here are some numbers
Autoignition Point of Selected Substances

* Silane: <21°C (70°F)
* White phosphorus: 34°C (93°F)
* Carbon disulfide: 100°C (212°F)
* Diesel : 210C (410F)
* Gasoline: 257°C (495°F) or 246C (474.8F)
* Butane: 430°C (806°F)
* Magnesium: 473°C (883°F)
* Hydrogen: 571°C (1060°F)

I am guessing a full size diesel truck engine would reach the auto ignition temp of gasoline. it seems like mixing gas and diesel would make it harder to ignite in the model.

i built a flame thrower out of a yard spary tank and I used to mix gas and diesel 50/50 and it was much easier to light and keep the stream lit well. With straght gas it was scary and straight diesel it burned too slow unless I turned the nozzle to spray a mist but then it was a flame thrower

I still think a bigger 18cc or so engine would do much better with a good bit more air volume to compress. its still about 2.5 times as big as a .40 engine.