This article reports experimental and developmental studies on a producer gas/diesel dual fuel operation of a small engine for irrigation water pumping. In this work, a biomass gasifierengine system was designed, built, and tested. Waste woods from the furniture-making industry and charcoal were used as feedstock to produce fuel gas in the downdraft, throat-type, fixed-bed gasifier. The engine performance was evaluated over a fixed load and variable speeds between 1,0002,000 rpm. Results showed that dual operation was able to produce slightly higher power output than normal diesel operation, with similar thermal efficiency. Producer gas substitution or diesel replacement of about 6070% by mass was achieved. The producer gas powered water pumpset was later installed at a farm in rural Thailand. Start-up was straight forward and continuous operation was achieved with a water yield at 60% of nominal value. It was successfully demonstrated that biomass gasification could provide clean fuel to a small engine and this renewable energy technology could be a sustainable option for water pumping in rural areas.