutions by hand and check the TDC marks and the injection pump gear position again. The backlash in the mesh must be even, with no binding.
  9. Install the drive cover with a new seal, reconnect the battery, prime the fuel system, and start the engine. Listen for knocking, gear whine, or unstable idle, which point to shifted timing or incorrect tightening. Read fault codes with a diagnostic scanner, especially for the crankshaft and camshaft position sensors, and check for leaks.
  10. After 50-100 km of driving, stop with the engine cold and check the fastener torque again. If you replaced the gear or removed the injection pump and were not sure about the injection timing, it is better to have the timing checked and corrected at a repair shop with diagnostic equipment.

Common mistakes and warnings

  • Do not tighten the gear nut "by feel": under-tightening lets the gear slip on the taper, shear the key, and upset the injection timing, while over-tightening deforms the pump shaft and causes seal leaks. If you have no experience with the timing and injection pump drive on a bus diesel, or if the engine has Common Rail with high line pressure (about 1500-2000 bar), leave the work to a repair shop: even at lower pressure a fuel jet is dangerous to skin and eyes, and a timing error damages the engine.