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Cummins 4BTAA3.9 Engine

The Cummins 4BTAA3.9 is a 3.9-liter, four-cylinder, inline, turbocharged, and charge-air-cooled diesel engine widely used in automotive, industrial, and power generation applications. Engine design features a deep-skirt block without cylinders liners (parent-bore design), which maximizes structural rigidity. A forged steel crankshaft and high-strength connecting rods provide excellent resistance to thermal and mechanical fatigue. Because it relies primarily on mechanical controls rather than complex electronics, this powerplant is favored globally for its ease of maintenance, reliability in harsh environments, and high rebuildability.

Fuel injection uses a fully mechanical system featuring either a Bosch VE rotary distribution pump or a Bosch P7100 inline injection pump. Timing control is strictly mechanical and driven directly via the engine gear train. Fuel delivery relies on a mechanical lift pump to supply the injection pump with low-pressure fuel. Filtration relies on a spin-on fuel filter and water separator unit installed on the suction side. Injectors are multi-hole, direct-injection nozzles that spray fuel directly into the toroidal piston bowls.

Lubrication system uses a full-pressure, gear-driven oil pump that circulates oil through internal drillings. Filtration utilizes a single spin-on combination full-flow and bypass filter element. An integrated plate-type oil cooler regulates oil temperature using engine coolant.

Cooling system utilizes a liquid-cooled design with forced circulation via an integrated, belt-driven centrifugal water pump. Temperature regulation relies on a pellet-type thermostat that opens at 82C (180F) and fully opens at 95C (203F). Air-to-air charge cooling lowers the temperature of intake air post-turbocharger to optimize combustion efficiency.

General Technical Data

Engine Specifications

Engine Model ............... Cummins 4BTAA3.9
Engine Type ............... 4-cycle inline 4-cylinder direct injection turbocharged liquid-cooled diesel
Number of Cylinders ............... 4
Cylinder Arrangement ............... In-line
Engine Bore, in (mm) ............... 4.02 (102.0)
Engine Stroke, in (mm) ............... 4.72 (120.0)
Displacement, cu.in (L) ............... 239 (3.9)
Rated Engine Power, hp (kW) ............... 80-130 (60-97)
Rated Engine Speed, rpm ............... 2400-2800
Peak Torque ............... 350-500 Nm (260-370 lb-ft) at 1300-1600 rpm
Idle Speed ............... 750-850 rpm
Aspiration Type ............... Turbocharged and aftercooled
Compression Ratio ............... 16.5:1-17.5:1
Firing Order ............... 1-3-4-2
Cylinder Block Type ............... Cast iron
Cylinder Head Type ............... Cast iron
Lubrication System ............... Full-pressure
Oil Pump Type ............... Gear-driven
Oil Filter Type ............... Full-flow, spin-on
Cooling System ............... Liquid-cooled
Water Pump Type ............... Belt-driven, centrifugal
Air Cleaner Type ............... Dry dual-stage
Starting System ............... Electric Starter
Electrical System ............... 12V or 24V
Alternator Rating, Amps ............... 35-75

Fuel System

Fuel System ............... Direct injection
Injection Pump Type ............... Rotary
Fuel System Control ............... Mechanical
Governor Type ............... Mechanical
Fuel Injector Type ............... Multi-hole
Fuel Type ............... Diesel Fuel

Dimensions and Weight

Overall Length, in (mm) ............... 33.5-37.4 (850-950)
Overall Width, in (mm) ............... 25.6-31.5 (650-800)
Overall Height, in (mm) ............... 35.4-39.4 (900-1000)
Dry Weight, lbs (kg) ............... 730-840 (330-380)

Maintenance Data

Service Information

Thermostat begins opening ............... 82C (180F)
Thermostat fully open ............... 95C (203F)
Cooling system pressure ............... 70-100 kPa (10-15 psi)
Operating oil pressure ............... 300-450 kPa (44-65 psi)
Idle oil pressure ............... 100-150 kPa (15-22 psi)
Intake Valve Clearance, in (mm) ............... 0.254 (0.010)
Exhaust Valve Clearance, in (mm) ............... 0.508 (0.020)

