## 1 Introduction
As shown in Table 1, when evaluating the safety and reliability of a new system, the combination of FTA and FMECA has been a necessary step at the design stage, but this technology has only been applied at the \"primary stage\". In another study, when the comprehensive application method of FTA-FMECA was used to evaluate the reliability of a robot system [38], it could not be fed back in time in the later reliability analysis, thus highlighting the reliability problem of the system throughout its whole life cycle. In addition, this technology lacks comprehensiveness in terms of all of the risks in the analysis of different safety and risk assessments [39]. It can be inferred from the literature that the design stage of a new vehicle diesel engine needs to systematically identify risks and provide timely feedback across its whole life cycle. For the fault analysis of newly developed highly complex systems, only using a single \"F\" technology often leads to the following difficulties: when FMEA is applied to a complete system, it may be difficult to achieve a sufficient analysis depth to fully understand the \begin{table}
\begin{tabular}{c c c} \hline
**References** & **Tool** & **System** \\ \hline
[12] & FMECA & Diesel engine \\
[13] & FMECA & Vehicle \\
[14] & FMECA & Vehicle turbocharging \\
[15] & FMECA & Figure engine \\
[16] & FMECA and FTA & Power plant \\
[20] & FHA & Aircraft resistance runway \\
[21] & FHA & Aircraft control system \\
[22] & FHA & Aircraft flight system \\
[23] & FHA & Aircraft landing gear \\
[24] & FHA & New electric vertical lift vehicles \\
[25] & FTA & Automatic driving vehicle control \\
[26] & FTA & Diesel engine turbocharging \\
[27] & FTA & Diesel fuel system \\
[28] & FTA & Gantry crane \\
[32] & FRACAS & Ship weapon system \\
[33] & FRACA and FMECA & Shipborne combat system \\
[34] & FRACA and FMECA & Aviation industry management system \\
[35] & FRACAS & UAV \\
[36] & FRACA and FMECA & Rail vehicle \\
[37] & FRACA, FMECA, and FTA & Vehicle power system \\ \hline \end{tabular}
\end{table} 
Table 1: Assessment tools for system safety and reliability. fault behaviors; FHA pays too much attention to functions and often ignores other types of hazards; FTA has a heavy workload when analyzing a complete system; FTA relies too much on expert experience when setting top events; and a FRACAS is inefficient at evaluating failures when analyzing new systems. Therefore, the fault analysis of newly developed highly complex systems requires a more integrated hybrid method. In terms of the application of the existing \"4F\" technology, [PERSON] [40] expounded its necessity for the reliability analysis of new systems. Therefore, in this study, 4F integration technology was adopted for the reliability analysis of a new diesel engine in the design stage. This paper is the first to use 4F integrated technology to evaluate the reliability of a vehicle diesel engine. FMECA was used to identify the functional hazards of the diesel engine, FHA was used to evaluate the failure mode analysis of the diesel engine, the failure mode was quantified by FTA, and a FRACAS was used to manage the analysis conclusions of the above technologies. The purpose of this study was to evaluate the fault hazards of the diesel engine so as to formulate corrective measures to prevent accidents. In the upcoming sections, the methods that were used in the diesel engine reliability analysis are described and the main research results are introduced and then discussed.