Part of the Yanmar Parts Manuals.
Strip a Yanmar 4TN78TL down to the bare block and every liner, bearing shell, and gasket you pull off has a factory part number this catalog puts in front of you. Yanmar publication Y00B3631 covers the 4TN78TL-DBVM, 4TN78TL-DB, and 4TN78TL-RB, including the K2094 designation, across 63 pages of exploded views and numbered parts lists.
When the engine is in pieces on a stand and there is nobody at a parts counter to ask, guessing at an O-ring or oil seal is how a rebuild stalls for a week. Each of the 30 sections, from Cylinder Block and Cylinder Head through the Fuel Injection Pump to the Starting Motor and Generator, pairs a diagram with exact factory numbers so you order everything once.
Bookmarked sections take you from the part in your hand to its listing in a couple of clicks, whether this engine sits in a genset, a pump, a boat, or on your bench.
What's Inside This Yanmar 4TN78TL-DB / RB / DBVM (K2094) Parts Manual
| System | Pages | Key Topics |
|---|---|---|
| Cylinder Block | 2-3 | Cylinder Block Assy, Main Bearing, Thrust Bearing, Camshaft Bush, Cylinder Head Gasket, Cylinder Liner, Cylinder Sleeve, Check Valve Assy |
| Gear Housing | 4-5 | Gears w/ Seal Housing, Oil Seal, Lub. Oil Supply Cap, Gear Housing Flange, Gears Housing Flange, Hydraulic Oil Pump Cover, Hydraulic Oil Pump Gasket, Gasket |
| Flywheel Housing | 6-7 | Flywheel Cover Cap, Pin, Bolt |
| Lub.Oil Sump | 8-9 | Lub. Oil Sump Assy, Oil Sump, Knock Pipe, Oil Sump Cover Gasket |
| Oil Seal Housing | 10-11 | Oil Seal Case Assy, Oil Seal, Oil Seal Case Gasket, Pin |
| Bonnet | 12-13 | Bonnet Assy, Bonnet Gasket, Breather Cover Assy, Shelter Plate, Breather Baffle, Lub. Oil Supply Cap, Knob, Breather Pipe |
| Gear Housing Cover | 14-15 | Hydraulic Oil Pump Cover, Cover, Hydraulic Oil Pump Gasket, Round Gasket 8, Blind Cover |
| Cylinder Head | 16-17 | Cylinder Head Assy, Valve Guide, Intake Valve, Exhaust Valve, Valve Spring, Spring Retainer, Valve Stem Seal, Valve Cap |
| Air Cleaner | 18-19 | Intake Pipe, Air Cleaner Assy, Cover, Air Cleaner Element, Indicator, Unloader Valve, Air Cleaner Bracket, Rubber Seat |
| Exhaust Manifold | 20-21 | Exhaust Manifold Gasket, Bolt, Stud |
| Camshaft | 22-23 | Camshaft Assy, Camshaft Gear, Thrust Bearing, Tappet, Push Rod |
| Turbocharger | 24-25 | RHB31 Turbo Charger, Heat Protector, Hose, Turbo Rotor Assy, Blower Housing Assy, Turbo Housing Assy, Housing Assy, Control Assy |
| Crankshaft & Flywheel | 26-27 | Crankshaft Assy, Crankshaft Gear, V-pulley, Flywheel Assy, Ring Gear |
| Piston | 28-29 | Piston Assy, Ring Set, Piston w/ Ring 0.25, Pin |
| Connecting Rod | 30-31 | Connecting Rod Assy, Piston Pin Bush, Bolt, Pin |
| Idle Gear | 32-33 | Idle Shaft, Idle Gear Shaft, Idle Gear w/ Bush, Gear w/ Bush, Idle Gear Bush |
| Lub. Oil System | 34-35 | Lub. Oil Pump Assy, Lub. Oil Pump Gasket, Lub. Oil Cooler, Lub. Oil Dipstick, Dipstick Guide, Oil Strainer Gasket, Gasket, Oil Inlet Pipe |
| Lub.Oil Line | 36-37 | Check Valve, Oil Pressure Switch, Lub. Oil Pipe Assy, Round Gasket 10, Retainer 8X 8, Retainer, Pipe Joint PT3/8, Lub. Oil Return Pipe |
| Cooling Water System | 38-39 | Cooling Water Pump Assy, Cooling Water Pump Gasket, Elbow, Elbow PT1/4, V-belt, V-pulley, Cooling Fan, Spacer |
| Fuel Injection Pump | 40-42 | Pump w/ Governor & Feed Pump, Camshaft, Thrust Ball Bearing, Bearing Retainer, Plunger w/ Barrel, Retainer A, Plunger Spring Shoe, Plunger Spring |
| Fuel Injection Valve | 43-44 | Fuel Injection Valve Assy, Fuel Injection Nozzle Assy, Nozzle Holder Assy, Nozzle Spring, Nozzle Spring Seat, Stop Plate |
| Fuel Injection Pipe | 45-46 | Retainer, Bolt |
| Fuel Strainer & Fuel Line | 47-48 | Pipe Joint 12, Gasket 12, Fuel Pipe, Fuel Strainer Assy, Taper Valve, Taper Valve Spring, Lever, Strainer Cup |
| Fuel Return Line | 49-50 | Pipe Joint 12, Joint, Fuel Pipe, Fuel Return Pipe, Cap, Check Valve Assy, Round Gasket 12 |
| Governor | 51-52 | Governor Case, Governor Case Gasket, Governor Case Cover, Case Cover Gasket, Link 0, Control Lever, Governor Lever Shaft, Governor Lever Assy |
| Starting Motor | 53-54 | Starter, Pinion Stopper Set, Pinion Stopper Clip, Field Coil Assy, Pore Core Screw Set, Brush, Rear Cover Assy, Rear Cover Metal |
