A laboratory investigation was conducted on the utilization of neat methanol and glow plug ignition in direct injection four cycle diesel engines. Two engines were used in the investigation: a single cylinder engine, and a heavy duty six cylinder engine. The principle goals of the investigation were to obtain emissions data for this type of engine, and to identify engine configurations (i.e., piston shape, injector design, combustion chamber swirl, injection timing) that were effective in reducing emissions.The single cylinder investigation found that the interaction of injector sprays with the piston bowl and the glow plug, had a strong effect on engine emissions. Impingement of fuel on the surface acted to reduce oxides of nitrogen (NOx), but to increase hydrocarbon emissions. The addition of swirl tended to reduce hydrocarbon, but increased oxides of nitrogen emissions.Engine operation was demonstrated over the entire speed and load range on the warmed up multi-cylinder engine, with glow plugs turned off, indicating compression ignition. On both glow plug ignition and compression ignition, engine operation was sensitive to the injection timing. Preliminary transient tests indicated that the multi-cylinder engine could produce NOx emissions below the EPA 1994 Standards. These tests also indicated unacceptable hydrocarbon and carbon monoxide emissions. It is likely that hydrocarbon and carbon monoxide emissions can be significantly reduced through improved control of injection timing, and through further improvements to the piston/injector design.