To enhance the efficiency of direct injection engines, the understanding of the combustible mixture formation after a liquid fuel spray is injected is crucial; hence, the need is readily apparent for experimental methods that allow determining characteristic parameters such as fuel/air ratio and gas temperature. The paper demonstrates the potential of the laser‐induced grating technique to determine simultaneously the local vapor phase fuel concentration and the temperature during the temporal evolution of a direct‐injected spray. The precision and the accuracy of the experimental approach and of the applied data treatment procedure were evaluated by using calibration measurements in a constant volume cell under known stationary conditions. The test measurements of fuel vapor concentration and gas temperature were carried out in an injection chamber using a high‐pressure swirl injector. Liquid propane as the main component of liquefied petroleum gas was directly injected into the chamber under flash‐boiling conditions. Injection and ambient pressure were varied, whereas fuel and ambient temperature remained constant. The measurements were performed inside the fuel jet at different distances from the injector outlet along the axis of propane injection. The results are indicative of small evaporative cooling of the gas in the jet. Copyright © 2013 John Wiley & Sons, Ltd.