| Generator | 55-56 | Rotor Assy, Spacer, Stator Assy, Rear Cover Assy, Regulator Brush Assy, Brush Assy, Regulator Assy |
| Magnetic Relay | 57-58 | Earth Cord, Cord, Bolt |
| Tropics & Desert Type (Option) | 59-60 | Dust Filter, Air Cleaner Assy, Outer Element, Cleaner Body, Air Cleaner Cup, Baffle, Inner Element, Unloader Valve |
| Gasket Set & Tool (Option) | 61-63 | Gasket Set, Cylinder Head Gasket, Hydraulic Oil Pump Gasket, Oil Sump Cover Gasket, Oil Seal Case Gasket, Bonnet Gasket, Suction Manifold Gasket, Exhaust Manifold Gasket |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Spring Pin Dimensions | 3x10 mm | p. 2 |
| Key Dimensions | 7x14 mm | p. 22 |
| V-Belt Type | A-38 | p. 38 |
Yanmar 4TN78TL-DB / RB / DBVM (K2094) Common Problems This Manual Covers
Turbo oil seals weeping into the intake
Oil smoke under load and a slick film inside the intake tract point to worn turbo seals. The Turbocharger section lists the rotor assembly, housing assembly, seal plate assembly, and a complete overhaul kit by part number.
Manual Section: Turbocharger p. 24Hard starting and rough uneven running
Worn plungers and delivery valves in the injection pump make a 4TN78TL slow to light off and lumpy at idle. The Fuel Injection Pump section breaks the pump down to plunger with barrel, delivery valve, tappet assembly, and control rack level.
Manual Section: Fuel Injection Pump p. 40Smoky exhaust from tired injector nozzles
Dribbling nozzles smoke under load and wash fuel past the rings. The Fuel Injection Valve section identifies the complete injection valve assembly, nozzle assembly, and holder assembly so you can renew all four in one order.
Manual Section: Fuel Injection Valve p. 43Overheating from cooling system wear
A tired water pump, stuck thermostat, or worn V-belt will cook this engine no matter what it is installed in. The Cooling Water System section carries factory numbers for the pump assembly, thermostat, cooling fan, and the listed V-belts.
Manual Section: Cooling Water System p. 38Low oil pressure at operating temperature
Before condemning the bearings, price out the cheaper suspects. The Lub. Oil System section lists the oil pump assembly, cooler, strainer, filter, and dipstick by part number so you can work through them in order.
Manual Section: Lub. Oil System p. 34Starter drags or fails to engage
Brushes, field coil, and pinion wear out long before the armature does. The Starting Motor section itemizes the starter down to the brush, field coil assembly, pinion, and armature assembly, so a rebuild beats a whole new unit.
Manual Section: Starting Motor p. 53Frequently Asked Questions
Which engine models does this parts catalog cover?
It covers the Yanmar 4TN78TL-DBVM, 4TN78TL-DB, and 4TN78TL-RB, listed under the K2094 designation, as Yanmar publication Y00B3631. Parts are organized by system across 30 sections, from Cylinder Block to the optional Gasket Set & Tool listing.
Does it include torque specs or rebuild procedures?
No. This is a parts catalog: exploded diagrams with factory part numbers for identifying and ordering components, from the Cylinder Block through the Governor and Generator. For clearances and torque sequences, pair it with the service manual.
Can I find turbocharger rebuild parts in it?
Yes. The Turbocharger section lists the rotor assembly, housing assembly, control assembly, seal plate assembly, and a complete overhaul kit, so you can order the kit instead of chasing seals one at a time. p. 24
Are gasket sets and special tools listed?
Yes. The Gasket Set & Tool section, an option listing, covers the gasket set including the cylinder head gasket, O-rings, and oil sump cover gasket, which is the clean way to reseal the engine during reassembly. p. 61
Is this Yanmar 4TN78TL-DBVM manual a PDF I download?
You get a 63-page searchable PDF (1 MB) that downloads instantly after checkout. Open it on your laptop, tablet, or phone, and bring it right to the shop floor.
Is this Yanmar 4TN78TL-DBVM manual print-friendly?
Absolutely. No DRM or copy protection. Print the whole manual or just the pages you need. Any home or office printer works.
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