420 D will not start

[spurs]

We have a 420 D cat backhoe that has plenty of fuel but will not fire is there a sensor somewhere that could be causing a problem? It turns over and white smoke is coming out of exquast pipe.
But just turns over and will not start.

 

[Bob Rooks]

If the smoke is snowy white then it is moisture = head / head gasket / liner / cylinder wall, etc.
If the smoke is more grey-ish / blue-ish that's unburned fuel from over fueling = dribbling injector washing down cylinder walls / liners and diluting the oil.
Suggest simplest tests first. Make sure all permissives are cleared if PLC equipped. Check coolant for combustion gasses. Check air filter for restrictions. Check injection pump timing. Perform a compression / leak-down test. Pop test injectors.