Engine Oil and Coolant

Engine Oil Type .................. SAE 10W-30, 15W-40
API Service Classifications ......................... CF or higher
Engine Oil Capacity, qts (L) .................. 9.5-12.6 (9.0-12.0)
Coolant Capacity, qts (L) ............... 12.6-16.8 (12.0-16.0)

Service Intervals

Change oil and filter ............... Every 250 hours
Replace fuel filters ............... Every 300 hours
Inspect air filter ............... Every 100 hours
Replace air filter ............... Every 300 hours
Change coolant ............... Every 2000 hours
Valve-lash adjustment ............... Every 1000 hours
Injector inspection ............... Every 1500-2000 hours
Compression test ............... Every 3000 hours
Drain water separator ............... As required
Belt inspection ............... As required

Service Specifications

Cylinder Bore Inside Diameter, in (mm) ............... 4.0161-4.0177 (102.000-102.040)
Crankshaft Journal Outside Diameter, in (mm) ............... 3.2661-3.2681 (82.960-83.010)
Crank Pin Outside Diameter, in (mm) ............... 2.7150-2.7169 (68.960-69.010)
Crankshaft End Play, in (mm) ............... 0.0040-0.0170 (0.102-0.432)
Intake Valve Stem Outside Diameter, in (mm) ............... 0.3134-0.3142 (7.960-7.980)
Exhaust Valve Stem Outside Diameter, in (mm) ............... 0.3126-0.3134 (7.940-7.960)
Intake Valve Guide Inside Diameter (Installed), in (mm) ............... 0.3157-0.3169 (8.020-8.050)
Exhaust Valve Guide Inside Diameter (Installed), in (mm) ............... 0.3157-0.3169 (8.020-8.050)
Intake Valve Stem to Guide Clearance, in (mm) ............... 0.0015-0.0036 (0.038-0.091)
Exhaust Valve Stem to Guide Clearance, in (mm) ............... 0.0025-0.0046 (0.064-0.117)
Intake Valve Spring Free Length, in (mm) ............... 2.150 (54.61)
Exhaust Valve Spring Free Length, in (mm) ............... 2.150 (54.61)
Intake Cam Height, in (mm) ............... 1.831 (46.51)
Exhaust Cam Height, in (mm) ............... 1.819 (46.20)
Piston Pin Outside Diameter, in (mm) ............... 1.5744-1.5752 (39.990-40.010)
Piston Pin to Piston Bore Clearance, in (mm) ............... 0.0002-0.0007 (0.005-0.018)
Second Ring Side Clearance, in (mm) ............... 0.0028-0.0045 (0.070-0.115)
Oil Ring Side Clearance, in (mm) ............... 0.0020-0.0035 (0.050-0.090)
Top Ring End Gap, in (mm) ............... 0.0100-0.0220 (0.250-0.550)
Second Ring End Gap, in (mm) ............... 0.0100-0.0220 (0.250-0.550)
Oil Ring End Gap, in (mm) ............... 0.0100-0.0220 (0.250-0.550)

Tightening Torque Specs

Cylinder head bolts ............... 160-180 Nm (118-133 lb-ft)
Main bearing caps ............... 150-170 Nm (111-125 lb-ft)
Connecting rod bolts ............... 70-85 Nm (52-63 lb-ft)
Flywheel bolts ............... 180-220 Nm (133-162 lb-ft)
Crankshaft pulley bolt ............... 200-240 Nm (148-177 lb-ft)
Glow plugs ............... 10-15 Nm (7-11 lb-ft)
Oil drain plug ............... 30-40 Nm (22-30 lb-ft)
Injector hold-down bolts ............... 20-25 Nm (15-18 lb-ft)

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• Cummins Engines Specs
  
• Cummins 4B3.9-G2 Specs
  
• Cummins 4B3.9-G11 Specs
  
• Cummins 4BT3.9-G2 Specs
  
• Cummins 4BTA3.9-G2 Specs
  
• Cummins 4BTA3.9-G11 Specs
  
• Cummins 4BTAA3.3-G11 Specs
  

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