Caterpillar 3116

The Caterpillar 3116 is a bare industrial diesel engine, not a mobile machine: a 6.6 L (403 cu in) inline-six, four-stroke, direct-injection diesel with a 105 mm x 127 mm (4.13 in x 5.00 in) bore and stroke and a compression ratio of roughly 16:1. Caterpillar built it in naturally aspirated, turbocharged, and turbocharged-aftercooled (TA/DIT) forms, most running a mechanical unit-injection fuel system with a hydra-mechanical governor; a smaller run late in production switched to hydraulically actuated electronic unit injection (HEUI) with an ECM. Industrial-duty ratings run roughly 82-160 kW (110-215 hp) depending on configuration, with separate generator-set (around 100-125 kW standby), highway-truck (127-186 kW / 170-250 hp), and marine propulsion (112-224 kW / 150-300 hp) calibrations sharing the same base block. Bare engine dry weight runs around 680 kg (1,500 lb); a package's shipping weight depends entirely on what is bolted to it. Caterpillar built the 3116 from roughly 1988 into 1998 as part of the 3100 engine family alongside the smaller inline-four 3114; the 3126 succeeded it in 1998 and was itself later updated into the Caterpillar C7. Beyond stationary industrial duty — generator sets, pumps, air compressors, irrigation and dewatering drives — the same block also powered construction machines, medium-duty trucks and buses, and marine auxiliary and propulsion packages.

Across the 3116's run, the biggest change was the fuel system rather than the base castings. Early and most mid-production engines use a fully mechanical, camshaft-driven unit-injection pump with a mechanical governor, manual valve-lash setting, and static injector timing; later production added HEUI, which uses engine oil pressurized to roughly 20,000 kPa (3,000 psi) to fire ECM-timed injectors and removes the manual timing procedure. Very early production also carries a known block heat-treat defect, showing up as high oil consumption and heavy blowby inside the first 150-200 hours; Cat covered most of these under warranty decades ago, so any engine well past that window is clear of it. The 3116 stays active in today's used and rebuild market because industrial and generator-set operators still value a mechanically governed diesel a field mechanic can service without a dealer scan tool, because parts commonality runs across the wider 3116/3126/C7 family, and because the block remains a common repower and pump-drive or genset rebuild candidate wherever simplicity and parts availability matter more than emissions certification.

Below: full specifications, fluids & capacities, the factory service schedule, common service parts, verified fault codes, what owners discuss, attachment guidance, the complete assembly directory, and a serial-number reference. Complete parts lists with full OEM part numbers, exploded diagrams, quantities, and fitment data are available free in Heavy Parts AI.