Internal combustion engines (ICEs) powered by liquid fuels remain the dominant powertrain system for heavy-duty road transportation, benefiting from the high energy density, ease of storage and transportation, and relatively low refueling pressure of traditional liquid hydrogen carbon fuel. However, concerns over tailpipe emissions and greenhouse gas (GHG) effects have driven the search for alternative fuels with lower carbon footprints. ICEs offer a key advantage during this transition, as they can operate on a variety of fuels, enabling a flexible approach to reducing harmful emissions and GHG while maintaining reliable power output. Alternative liquid fuels, such as dimethyl ether (DME), have shown great potential in mitigating environmental impacts while ensuring sufficient engine performance. However, the significantly different physical and chemical properties of renewable fuels necessitate the adoption of tailored combustion strategies to ensure optimal engine operation. In particular, the fuel injection strategy plays a pivotal role in governing the combustion process, as it directly influences fuel-air mixing, ignition characteristics, and hence, the combustion efficiency. Therefore, detailed characterization of the fuel injection process (rate of injection (ROI) profiles, injection delay, and injection quantities) is necessary for research and development of advanced combustion strategies. In this study, the ROI profiles for diesel, DME and polyoxymethylene dimethyl ethers (OME3) were measured using the Bosch long tube method, with diesel severed as the reference fuel. Comparative tests were conducted under varying injection pressures (300 bar to 900 bar) and injection durations (0.3 ms to 3 ms) to investigate the influence of fuel properties on ROI profiles. The results revealed that all three fuels exhibited comparable ROI at injection durations below 700 µs. However, at longer injection durations and higher pressures, significant differences emerged. At a 3 ms injection duration, DME consistently showed the lowest steady-state ROI, while OME3 exhibited the highest across all injection pressures. Furthermore, the discharge coefficient (Cd) increased with injection pressure and converged across three fuels at higher pressures. This indicated that, under those conditions, fuel density became the dominant factor influencing ROI, hence the injection quantities.