Part of the Yanmar Parts Manuals.
A 3TNC78L-RKAH that cranks but will not fire almost always comes down to the fuel side, and the injection pump pages in this catalog break that assembly into plunger with barrel, delivery valve with seat, and tappet assembly, each carried under its own Yanmar part number. Guessing at those numbers is expensive: order the wrong nozzle assembly or bearing and you pay for the part twice and do the teardown twice.
This is Yanmar publication Y00B4192, the parts catalog for the 3TNC78L-RKAH (V2) diesel engine, 37 pages of exploded views spanning cylinder block, cylinder head, crankshaft and pistons, camshaft and gears, lubrication and cooling systems, governor, engine stop device, starting motor, and generator. It also lists 0.25 oversize main and crankpin bearings plus oversize pistons and ring sets for rebuild work.
The PDF downloads instantly and prints clean, so the pages you need can sit beside the parts tray and get dirty while the engine is apart.
What's Inside This Yanmar 3TNC78L-RKAH (V2), 3TNC78L-RKAH Parts Manual
| System | Pages | Key Topics |
|---|---|---|
| Cylinder Block | 3-4 | Gear Housing Assy, Oil Seal, Lub. Oil Supply Cap, Gears Housing Flange, Hydraulic Oil Pump Cover, Hydraulic Oil Pump Gasket, Gasket, Knock Pipe |
| Gear Housing | 5-6 | Flywheel Housing, Flywheel Cover Cap, Lub. Oil Sump Assy, Lub. Oil Sump Spacer, Oil Seal Case Assy, Oil Seal |
| Flywheel Housing & Lub. Oil Sump | 7-8 | Cylinder Head Assy, Suction Valve, Exhaust Valve, Valve Spring, Spring Retainer, Valve Stem Seal, Valve Cap, Rocker Support Assy |
| Cylinder Head & Bonnet | 9-10 | Suction Manifold Gasket, Gasket, Suction Manifold, Exhaust Manifold, Exhaust Manifold Gasket, Air Heater, Air Heater Gasket |
| Suction & Exhaust Manifold | 11-12 | Camshaft Assy, Camshaft Gear, Thrust Bearing, Tappet, Push Rod, Idle Gear Shaft, Gear W/ Bush, Idle Gear Bush |
| Camshaft & Driving Gear | 13-14 | Crankshaft Assy, Crankshaft Gear, Crankshaft V-Pulley, Flywheel W/ Gear, Flywheel W/ Ring Gear, Ring Gear, Piston W/ Rings, Ring Set |
| Crankshaft & Piston | 15-16 | Lub. Oil Pump Gasket, Oil Strainer Gasket, Gasket, Oil Inlet Pipe Assy, Strainer Bracket, Bracket Gasket, Filter 90X80L, Lub. Oil Pipe Assy |
| Lub. Oil System | 17-18 | Cooling Water Pump Assy, Cooling Water Pump Gasket, V-Belt, Cooling Water Pump V-Pulley, Fan D310, Thermo.cover Gasket, Gasket, Thermostat Gasket |
| Cooling Water System | 19-20 | Fuel Injection Pump Gear, Fuel I Pump Assy, Camshaft, Thrust Ball Bearing, Bearing Retainer, Plunger W/ Barrel, Retainer a, Plunger Spring Shoe |
| Fuel Injection Pump | 21-22 | Fuel Injection Valve Assy, Fuel Injection Nozzle Assy, Nozzle Holder Assy, Nozzle Spring, Nozzle Spring Seat, Stop Plate, Injection Pipe Retainer, Fuel Injection Pipe |
| Fuel Injection Device | 23-24 | Pipe Joint, Gasket, Fuel Pipe, Fuel Return Pipe, Joint, Cap, Check Valve Assy, Round Gasket |
| Fuel Line | 25-27 | Governor Case Gasket, Governor Case Cover, Case Cover Gasket, Link, Governor Weight Assy, Sleeve, Control Shaft Assy, Shaft Spacer |
| Governor | 28-29 | Stop Motor Assy, Stop Motor Spring, Snap Ring, Stop Motor Bracket |
| Engine Stop | 30-31 | Starter, Cover, Retainer, Clutch Kit, Pinion, Shaft, Ring, Coil Spring |
| Starting Motor | 32-33 | Generator, Rotor Assy, Bearing Cover, Drive Flame Assy, Plate, Rear Flame Assy, Cover, Crankshaft Pulley |
| Generator | 34-35 | Flex Horn, Gasket Set, Cylinder Head Gasket, Hydraulic Oil Pump Gasket, Bonnet Gasket, Valve Stem Seal, Nozzle Protector, Nozzle Seat |
| Tool & Gasket Set | 36-37 | Gasket, Cyl. Head, Suc. Manifold, Exh. Manifold, O-Ring, F.I. Pump |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Main Bearing Oversize | 0.25U.S | p. 2 |
| Crankpin Bearing Oversize | 0.25U.S | p. 14 |
| Piston w/Ring Oversize | 0.25 | p. 14 |
| Ring Set Oversize | 0.25 | p. 14 |
| V-Belt Type/Size | A-39 | p. 18 |
| Link Length (Mark 0) | 30 | p. 26 |
| Link Length (Mark 1) | 31 | p. 26 |
| Link Length (Mark 05) | 30.5 | p. 26 |
Yanmar 3TNC78L-RKAH (V2), 3TNC78L-RKAH Common Problems This Manual Covers
Hard starting from injection pump wear
When plungers and delivery valves wear, injection pressure bleeds off and the engine cranks without firing. The catalog breaks the pump down to the plunger with barrel, delivery valve with seat, and tappet assembly, so you can replace the worn internals by part number instead of buying a complete pump.
