1991–1997 Kohler Command CH18, CH20, CH22, CH25 Engine Service Manual (P/N TP-2428-A)

This Kohler Command service manual, Form No. TP-2428-A, covers maintenance, diagnosis, and repair for 1991–1997 CH18, CH20, CH22, and CH25 horizontal-crankshaft engines. Separate sections address LPG fuel systems and the CH26 electronic fuel injection system.

• Engine repair: Complete disassembly, cylinder-head and valve reconditioning, piston-ring service, hydraulic-lifter priming, camshaft timing, and engine reassembly.

• Carburetors and governor: Keihin carburetor overhaul, float-height adjustment, fuel-pump testing, and mechanical governor adjustment, with separate procedures for LPG and EFI configurations.

• EFI diagnostics: Motronic ECU fault codes, sensor and injector tests, fuel-pressure checks, TPS initialization, wiring diagrams, and connector pinouts.

• Ignition and starting: CD ignition and Smart-Spark diagnosis, charging-system tests, electric-starter repair, and retractable-starter disassembly and recoil-spring tension release.

• Lubrication and cooling: Gerotor oil-pump and relief-valve service, Oil Sentry testing, maintenance intervals, oil and filter changes, and air-cleaner and cooling-system care.

The overhaul procedures and electrical tests suit mechanics experienced in engine measurement and circuit testing; LPG service is expressly reserved for qualified LPG service providers.

Engine Reconditioning and Model Differences

Cylinder leakdown testing helps distinguish ring leakage from intake- or exhaust-valve leakage when automatic compression release makes a conventional compression reading unreliable. The manual identifies leakdown tester P/N 47 800 02 and provides a results chart, alongside crankcase-vacuum testing and troubleshooting for starting difficulty, overheating, and power loss.

CH25 cylinder repair: The POWER-BORE cylinders described in this edition cannot be resized or honed using the CH18–CH22 procedures. For damaged CH25 bores, the manual specifies a replacement miniblock or short block.

Crankshaft thrust-bearing specifications distinguish CH25 engines below serial number 2403500008. Reassembly coverage also separates early hollow push rods and their rocker arms from later solid components, and explains gasket, RTV, and O-ring valve-cover configurations.

Engine-dimension drawings and torque, horsepower, and fuel-consumption curves supplement the inspection tables. Flywheel installation notes explain how lubricant on the mating tapers can overstress and damage the flywheel.

Carburetors, LPG Equipment, and Governor Service

The gasoline section covers Keihin fixed-main-jet carburetors, including accelerator-pump versions, fuel shutoff solenoids, and float adjustment. The carburetor exploded view identifies the components involved in disassembly and repair-kit installation.

LPG configurations: Coverage distinguishes Impco and Nikki carburetors, the vaporizer, electric lock-off/filter assembly, and Impco (Beam) and Nikki regulators. The carburetors and regulators are not interchangeable between the two systems.

Regulator coverage explains operation and general service; detailed rebuilding instructions are supplied with the respective rebuild kits. The Impco carburetor’s calibrated load block is not internally serviceable.

CH26 EFI Diagnosis

The dedicated CH26 section separates metal-cased and plastic-cased Motronic ECUs, with their respective connector pinouts and wiring diagrams. These controllers are not interchangeable.

Diagnostic coverage includes the engine-speed, oil-temperature, oxygen, and throttle-position sensors, plus injectors, ignition coils, the fuel pump, and pressure regulator. An oxygen-sensor cutaway explains sensor construction; the troubleshooting flowchart and fault-code descriptions connect operating symptoms with the relevant circuit checks.

TPS initialization and the EFI-specific initial governor adjustment receive separate procedures. Fuel-pressure testing identifies pressure tester P/N 24 455 04-S. Service notes also explain how connecting or disconnecting electrical components with the ignition on can send damaging voltage spikes through the ECU.

Ignition, Charging, and Starter Repair

The electrical section distinguishes standard CD ignition from the Smart-Spark system used on CH22 and CH25 engines. Wiring diagrams for the 15-amp and 25-amp regulated charging systems accompany stator and rectifier-regulator tests.

Starter coverage distinguishes UTE and Eaton inertia-drive units from the Nippendenso solenoid-shift starter, including their different brush-service arrangements. Observe the manual’s precautions for retained fuel pressure and stored recoil-spring tension.

Examples of Valve and Assembly Specifications

These examples show a small selection of the valve and fastening data provided for the covered CH18–CH25 engines.

The specification tables list a minimum intake-valve lift of 8.07 mm. Breather-cover fasteners have a specified torque of 8.6 N·m with either RTV sealant or the formed gasket.

Cylinder-head installation uses an initial 20 N·m tightening stage and a final 40.7 N·m stage, together with the illustrated tightening sequence. The manual presents these as part of the assembly procedure, alongside inspection limits and component-specific clearances.

PDF Navigation and Included Pages

Text search and diagram detail: Text search is available in portions of the fuel-system sections. Embedded bookmarks navigate the main chapters and the LPG and EFI sections. Small labels in the EFI wiring diagrams require zooming.

Delivered as one printable, 184-page PDF in English. That total includes the 12-page LPG section, the 39-page CH26 EFI section, and the front cover, contents page, and back cover, each one page.