All 693 pages of this Cummins Big Cam III, Big Cam IV, NT 855 repair manual PDF (OEM #3810298-00) exist for one job: putting your Big Cam or NT 855 diesel engine back to factory spec. You get a full troubleshooting section with symptom, cause, and correction charts, plus flow diagrams for the cooling, lube, combustion air, and fuel systems. Inside: fuel pump adjustment, injector replacement, crosshead and valve setting, Jacobs brake adjustment, and a complete torque section covering capscrew markings and pipe plug values. Check fuel filter restriction against the factory numbers: 100 mm Hg (4.0 in Hg) clean, 200 mm Hg (8.0 in Hg) means swap it. A Big Cam won't forgive guesswork. Bookmarked PDF opens on laptop, tablet, or phone; tap a section and carry it straight to the engine bay.
What's Inside This Cummins Big Cam III, Big Cam IV, NT 855 Repair Manual
| System | Pages | Key Topics |
|---|---|---|
| Introduction | 4-13 | About the Manual, How to Use the Manual, Symbols, Illustrations, Definition of Terms, General Repair Instructions, General Cleaning Instructions |
| Engine Identification | 14-19 | Engine Specifications, Engine Diagrams |
| Troubleshooting | 20-93 | Procedures and Techniques, Symptoms List, Symptoms Cause and Corrections Charts |
| Cooling System | 94-185 | Service Tools, General Information, Specifications, Flow Charts, Venting, Maintenance |
| Lubricating Oil System | 186-235 | Service Tools, General Information, Demand Flow and Cooling Lubricating System - Operation, Specifications, Flow Diagrams, Internal Engine Damage - Check |
| Combustion Air System | 236-271 | General Information, Specifications, Flow Diagrams, Service Tools, Turbocharger Turbine Seal Leaks Check, Compressor Seal Leakage - Check, Correct Turbocharger Installed - Check |
| Compressed Air System | 272-295 | General Information, Specifications, Flow Diagrams, Service Tools, Carbon Buildup, Air Compressor Check, Gasket Leaks, Air Compressor - Check |
| Fuel System | 296-382 | General Information, Specifications, Flow Diagrams, Service Tools, Fuel Pump Adjust, Injectors - Replace, Fuel Pump - Replace, Fuel System Maintenance |
| Electrical System | 383-399 | General Information, Specifications, Service Tools, Batteries - Check, Battery Terminal Connections - Check, Starting Circuit - Check, Alternator Belt - Adjust |
| Base Engine Components | 400-634 | Service Tools, General Information, Rocker Housing Covers - Replace, Engine Lifting Brackets - Replace, Crossheads, Valves and Injectors Adjust, Jacobs Engine Brake - Adjust |
| Engine Testing ("in Chassis") | 635-646 | Service Tools, General Engine Test Specifications and Procedures, Chassis Dynamometer Operation, Engine Run-In Procedure (Chassis Dynamometer) |
| Engine Remove and Install | 647-653 | General Information, Service Tools, Engine Remove, Engine Mounts - Inspect, Engine - Install |
| Engine Component Specifications | 654-678 | General Information, Conversion Factors, Pipe Plug Torque Values, Capscrew Markings and Torque Values, Decimal and Metric Equivalents, Cooling System Torque Values |
| Additional Service Literature | 687-689 | Compuchek Operation Manual, Service Tools Catalog, Fuel for Cummins Engines, Injectors Pt Rebuild Manual, Nt Engine Shop Manual, Turbochargers Rebuild Manual |
| Accessory Component Manufacturers | 690-693 | Air Cylinders, Alternators, Belts, Clutches, Fans, Governors |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Troubleshooting and Repair Manual | Big Cam III and Big Cam IV, NT 855 Engines | p. 1 |
| Dipstick calibration correction | approximately 38 mm [1.5 inches] | p. 203 |
| Clean Fuel Filter | 100 mm Hg. (4.0 inch Hg.) | p. 298 |
| Dirty Fuel Filter | 200 mm Hg. (8.0 inch Hg.) | p. 298 |
| Fuel Drain Line Maximum Restriction Without Check Valves | 65 mm Hg. (2.5 inch Hg.) | p. 298 |
| Fuel Drain Line Maximum Restriction With Check Valves | 165 mm Hg. (6.5 inch Hg.) | p. 298 |
| Engine Displacement | 14.0 liters [855 cu. in.] | p. 16 |
| Total System Oil Capacity (including filters) | 42 liters [11.0 U.S. gal.] | p. 16 |
| Coolant Capacity (engine only) | 21 liters [22 U.S. quarts] | p. 17 |
| Maximum Coolant Cylinder Block Pressure (pressure cap removed) | 350 kPa [50 psi] | p. 17 |
| Maximum Allowable Exhaust Back Pressure | 1000 mm H20 [40 in. H20] | p. 17 |
| Fuel Inlet Maximum Restriction (Clean Fuel Filter) | 100 mm Hg [4 in. Hg] | p. 17 |
Cummins Big Cam III, Big Cam IV, NT 855 Common Problems This Manual Covers
Cummins Big Cam III low power under load, won't reach rated RPM, black smoke on grades
Check fuel inlet restriction with a vacuum gauge at the pump inlet. Replace the fuel filter if restriction exceeds 100 mm Hg (4 in. Hg) with a clean filter, the limit shown on page 361. Inspect the suction line for kinks and pull the tank stand pipe to check for cracks letting air in.
