If the engine turns over the batteries are fine. Diesels require special equipment to troubleshoot, take it to a shop that is competent in diesel engines.
are you getting fuel past the fuel filter. do you have spark at the spark plugs
timing belt probley comon thing
I checked fuses and replaced blown fuses and now it won't start.
The timing or crankcase sensor needs to be checked and most likely replaced.
battery need to be at lease 14 volts to be able to start
You need to be more specific. Year, make, model, engine. There are dozens of things that it could be
i replaced the steering column and the fuel filter. the radio was stolen
If it's not cranking at all, you probably forgot to connect a wire, or you replaced the wiring incorrectly.
first have batteries checked one bad battery will mess up the computer next check fuel filter and water trap check coolant level and sensor
Could use a lot more info like year and model. Have you changed the fuel filter? Have you done a fuel pressure test? Could be a faulty fuel pressure regulator. Have you checked the fuses for the injectors and ecm? Have you checked the fuel pump relay?
What do you mean by not doing the job?? Do you have a loss of power, wont start?
If you didn't fill the new filter up with clean diesel fuel when you assembled it, you introduced air into the system.