In this study, the effects of fuel injection pressure on the performance and exhaust emission characteristics of a single cylinder, constant speed, direct injection diesel engine have been investigated and compared with diesel. The engine fueled with Jatropha methyl ester (JME)-Tyre pyrolysis oil (TPO) blend (JME 80%+TPO 20% on a volume basis), was run at five different fuel injection pressures (210, 220, 230, 240, and 250 bar) in addition to original injection pressure of 200 bar. The results confirmed that the injection pressure up to 220 bar gave better results for the JMETPO20 blend in terms of performance and emission characteristics compared to those of original injection pressure and also 230, 240 and 250 bar. At 220 bar injection pressure, for the JMETPO20 blend the brake thermal efficiency was higher by about 5.12%, and the hydrocarbon and carbon monoxide emissions were lower by about 1.75% and 6.2% respectively compared to original injection pressure at full load. The smoke opacity was lower for the JMETPO20 blend at full load by about 9.5% at 220 bar compared to original injection pressure.