It’s the loss of power when driveing that’s puzzling me as no prior warning lights It just lost power then cut out & now won’t crank over
It takes three things to cause the bang in a Diesel engine: diesel, air and compression (to ignite it)
Lack of diesel can be caused by a variety of issues anything from "is there any in the tank" to "is there any getting to the injectors".
This in turn can be caused by a, or more than one, blockage to the fuel. Or by lack of sparks to pump the diesel up to the injectors and then to be injected into the cylinder at the right moment. This inevitably involves the ECU as well.
The air is sucked and then blown into the cylinder via the induction system, i.e. air filter, tubing, and then the turbo, via the intercooler. Not common to find a problem there, althougha massively blocked air filter could cause it.
Compression is caused by the engine turning, that could stop suddenly if you lost drive as in hydraulic lock, but that would be quite sudden. Lack of compression can also be caused by either valves opening at the wrong moment or the rings on the piston being knackered, but yet again unlikely to happen gradually.
You did say it lost power gradually which is why i posted as I did. Sediment building up in a fuel line/filter/etc could be gradual, was the tank low? Has the fuel system been checked at all?
Sparks come from the batt, but need to be replenished via the alternator, if the drive belt broke you'd probably spot that quickly as you would get heat building fast due to the coolant pump stopping working and you'd see that at first from the temp gauge then later from the steam and worse. You can see the drive belt very easily and check it.
Brushes on the alternator can wear or come loose which would cause it to generate less or no current. Also the diode pack can play up and thus lead to the same effect. So, while the batt has power it will keep the engine going but as it dies the engine will slow done as it is no longer providing enough power to all the stuff mentioned above.
Now I am an old skool spanner waver and although this is correct for older vehicles, it is possible that there are other factors or things I have said that are not longer true so please be gentle with me if I am wrong. But checking the alternator once you have got the car running is a first step.
If you cannot get the car started via the batt, jump leads etc, then ensure you can at least turn the engine over by hand with a spanner on the end of the crank, if you cannot do that then there is something seriously wrong in the cylinders. Which would mean they were not getting sufficient lubrication or they got too hot in someother way, lack of coolant maybe. But I do think this is unlikely.
If all connections to the engine from the battery, i.e.all earth leads are good and the connections to the starter are sound, as mentioned above by JM then the starter should turn, unless it itself is faulty, but you said a new one was fitted recently so this is not likely.
Incidentally, if the batt is dead jump leads aren't always as good as you would think they would be. You do not always get a decent contact. But while we are there, do ensure the contact between the terminals and the leads is good. The TD5 has a particulalry stupid design. You need to completely undo the nut on each one then bang the connection down the terminal with a socket or similar to ensure it grips it completely when you tighten it up. The vertical design using a bolt verticslly means tightening it is only too likely to simply twist the fitting around the terrminal.
Best of luck!
