I have a older 6bt in a piece of equipment, not original engine. It has always started instantly all of a sudden it won't start in the morning without a dose of starting fluid. It doesn't have any smoke when turning over, once started it runs fine and will start the rest of the day even after sitting for a hour. my guess is bad fuel shutoff valve.
Engine: 6bt cummins
Hello and welcome to Just Answer! I would be more than happy to assist you today.If the fuel shut off valve was the issue the engine would not start at all. You should start with the lift pump that is the most common cause of this. this is also a good time to change the filter.
Cummins field tech