Why can I smell diesel fuel when I am driving down the road with the heater or a/c on???

 

might check your fuel rail i kept seeing fuel mist on the tailgate of my truck after long drives or pulls and noticed at the base of my #6 injector line had a wet spot tried to tighten still leaked when i put gauges in my truck i musta bumped it just right cause it started pouring fuel out just a thought for something to check

 

most likely a diesel leak, check that stuff out, especially with the price per gallon going up