John Deere 6068TF250 Specifications
| Engine Model: John Deere PowerTech 6068TF250 |
| Engine Type: 4-stroke in-line 6-cylinder turbocharged liquid-cooled diesel |
| Total Displacement: 415 cu.in (6.8 L) |
| Rated Engine Power: 173 Hp (129 kW) at 2500 rpm |
| Fuel System Type: Direct Injection |
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The John Deere 6068TF250 is a 6.8-liter,
6-cylinder PowerTech diesel engine engineered for heavy-duty industrial
and generator set applications. This power unit operates within Tier 2
(Stage II) emission standards, utilizing a mechanical fuel system
without electronic controls. The TF250 designation indicates a
turbocharged, liquid-cooled configuration with a Stanadyne DB4 rotary
distributor pump. This engine is recognized for its high torque rise
characteristic, reaching 30%, which allows operation under variable
loads without frequent gear changes.
The wet-sleeve cylinder liner design simplifies overhauls, while the
forged-steel crankshaft and high-strength cast iron block provide
structural integrity for continuous operation in construction equipment,
irrigation pumps, and prime power generators. This model preceded the
electronic PowerTech Plus series, offering a mechanical alternative for
operators requiring field serviceability without diagnostic computers.
Engine Type: In-line, 4-cycle diesel, turbocharged, liquid-cooled
Number of Cylinders: 6
Displacement: 6.8 L (415 cu.in)
Bore x Stroke: 106 mm x 127 mm (4.17 in x 5.00 in)
Compression Ratio: 17.0:1
Firing Order: 1-5-3-6-2-4
Rotation (from flywheel end): Counter-clockwise
Rated Power (Industrial): 173 hp (129 kW) at 2500 rpm
Rated Power (Generator 60 Hz): 166 hp (124 kW) at 1800 rpm
Rated Power (Generator 50 Hz): 139 hp (104 kW) at 1500 rpm
Peak Torque: 643 Nm (474 lb-ft) at 1400 rpm
Torque Rise: 30%
Low Idle Speed: 800-900 rpm (industrial) / 750 rpm (generator)
High Idle Speed (no-load): 2700 rpm (industrial)
High Idle Speed (no-load): 1875 rpm (60 Hz generator)
High Idle Speed (no-load): 1575 rpm (50 Hz generator)
Aspiration: Turbocharged (fixed geometry)
Emission Standard: EPA Tier 2 / EU Stage II
The cylinder block is constructed from high-tensile cast iron with a
deep-skirt design extending below the crankshaft centerline. This
configuration enhances rigidity and reduces noise emission. The block
incorporates replaceable wet-sleeve cylinder liners, each sealed at the
lower bore by two O-rings and at the upper flange by a pressed-in fire
ring. Liners are made from centrifugally cast alloy iron with a hardened
internal bore surface.
The block features seven main bearing bulkheads with cross-bolted main
bearing caps on the center three positions for added strength. The water
jacket surrounds each liner fully, permitting direct coolant contact for
efficient heat removal. Cast oil galleries run the full length of the
block, supplying pressurized lubricant to the main bearings and piston
cooling jets.
The cylinder head is a single-piece cast iron component with a
cross-flow design. The intake manifold mounts on the right side, while
the exhaust manifold mounts on the left side when viewed from the
flywheel end. Each cylinder receives two valves: one intake and one
exhaust, arranged in a parallel valve layout. The valvetrain is an
overhead valve (OHV) configuration with pushrods and rocker arms.
Valve stem seals are positive-type on both intake and exhaust valves.
Hardened valve seat inserts resist wear under elevated exhaust
temperatures. The cylinder head incorporates a pre-combustion chamber
design in certain generator configurations, though the TF250 industrial
variant uses direct injection with bowl-in-piston combustion. Valve
rotators on exhaust valves extend service life by preventing localized
hot spots.
The fuel system is a mechanical direct injection design without
electronic control. A Stanadyne DB4 series rotary distributor pump
serves as the injection pump. This pump uses a hydraulic head with four
pumping plungers arranged radially. Fuel enters the pump through a
vane-type transfer pump, which raises pressure to 4-6 bar (58-87 psi)
before the plungers compress fuel to injection pressure of 350-400 bar
(5075-5800 psi).
