Not Running Diesel Engine (mechanically controlled)
If the engine is turned over fast enough by the starter, but does not start, the history of the vehicle is significant so that you know where to turn. The first important question is when the engine has been running for the last time and whether there have already been indications of an upcoming failure. The worst is if you do not have any information about the functioning of the engine. Very interesting would be whether there has recently be a reparation of the fuel injection system or glow equipment and the engine quit starting afterwards.
How it works
It must be pointed out that all starter tests should be done very shortly to spare the starter and the battery. The first hint is provided by slightly opening the single injection pipes at the nozzles. If fuel comes out at every single spot, the fuel supply is first of all considered operative. The error analysis proceeds with: - the nozzles, - the compression, - the glow equipment.
Having no further information about the vehicle, a garage would carry out either a resistance measurement at the glow pins, or dismount the nozzles and examine them. Besides, a thorough compression check would be possible, too. If these possibilities are not present, maybe a dragging along period of the vehicle might help. In spite of an absolutely defective glow equipment, it is possible to get an engine with a fairly intact fuel injection system to running.
If the engine runs steadily after such a forceful act, the glow equipment should be examined very carefully. Doing this you might disconnect gradually single glow pins and measure its resistance. If no other documents or information of the car exists, you can estimate the current bearing at the fuse. In case of 30 - 50 A for 4 cylinders 1 ohm in cold state is an educated guess. Defective glow pins can be exchanged in general individually.
If the engine run is unsteady, your workload is increased. The engine should undergo an exact compression test and perhaps further reaching tests. If no mistakes are discovered, a check of the beginning of delivery might also help. The easiest way is via the clamp-on transducer and the help of a stroboscope lamp. However, if no reparation has taken place of the fuel injection system recently, the nozzles should be checked next. They are checked extensively, the question that should be answered afterwards is whether to replace them or to repair them.
In the end the question must still be answered what should be done if the injection pipes submit no fuel. Besides the fuel gauge an electric or even maybe mechanical shut down mechanism should not be ruled out. Maybe the electric shut-off valve is not provided with 12 V. Next is the fuel delivery pump. An opening of the runback might help. Starting the engine, there should be fuel in larger amounts at the runback coming from the pump. If all this does not give a result, an exchange or repair of the pump is very likely.
Quality information about the vehicle, its recent reparation history and the mistakes can decisively shorten the error analysis time.