Manual Section: Fuel System p. 361Engine starts then stalls, hard to restart, air bubbles visible in the fuel supply line
Tighten every suction-side fitting from tank to pump and inspect the filter seal for nicks. Measure drain line restriction; it must stay under 65 mm Hg (2.5 in. Hg) without check valves, per the specs on page 298. Pull the tank stand pipe and check for cracks above the fuel level, then bleed the system and retest.
Manual Section: Fuel System p. 298Engine surges at idle, hunts under light load, idle speed will not hold steady
Verify idle speed first; adjust the fuel pump idle screw until the engine holds 650 to 725 RPM, the spec on page 298. Chase air ingress before touching anything else: tighten suction fittings and inspect the filter seal, since air makes any idle adjustment useless. Confirm the throttle linkage returns fully against its stop.
Manual Section: Fuel System p. 298Oil level reads low right after a full service fill, gauge pressure drops on grades
Verify total system oil capacity of 42 liters (11.0 U.S. gallons) including filters, listed on page 16. If a blank replacement dipstick was installed, calibrate it: cut it off approximately 38 mm (1.5 inches) below the LOW mark, per the procedure on page 203. Refill to the corrected mark and recheck pressure at operating temperature.
Manual Section: Lubricating Oil System p. 203Coolant temperature climbs above normal on long pulls, overflow bottle pushes coolant out
Check coolant level cold against the engine-only capacity of 21 liters (22 U.S. quarts) on page 17. Pressure-test the cap and inspect the radiator core for external plugging. After any refill, vent the system using the procedure in the cooling section beginning on page 94, since trapped air mimics a bad thermostat. Retest under load.
Manual Section: Cooling System p. 94Frequently Asked Questions
How to reset Cummins Big Cam III injector timing after camshaft replacement?
After camshaft replacement, the injector timing for a Cummins Big Cam III engine needs to be adjusted. This involves measuring the injector push rod travel in relation to the piston travel and can be changed by increasing or decreasing the cam follower gasket thickness. Each 0.18 mm [0.007-inch] change in gasket thickness affects injection timing by approximately 0.05 mm [0.002-inch] indicator travel. For detailed instructions, refer to Procedure 7-17. p. 492
What are the torque specs for Cummins NT 855 Big Cam III rocker arm bolts?
The torque specifications for rocker arm bolts on a Cummins NT 855 Big Cam III engine vary depending on the component. For rocker lever cover mounting capscrews, the torque is 20 N•m [15 ft-lbs]. For rocker lever housing mounting capscrews, the torque is 80 N•m [60 ft-lbs]. p. 671
How to reset Cummins NT 855 STC (Step Timing Control) system?
The manual refers to the Mechanical Variable Timing (MVT) system, not STC. To adjust the MVT system timing, first remove the electrical wire at the MVT air solenoid valve and operate the engine at low idle for at least 30 seconds to put the actuator in retarded mode. Then, install Part No. 3375522 Injection Timing Tool in cylinder No. 3 and rotate the MVT spring retainer clockwise until the indicator needle stops moving counterclockwise, setting the maximum retarded timing position. Refer to Procedure 7-18 for full details. p. 501
What are the torque specs for Cummins Big Cam IV fuel injector retaining bolt?
For the Cummins Big Cam IV engine, the fuel injector retaining bolts are referred to as injector hold down clamp capscrews. These capscrews should be tightened alternately and evenly to a final torque of 16 to 19 N•m [144 to 168 in-lb]. The general torque specification for injector hold down clamps is 18 N•m [156 in-lbs]. p. 671
How to reset Cummins Big Cam IV STC system timing?
To adjust the Mechanical Variable Timing (MVT) system timing on a Cummins Big Cam IV engine, begin by removing the electrical wire from the MVT air solenoid valve and running the engine at low idle for 30 seconds to engage retarded mode. Then, install the Part No. 3375522 Injection Timing Tool in cylinder No. 3, as described in Procedure 7-17. Rotate the MVT spring retainer clockwise until the indicator needle stops moving counterclockwise, which sets the maximum retarded timing position. This procedure ensures the timing is correctly set for optimal engine performance. p. 501
What format is this Cummins Big Cam III, Big Cam IV, NT 855 manual in?
This is a 693-page scanned PDF ready for immediate download. Works on any device, so pull it up on your phone while you're under the hood. No shipping, no waiting.
Is this Cummins Big Cam III, Big Cam IV, NT 855 Repair Manual printable?
Yes. The PDF has no DRM restrictions, so print any page or section you need for your shop. Works with any standard printer.
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