A mechanical centrifugal governor, integrated into the pump housing,
modulates fuel delivery to maintain set engine speed under varying
loads. The governor includes both spring-loaded idle and maximum speed
control mechanisms. Injection lines are equal length, routed
individually to each injector nozzle. Multi-hole injector nozzles
(5-hole) have an opening pressure of 220 bar (3190 psi). A manual primer
pump on the injection pump facilitates bleeding air from the system
after filter changes.
The lubrication system is a full-flow pressurized design utilizing a
gear-type pump mounted on the front timing gear case. The pump draws oil
through a suction strainer positioned in the lower sump. Oil passes
through a spin-on full-flow filter with a bypass valve set at 2.1 bar
(30 psi). The system incorporates piston cooling: six oil jets, one per
cylinder, are threaded into the main oil gallery.
Each jet directs a continuous stream toward the underside of the piston
crown. A water-cooled oil cooler, mounted on the right side of the
block, uses engine coolant to regulate oil temperature. The oil pressure
relief valve opens at 5.5 bar (80 psi). Oil capacity including filter is
19.0 L (20.0 qt). Oil pressure at rated speed measures 3.4-4.8 bar
(50-70 psi). Low oil pressure shutdown is not standard; a pressure
switch activates a warning lamp.
The cooling system is a pressurized, liquid-cooled design with a
centrifugal water pump driven by the crankshaft via a poly-ribbed belt.
Coolant circulates from the radiator bottom tank into the block, flows
upward around the wet-sleeve liners, passes through the cylinder head,
then exits through the thermostat housing to the radiator top tank. A
wax-pellet thermostat begins opening at 82°C (180°F) and achieves full
opening at 95°C (203°F).
A bypass circuit permits coolant circulation within the engine during
thermostat closure for rapid warm-up. Coolant capacity for the engine
alone is 11.3 L (11.9 qt). Total system capacity, including radiator and
hoses, ranges from 25.0 to 35.0 L (26.4-37.0 qt) depending on
installation. Coolant specification requires heavy-duty diesel
antifreeze with supplemental coolant additives (SCA).
Aspiration: Fixed-geometry turbocharger manufactured by Holset or
BorgWarner. The turbocharger uses a single journal bearing and a
wastegate valve to limit maximum boost pressure to 1.2 bar (17.4 psi) at
rated speed.
Exhaust System: Single log-style exhaust manifold constructed from
nodular cast iron. The manifold incorporates a turbocharger mounting
flange on the front or center position, depending on configuration.
Electrical System: 12 volt or 24 volt negative ground, specified at
order. Starter motor rating is 4.0 kW (12V) or 5.5 kW (24V). Alternator
output ranges from 55 A to 120 A.
Governor: Mechanical centrifugal governor integral to the injection
pump. Governor response includes both droop and isochronous settings
selectable by spring configuration.
Length (flywheel housing to fan hub): 1220 mm (48.0 in)
Width (overall, exhaust manifold to fuel pump): 640 mm (25.2 in)
Height (oil pan rail to rocker cover): 905 mm (35.6 in)
Dry Engine Weight (without flywheel, starter, alternator): 590 kg (1300
lb)
Dry Weight (fully dressed, industrial version): 680 kg (1500 lb)
Engine Oil Change Interval: 500 hours under normal operating conditions.
Engine Oil Capacity (including filter): 19.0 L (20.0 qt).
Engine Oil Grade (ambient above -10°C / 14°F): SAE 15W-40, API CI-4 or
higher.
Engine Oil Grade (cold ambient): SAE 10W-30, API CI-4 or higher.
Engine Oil Pressure at Rated Speed: 3.4-4.8 bar (50-70 psi)
Engine Oil Pressure at Low Idle (min): 0.7 bar (10 psi) at operating
temperature.
Coolant Capacity (engine only): 11.3 L (11.9 qt).
Coolant Capacity (system total): 25.0-35.0 L (26.4-37.0 qt).
Coolant Specification: Ethylene glycol base, heavy-duty formulation.
Coolant SCA Concentration: 2.0-3.0 units per liter (8-12 units per
gallon).
