With fuel filters coming off your engine this afternoon, the 342-page Cummins QSB4.5, QSB6.7 Operation and Maintenance Manual PDF (OEM number 4021531) is the factory book written for both engines. Maintenance intervals run from the daily checks through the 250, 500, 1000, and 2000 hour services out to the 5000 hour or four year mark, and that schedule fills a large share of the book. Flow diagrams trace the fuel, lubricating oil, and cooling circuits, while the troubleshooting symptom charts let you match a complaint to its probable cause and the next check to make. Let coolant fall below 50°C [122°F] before you loosen the pressure cap, and torque the fuel filter to 34 N·m [25 ft-lb]. A parked engine waiting on one number costs a day. Buy it once and this bookmarked, text-searchable copy stays yours for every service interval these engines will ever see.
What's Inside This Cummins QSB4.5, QSB6.7 Operator Manual
| System | Pages | Key Topics |
|---|---|---|
| Introduction | 7-22 | About the Manual, General Safety Instructions, General Cleaning Instructions |
| Engine Identification | 23-38 | Engine Dataplate, Engine Diagrams |
| Industrial Features | 39-50 | Fan Control, Idle Shutdown, Accelerator Options |
| Operating Instructions | 51-62 | Normal Starting Procedure, Operating the Engine, Electromagnetic Interference |
| Maintenance Guidelines | 63-118 | Maintenance Procedures at Daily Interval, Maintenance Procedures at 250 Hours or 3 Months, Maintenance Procedures at 500 Hours or 6 Months |
| Adjustment, Repair, and Replacement | 119-142 | Alternator, Charge-Air Cooler, Coolant Thermostat |
| System Diagrams | 143-162 | Flow Diagram, Fuel System, Lubricating Oil System, Cooling System |
| Service Literature | 163-168 | Additional Service Literature, Service Literature Ordering Location, Cummins Customized Parts Catalog |
| Component Manufacturers | 169-174 | Component Manufacturers Addresses |
| Service Assistance | 175-236 | Division and Regional Offices, Distributors and Branches, Distributors International |
| Troubleshooting Symptoms | 237-302 | Troubleshooting Procedures and Techniques, Troubleshooting Symptoms Charts |
| Maintenance Specifications | 303-324 | General Engine, Fuel System, Lubricating Oil System |
| Warranty | 325-342 | All Engines United States and Canada Industrial, All Engines International Industrial, California Emission Control System Warranty |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| Air Compressor Mounting Torque | 77 N·m [57 ft-lb] | p. 78 |
| Air Compressor Bracket Torque | 45 N·m [33 ft-lb] | p. 78 |
| Fuel filter torque | 34 N·m [25 ft-lb] | p. 90 |
| Coolant temperature for safe removal of pressure cap | below 50°C [122°F] | p. 103 |
| Thermostat Initial Opening Temperature (Automotive) | 81 °C [178 °F] | p. 133 |
| Thermostat Fully Opened Temperature (Automotive) | 94 °C [202 °F] | p. 133 |
| Starting Motor Spacing (MIN) | 49.28 mm [1.94 in] | p. 141 |
| Starting Motor Spacing (MAX) | 52.32 mm [2.06 in] | p. 141 |
| Minimum Recommended Pressure Cap | 50 kPa [7 psi] | p. 308 |
| Valve Clearance Intake | 0.254 mm | p. 305 |
| Valve Clearance Exhaust | 0.508 mm | p. 305 |
| Coolant Capacity | 8.5 liters | p. 308 |
Cummins QSB4.5, QSB6.7 Common Problems This Manual Covers
Cummins QSB4.5 or QSB6.7 engine coolant temperature climbing above normal once the engine is warm
Check the coolant level only after temperature falls below 50°C [122°F], since page 103 warns against removing the pressure cap any hotter. Verify the cap is rated at least 50 kPa [7 psi] and the thermostat matches the standard modulating range of 88 to 97°C [190 to 207°F] on page 308.
Manual Section: Coolant p. 308Lubricating oil pressure reading lower than normal at low idle and at rated speed
Check the oil level first, then compare gauge readings against the page 307 values of 103 kPa at low idle and 310 kPa at rated speed. If pressure falls short with the level correct, shut the engine down and work through the Lubricating Oil pressure low chart before running it again.
Manual Section: Lubricating Oil p. 307Excessive black smoke from the exhaust and engine power output noticeably low
Measure intake restriction at the air filter. Page 309 lists 254 mm H2O maximum with a clean element and 635 mm H2O with a dirty one; replace the element once it reaches that dirty limit. Then check exhaust back pressure against 10 kPa without an exhaust catalyst or 15 kPa with one, per page 310.
Manual Section: Smoke p. 309Engine difficult to start, and when it fires it will not keep running
Measure fuel inlet restriction and compare it to the 50.7 kPa maximum on page 306; verify fuel inlet temperature stays below 70°C. If restriction runs high, replace the fuel filter following the procedure on page 90, then recheck before cranking again.
Manual Section: Engine Performance p. 306Alternator not charging or showing insufficient charging output while the engine is running at speed
Check the Alternator symptom chart first, since it separates not charging, insufficient charging, and overcharging into their own steps. Inspect the alternator using the procedure in Adjustment, Repair, and Replacement starting on page 119 before you condemn the unit and order a replacement.
Manual Section: AlternatorFrequently Asked Questions
What are the fuel filter replacement specifications for the Cummins QSB4.5, QSB6.7?
The primary fuel filter part number is 3978040 (Fleetguard/Nelson FF5421). The fuel filter (prefilter with WIF sensor) part number is 3973233 (Fleetguard/Nelson FS19732). When installing, tighten the filter 3/4 to 1 turn after the gasket contacts the filter head surface. p. 312
What is the valve clearance specification for the Cummins QSB4.5 and QSB6.7 engines?
The valve clearance for the intake valve is 0.254 mm [0.010 in], and for the exhaust valve, it is 0.508 mm [0.020 in]. p. 305
What is the torque spec for the M10 capscrew on the pad mount alternator of a Cummins QSB4.5, QSB6.7?
The torque specification for the M10 capscrew on the pad mount alternator is 36 N•m [27 ft-lb]. p. 125
What is the oil capacity of a standard Cummins QSB4.5 or QSB6.7 engine with a deep sump oil pan?
The oil capacity for a standard QSB engine with a deep sump pan is 17 liters [18 qt] for the pan only, and 19.2 liters [20 qt] for the total system. p. 307
What is the maximum exhaust back pressure for a Cummins QSB4.5, QSB6.7 engine with an exhaust catalyst?
The maximum back pressure for an engine with an exhaust catalyst is 15 kPa [2.2 psi]. p. 310
How is this Cummins QSB4.5 Operation and Maintenance Manual delivered?
You get a 342-page searchable PDF that downloads instantly after checkout. Open it on your laptop, tablet, or phone, and bring it right to the shop floor.
Is printing allowed for this Cummins QSB4.5 Operation and Maintenance Manual?
Zero restrictions. The PDF is DRM-free. Print whatever sections you need to take out to the shop. Standard letter or A4 paper works.
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