It will not run with diesel.
68 degree Celsius
As low as 126 degrees Fahrenheit, diesel fuel could potentially catch on fire. This is known as the temperature of ignition.
According to my manual, the fuel light goes on when the tank is down to approx 6 litres of diesel.
Probably not but why is it in there and how much?
No, diesel fuel is not easy to set on fire. It has to have a good wick, or be vaporized to be quickly set on fire. You can put out a match in a pool of diesel fuel, but you wouldn't want to drop a match into a tank that holds it, as enough may have evaporated to cause it to ignite. It is not as volitile as gasoline.
Yes you can mix oil and diesel for burning brush and stuff just don't put it in any engines!
Diesel fuel is not very volatile. It's very unlikely (I hesitate to categorically state "impossible") that it could be ignited by a cigarette.
Yes it can if the fuel gets hot enough to ignite as in leaking on a header.
My Mk3 fiesta did not.
The sparks plugs fire and ignite the fuel in a Gasoline engine, and compression compresses the fuel until it ignites in a Diesel engine.
water sensor has malfunctioned/or fuel has large quantity of water contamination.