Manual Section: Fuel Injection Pump p. 21Smoke and misfire from tired injectors
Worn nozzles dribble instead of atomizing, showing up as white or black smoke, uneven running, and diesel knock. The injector breakdown lists the nozzle assembly, holder assembly, and springs separately, so a rebuild costs a fraction of three new injectors.
Manual Section: Fuel Injection Device p. 23Surging or hunting under load
An engine that hunts at steady load usually has wear in the governor linkage or weight assembly. This section shows the governor case, weight assembly, link, control shaft, and lever assembly with part numbers for each.
Manual Section: Governor p. 28Engine will not shut off
A failed stop motor or broken return spring leaves the engine running with the key off. The catalog covers the stop motor assembly, spring, snap ring, and mounting bracket so you can identify exactly which piece gave up.
Manual Section: Engine Stop p. 30Low oil pressure warnings
A flickering oil light can be a lazy pressure switch, a clogged strainer, or a worn oil pump. This section lays out the lube oil pump, strainer, inlet pipe, filter, and pressure switch so you can chase the cheap causes before condemning bearings.
Manual Section: Lub. Oil System p. 17Overheating and coolant loss
A slipping V-belt, stuck thermostat, or leaking water pump seal will cook a small diesel quickly. The cooling breakdown covers the pump assembly, thermostat, fan, gaskets, and the A-39 V-belt by part number.
Manual Section: Cooling Water System p. 19Rebuilding a worn bottom end
If crank journals or bores are past standard, this section lists 0.25 oversize crankpin bearings, pistons with rings, and ring sets alongside the crankshaft, connecting rod, and piston pin bush, so you can spec the whole rotating assembly before the machine shop call.
Manual Section: Crankshaft & Piston p. 15Frequently Asked Questions
Which engine does this parts catalog cover?
It covers the Yanmar 3TNC78L-RKAH (V2) diesel engine, Yanmar publication Y00B4192, 37 pages in English, running from the Cylinder Block section through the Generator and a Tool & Gasket Set listing. It is specific down to the variant marks: the governor link is listed by mark on page 26, 30 mm for mark 0, 30.5 mm for mark 05 and 31 mm for mark 1.
Does it list oversize parts for a rebuild?
Yes. The Crankshaft & Piston section lists 0.25 oversize crankpin bearings, pistons with rings, and ring sets, and the Cylinder Block section lists 0.25 oversize main bearings, so you can order rebuild parts to match your machined clearances. p. 15
Are gaskets and seals covered?
Yes. The Tool & Gasket Set section lists the cylinder head gasket, suction and exhaust manifold gaskets, and the fuel injection pump O-ring, and individual oil seals and O-rings appear throughout the housing and sump sections. p. 36
Is this a service manual with torque specs and procedures?
No. This is a parts catalog: exploded views with Yanmar part numbers for every assembly, from the Fuel Injection Pump to the Starting Motor. Use it to identify and order parts; it does not contain step-by-step repair procedures.
What exactly do I receive with this Yanmar 3TNC78L-RKAH (V2) Parts Catalog?
Instant PDF download. You get the full 37-page searchable Parts Catalog immediately after payment. Open it on your laptop, tablet, or phone right in the shop.
Can I print a copy of this Yanmar 3TNC78L-RKAH (V2) Parts Catalog for the shop?
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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