Dear customer, the ignition failures are very common with the passing of time, a diesel engine needs four important components for its proper functioning and ignition:
-High fuel pressure
-High compression in the cylinders
-Good air inlet to the cylinders
As you can see, there are diverse factors to examine.
First, I'm going to recommend you to purge the fuel system, injector by injector, this process is very simple you just have to open the diesel screw of each injector and pump until fuel comes out constantly, you must perform this injector step by injector.
Then measure the compression of the cylinders with a compression gauge that should be around 150 kPa (21.75 psi) and should be equal in the 4 cylinders.
Also given the mileage if you have not replaced the fuel tank pump, I recommend you consider replacing it you can also measure the state in which the pressure is, but these pumps are the main cause of lack of fuel for ignition in diesel engines .
I recommend you replace the glow plugs, they have already passed more than 50000 miles and it is necessary at this time and at this mileage.
If the turbo is working in a faulty way the vehicle will not start because it does not have a good fuel input so once you have checked all the above, check the turbo
Finally Dear Customer. If all these factors have been checked, please note that starting the vehicle by applying a little fuel or starter liquid by the air intake, if the vehicle turns on this way so for a few moments you are going to be presenting a problem in the injection pump so you will have to disassemble and verify it. before check the injection pump, verify first the aspect mentioned above.
Another problem is that if the fuel rail fuel injection pump has a small intake i.e air is hermetically sealed, the vehicle will cost too much to start because it will never be correctly purge the injectors, and can effectively be misinterpreted as a faulty injector but not it's like that, you simply have an air leak that does not let the system purge.