Nowadays, biodiesel fuel has been promoted to Thailand agricultural sector in order to reduce the use of petroleum diesel fuel and the energy cost in small communities. The first target is to promote the use of biodiesel in single cylinder diesel engines, which have been used in several agricultural activities such as farm irrigation, electricity generation and agricultural machinery. Hence, this research aims to investigate the changes in engine performance, fuel consumption and black smoke emission of a 14-hp single cylinder diesel engine after a working period of 1,000 hours using pure biodiesel as the tested fuel. The engine was connected to a centrifugal pump to circulate water that performed as engine load. During the test, fuel filter, injector and hoses were investigated. Both diesel and biodiesel were tested with the engine after 1,000 hours of biodiesel, the biodiesel results suggested similar power and fuel consumption with less black smoke amount than the case of diesel. When considering the effect of biodiesel fuel at 0 and 1,000 hours, the engine produced more power and torque outputs while black smoke suffers from typical wear out of 1,000 hours usage time. There was no major problem detected by performance evaluation, however, the part investigations showed some deposit built up on the nozzle tip. Other parts are still in good condition