Cummins N14 Diesel Engine Shop Manual – 1991 (P/N 3810487)

The Cummins N14 Shop Manual (P/N 3810487), printed in February 1991, covers stand-based engine rebuilding for STC and CELECT engines. The procedures identify differences that affect the work by engine model, application, optional equipment, and build year.

PDF Search, Bookmarks, and Page Count

Search and navigation: Embedded bookmarks link to the service groups and individual procedures. Most pages support text search. The cover and some tool, inspection, and exploded-view pages must be read on the page itself.

The download is one printable English PDF with 587 pages. The total includes the original cover, two literature order form pages, and two survey form pages.

Engine Teardown, Rebuild, and Run-In

This selection of shop procedures highlights the main rebuild work. The manual also covers cam follower roller replacement and replacement of the CELECT Metri-Pack pass-through connector.

• Engine teardown and assembly: Crankshaft, cylinder liners, pistons and connecting rods, camshaft and gear train, rocker assemblies, gear and rear covers, and vibration damper.

• Block and cylinder head: Counterbore and liner checks, main bearing bore alignment, connecting rod bend and twist inspection, valve and seat reconditioning, guide and injector sleeve replacement.

• STC and CELECT fuel systems: Fuel pump and injector installation, injector and valve adjustment, STC oil plumbing and control valve, and CELECT ECM, sensors, and harnesses.

• Lubrication, cooling, and drive units: Oil pump and oil cooler rebuilding, water pump and idler overhaul, thermostat housing service, and accessory drive repair.

• Air intake and exhaust: Turbocharger axial and radial clearance checks, intake and exhaust manifold inspection, and exhaust manifold slip-joint service.

• Post-rebuild testing: Oil system priming, engine and chassis dynamometer procedures, run-in without a dynamometer, and a worksheet for comparing performance readings with specifications.

• Illustrations and service data: The Cummins 22-Group System Exploded Diagram, block and head views, separate injector exploded views, and the lubricating oil system view supplement the torque, clearance, and capacity data.

This manual is intended for experienced heavy-duty diesel technicians and engine rebuilders with an approved engine stand, rated lifting equipment, precision measuring tools, and the fixtures specified for the job.

Block, Head, and Flywheel Inspection

Block procedures cover camshaft bushings and inspection of bearings, crankshaft, and pistons. The cylinder head section covers valve grinding, magnetic-particle inspection of the head, pressure testing after injector sleeve replacement, and vacuum checks for valve seating. The vacuum test helps determine whether the valve and seat seal well enough for reuse.

The assembly and mounting sections show how to measure flywheel and flywheel housing runout and when the housing needs realignment and redoweling. Listed tools include the ST-125 or 3822512 lifting fixture, the 3375194 rebuild stand with 3375013 adapter, the 3823451 injection timing fixture, the ST-1012 cylinder head test fixture, and the ST-1257 valve vacuum tester.

Fuel-System Setup and Engine Brakes

Engine identification: Use the engine serial number (ESN), Control Parts List (CPL) number, model, advertised horsepower, and RPM to match the engine build. The STC fuel pump and engine CPL numbers are checked against each other, and the separate CPL Manual (3379133) supplies engine-specific injection timing values.

STC and CELECT: STC uses PT Type D full top-stop injectors, an external oil circuit, and its own overhead setting method. CELECT coverage includes electronically controlled unit injectors, the ECM cooling plate, engine position and pressure and temperature sensors, and actuator and sensor harness installation. The dynamometer section also illustrates the CELECT test harness hookup.

Engine brakes: The shop manual covers C-Brake installation and slave piston adjustment. It refers Jacobs 440 (STC) and 445 (CELECT) installation and adjustment to separate Jacobs literature.

Separate Repair References

The manual directs general troubleshooting to Bulletin 3810456 and CELECT system troubleshooting and internal fuel pump work to Bulletin 3810469. Full wiring schematics are in Bulletin 3379099. PT fuel pump rebuilding and calibration, internal STC injector rebuilding, and air compressor rebuilding also use separate component manuals. Group 18 in this PDF is headed NT 855. Use the N14 procedures for N14-specific specifications.

Selected Head Test and Turbocharger Limits

The N14 cylinder head leak test specifies 275 kPa [40 psi] of air pressure with the head submerged in water at 60°C [140°F]. The procedure uses bubbles to locate leakage after injector sleeve work.

For the BHT3C turbocharger, the shaft axial clearance check specifies 0.03–0.10 mm [0.001–0.004 inch]. That range applies to shaft end play. Separate radial limits apply to the compressor impeller and turbine wheel.