The methods and principles of monitoring and diagnosing the parameters of power units are generalized. They allow increasing the wheeled vehicles operational reliability. Systems for monitoring the functional stability parameters of the most sensitive to operating conditions systems and assemblies of machines have been developed on the example of a cylinder-piston engine group and steering. An improved method for diagnosing the steering of an articulated wheeled vehicle, which significantly affects the safety of its use, is proposed based on the use of angular accelerations of sections in the road plane as a diagnostic parameter. The dependence for determining the angular accelerations for the case of the random installation of two sensors of the mobile registration and measuring complex on the machine, which allows increasing the accuracy of measurements, is obtained. Experimental studies to diagnose the steering of wheeled vehicles with various operating times have been carried out. It has been established that when running up to 6000 hours, the diagnostic parameter can be reduced to 15%.
Theoretical and experimental studies were carried out for the cylinder-piston group, which established that the amount of gas passing through the valve mechanism of the cylinder head is proportional to wear and amounts to 5-15% for new and 25-40% for repaired engines of the total crankcase gases. Using the obtained dependences, the method for assessing the technical condition has been developed, which differs from the existing with separation of gas flows passing into the crankcase through the gaps "valve stem - guide sleeve" and "sleeve - piston". Also the control system that allows to determine the speed and quantity of gases passing through these gaps in all operating modes of new and repaired engines has been developed. The proposed system allows increasing the accuracy of assessing the technical condition of the cylinder-piston engine group by 40%.