Actually diesel fuel mist will ignite with a spark at room temperature.
The old (and still often used) fuel oil furnaces are routinely set up to run on diesel fuel and they are spraying room temp diesel fuel across a spark gap that easily ignites it. Many of the more modern oil furnaces shut off the spark gap a few seconds after the fuel is ignited and the fine spray holds a self sustaining flame.
By adding an air source (bubble atomization principle) to the fuel spray coming out of the nozzle thicker fluids like used motor oil will in fact ignite quite easily and can also still hold a self sustaining flame as well. Used oil burner systems typically work this way.
Its why I still suggest the added precautions with any atomized fuel mists. They may not flash ignite as easily as gasoline vapor but still they can ignite rather easily with far less ignition source energy than most think.
Either way you get a big hot flash thats at minimum rather surprising for a result.
If the OP manages to fire a fuel injector with 1600 Bars pressure on it there will be an incredibly fine mist produced that will ignite very easily.