KANGDA 2Q78 / BH2Q85R8 – Fuel Injection Pump For YC2105D Diesel Engine

When a YC2105D engine loses pulling power or emits excessive black smoke under load, the fuel injection pump often bears the blame. This KANGDA assembly (Order 2Q78, Model BH2Q85R8) directly replaces the original unit fitted to Yuchai's 28 kW industrial workhorse, restoring the precise fuel delivery that these two-cylinder diesels demand at their rated 2400 RPM operating speed. No electronic diagnostics or reprogramming are required – just mechanical fitment and timed calibration.

Machined to Yuchai's factory blueprint, this pump carries a plunger diameter grouped as 8.5 mm, with the cam lift profile ground to match the YC2105D's combustion chamber design. The delivery valve holder, outlet fitting thread, and drive gear pilot diameter all replicate OE specifications, meaning existing high-pressure lines and mounting brackets stay intact. Order number 2Q78 cross-references directly to the Yuchai parts catalogue, while the BH2Q85R8 head assembly determines the start-of-delivery point relative to crankshaft position. Governor spring rates are pre-set for the 28 kW output ceiling, with the speed control mechanism calibrated to maintain stable idle down to 650 RPM without hunting.

Beyond stationary generators, this pump sees regular service in agricultural power units, road compaction rollers, and small marine auxiliary engines that rely on the YC2105D's compact footprint. The mechanical governor responds to load changes without electronic intervention – a trait valued in remote job sites where sensor failures strand modern engines. Fleet operators running multiple Yuchai-powered machines appreciate having a standardized spare that fits across different equipment brands, as long as the base engine remains the YC2105D variant. This interchangeability reduces the number of unique part numbers that workshops must keep on the shelf.

Fitment begins by locking the engine at top dead centre on the compression stroke for cylinder one. Align the scribe mark on the pump drive gear with the stationary pointer cast into the timing cover – this step directly influences ignition delay. Mount the pump using the original shims; their combined thickness sets the plunger pre-stroke and must not be altered arbitrarily. After snugging the retaining nuts to the specified torque range, prime the fuel system by operating the hand lever on the lift pump until bubble-free diesel emerges from the vent plug. Crank the engine without starting for several revolutions to distribute fuel internally, then fire it up and observe the exhaust – a clean haze indicates correct timing, while persistent white smoke suggests further adjustment of the shim pack.

Although common-rail architectures dominate highway trucking, the YC2105D's inline pump remains vulnerable to specific failure triggers. Water carryover from contaminated storage tanks attacks the plunger and barrel lapped faces, producing microscopic pitting that bleeds injection pressure and retards effective timing. Diesel with low cetane number or poor lubricity accelerates scuffing on the cam roller and tappet surfaces – wear that manifests as uneven cylinder firing at low speed. For repair workshops, replacing a compromised pump with this KANGDA unit eliminates guesswork associated with rebuilding worn cores, where bore ovality often goes undetected without specialised measuring equipment. The BH2Q85R8's hardened alloy construction offers improved resistance to these degradation mechanisms, contributing to longer intervals between overhauls when paired with proper fuel management practices.

Q1: Is this pump compatible with YC2105D engines that have been converted to electric start or different flywheel housings?
A: Yes, the pump mounts independently of starter motor configuration. Only the drive gear engagement and timing marks matter – external accessories do not affect fitment.

Q2: How should the pump be stored if kept as a contingency spare for a remote site?
A: Keep it in its original packaging with desiccant bags. Rotate the drive shaft periodically by hand to redistribute internal lubricant and prevent plunger sticking.

Q3: Will replacing this pump with the KANGDA unit require changing the injector nozzles as well?
A: Not necessarily. However, if the old nozzles show carbon fouling or uneven spray patterns, pairing new nozzles with the new pump delivers the best combustion results.

Q4: What is the recommended torque for the high-pressure line nuts on this pump?
A: Tighten to 30–35 N·m using a crowfoot wrench. Over-torquing deforms the ferrule and creates internal restrictions that mimic pump wear.

Q5: Does KANGDA offer a core exchange programme for worn-out 2Q78 pumps?
A: Core return policies vary by distributor. Inquire with your supplier about potential credits for rebuildable cores – many accept them for remanufacturing.