I imagine that there will come a time when they’ll need to revert to horse and wagon transport at the site. Or perhaps lay down railroad tracks and use cable cars.
Up until the 2000s diesel engines in cars used mechanically controlled injection. With those, once started, the engine will run without any electronics.
Engines produced for industrial applications (such as tractors) in developing countries still use this, as it's a lot simpler and more reliable. Military trucks are the same. Just don't tell the EPA.
It is possible, but fortunately still exist countries like Ukraine, and produce old diesel engines for trucks (KRAZ) and for tanks (T-64 line, including T-90, and also used on military trailers like MAZ-537, so when you cannot visually see, you don't know if tank running itself or on trailer).
Main problem, in those countries have not managed to produce small diesel engines for light trucks, and KRAZ engines are something 6L or more (tank diesel are 10L).
I hear they made half-block near-flat modification for armored personnel carrier, and even used it on low-floor city bus, but as I know they was not much market success, so have not produced big series.
In eastern Europe in 80-90s produced small trucks with analog diesel engines, but as I know most enterprises already scraped and most lucky now producing WW or Renault by license.
I have a 10kW diesel motor that doesn't have any wires at all, no battery. It's my SHTF generator for my well.
I might have to wind a generator motor if the reason stuff went bad is because of emp, but otherwise, yeah, you can buy 100% mechanical diesel engines still.
