The use of new and innovative methods in the design of internal combustion engines is essential for the significant development of the automotive industry. In spark ignition engines with a conventional fuel supply circuit, the amount of fuel injected by the injector is strongly dependent on the pressure difference between the back and the injection location of the injector, as well as, the injection period. The pressure at the injection location cannot be controlled due to the phenomena of air flow disconnection and fuel evaporation fraction, and causes complications in estimating the amount of injected fuel. In the present work, a gas pressure fueling system (GPFS) was designed to estimate the mass of injected fuel per cycle. In this study, a single-cylinder research spark ignition engine under certain operating conditions was used, First, for a given injection period with the conventional engine fueling system (CEFS), experimental data of cylinder and intake manifold pressures, TDC, and crank angle were extracted for more than 550 consecutive cycles. Then, using the GPFS method at different gas pressures, in addition to the aforementioned data, the fuel volume consumed for more than 2500 consecutive cycles was measured and stored. With this method, the fuel injected per cycle was estimated. A lot of effort was made to find a case that would provide similar performance to the CEFS method, and an experiment in which the gas pressure was 0.25 bar higher than the CEFS line pressure was found to show relatively similar performance of the CEFS case. The data of these two cases have been examined and compared in this study. The results showed that the GPFS method, with an increase in pressure of 0.25 bar, had similar performance to the CEFS method, meanwhile it was also possible to measure fuel mass per cycle.