Thermostat Opening Temperature: 82°C (180°F) primary; 88°C (190°F)
optional.
Fuel Filter Replacement Interval: 500 hours. Primary and secondary
spin-on filters.
Air Filter Service Interval: Replace when restriction indicator reaches
6.2 kPa or annually.
Intake Valve Clearance (Cold, Mechanical Lifters): 0.36 mm (0.014 in).
Exhaust Valve Clearance (Cold, Mechanical Lifters): 0.46 mm (0.018 in).
Valve Clearance Inspection interval: 1000 hours.
Injection Pump Timing: 14.0 degrees before top dead center at No. 1
cylinder.
Injector Nozzle Opening Pressure: 220 bar (3190 psi). Replacement
interval 2000 hours.
Turbocharger Inspection Interval: 1500 hours. Check for shaft end play
and radial play.
Drive Belt Tension: Automatic spring tensioner. Replace belt every 1000
hours.
Cylinder Liner Protrusion: 0.05-0.13 mm (0.002-0.005 in) above block
deck.
Valve Recession (intake/exhaust): 0.75-1.20 mm (0.030-0.047 in) below
cylinder head face.
Cylinder Head Bolts (Stage 1): 100 Nm (75 lb-ft)
Cylinder Head Bolts (Stage 2): 150 Nm (110 lb-ft)
Connecting Rod Cap Bolts: 58 Nm (43 lb-ft)
Main Bearing Cap Bolts (center three caps, inner): 135 Nm (100 lb-ft)
Main Bearing Cap Bolts (end caps, inner): 135 Nm (100 lb-ft)
Main Bearing Cap Cross Bolts (center three caps): 80 Nm (59 lb-ft)
Flywheel Bolts (to crankshaft flange): 130 Nm (95 lb-ft)
Flywheel Housing Bolts (to block): 90 Nm (66 lb-ft)
Camshaft Thrust Plate Bolts: 30 Nm (22 lb-ft)
Rocker Arm Shaft Pedestal Bolts: 45 Nm (33 lb-ft)
Rocker Cover Nuts: 12 Nm (9 lb-ft)
Injection Pump Drive Gear Nut: 120 Nm (89 lb-ft)
Injection Line Fittings (pump and nozzle): 35 Nm (26 lb-ft)
Injector Hold-Down Clamp Bolt: 25 Nm (18 lb-ft)
Crankshaft Pulley Bolts: 90 Nm (66 lb-ft)
Viscous Damper Bolt (center): 450 Nm (332 lb-ft)
Oil Pan Bolts (M10): 35 Nm (26 lb-ft)
Oil Pan Drain Plug: 50 Nm (37 lb-ft)
Oil Filter Mount (spin-on canister): 25 Nm (18 lb-ft)
Water Pump Mounting Bolts: 40 Nm (30 lb-ft)
Thermostat Housing Bolts: 25 Nm (18 lb-ft)
Starter Motor Mounting Bolts: 65 Nm (48 lb-ft)
Alternator Bracket Bolts: 45 Nm (33 lb-ft)
Turbocharger Mounting Nuts (to manifold): 60 Nm (44 lb-ft)
Turbocharger Oil Supply Line Fitting: 25 Nm (18 lb-ft)
Agricultural Tractors: John Deere 6105D, 6115D (Tier 2/Stage II
configurations). Also found in 7810, 7910, and 8100 series row-crop
tractors as a replacement engine.
Construction Equipment: John Deere 310SG, 315SG backhoe loaders. JD
544K, 624K wheel loaders. JD 200C, 270C excavators. JD 550J, 650J dozers
with 6.8L PowerTech engines.
Generator Sets: John Deere 6068TF250 generator drive for prime power at
1500 rpm (50 Hz) or 1800 rpm (60 Hz). Used in DE17 and DE25 series
generator enclosures. Standby power rating 145-155 kVA.
Industrial Power Units: Irrigation pump drives (center pivot systems).
Hydraulic power packs for oilfield equipment. Wood chippers and
horizontal grinders.
Marine (Limited): Auxiliary power generators on vessels. Small
commercial workboat propulsion (reduced rating to 150 hp continuous).
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