I think diesel technician is a good STEM career because there are a lot of benefits to it. They work a lot with there hands. The only bad thing is that you work on random or late-night shifts. Also you may encounter accidents or injures you don't need a whole lot of schooling. You also manly learn on the job.
As a diesel engineer you do work 40 hours a week sometimes more. The average starting salary is about $35,000 a year but it does depend on your education level. Post-secondary training is only 6 months to a year.