An experimental work has been conducted to investigate the ignition of n-heptane in the ignition quality tester (IQT TM) by using fine gage thermocouples. A set of eight buttwelded exposed junction thermocouples (TCs) were inserted inside the chamber of IQT TM at different preselected locations to get the temperature variation spatially and temporally in the period prior to the fuel injection up to the mixture ignition. The data were recorded by using a high frequency data acquisition system with a sampling rate of 10 kHz per channel. The experimental data were characterized at set point temperature 584 o C and pressure 21.3 bar. For reproducibility purposes, 32 injections have been averaged and presented. A drop in temperature due to fuel spray cooling effects has been recorded by TCs at the chamber centerline whereas TCs near the chamber walls did not show a significant drop in temperature. Thus, there was no evidence that the fuel spray reached the chamber walls. The measurements showed that the combustion occurs in the main part of the chamber and the region near the fuel injector nozzle did not show a significant rise in temperature.