The first thing I would do is turn the key switch to ON. Verify you hear the distinct "clack" of the stop solenoid retracting. Wait a few seconds and turn the key OFF and verify you heat the distinct "clack" of the stop solenoid extending (which would stop the engine if it was running). If you don't get the second clack, the stop solenoid is not holding in the retract position (hold coil) which could be a bad fuse.
A simple test for the stop solenoid (SS) if to remove (unbolt) the solenoid and see if it will start. Just be prepared to stop the engine with the manual shutoff if it starts. This stop solenoid must be retracted (or removed) to allow the engine to run. If the engine starts and runs with the stop solenoid removed, there are several possible root causes (bad SS (rare), bad "pull" relay (common), bad fuse, etc.) but it's an easy fix once you isolate the cause
With the SS removed, the injection pump rack/pin should move all the way forward (under light spring pressure) to rest against the governor arm. You should also be able to slide it aft with moderate finger pressure through the removed oil fill plate. If it's jammed and won't move you likely have a failed injection pump gear (control sleeve). You can also losten one of the "nuts" on an injector to see if any fuel comes out when the engine cranks.
Other non IP "no start" causes include: glow plugs may not be working, lift pump, fuel not reaching the injection pump, air leak in the fuel line, etc.
If the injection pump has actually failed again, don't despair. I believe the current replacement control sleeves (the things with the gear teeth that break) are improved but these improved ones probably were not available when your IP was previously rebuilt. The actual IP rebuild is very easy but also easy to do wrong if you are not careful. The needed IP rebuild parts are less than $100 from most Zexel (formerly Bosch) shops.
Removing the old IP is the hard part. You'll need to remove or externally secure the hood because the bracket for the hood strut must come off. The injection hard lines must be removed and there is little space to get a wrench on those nuts. The intake manifold must come off and you'll want to have a new manifold gasket on hand. You need to remove the pre-load assembly to the left (aft) of the IP and the SS to the right (forward) without dropping the plastic "hat" into the crankcase. Disconnect and clamp off fuel hoses to the IP so fuel doesn't drain.
At that point removing the IP is simply a matter of unscrewing the bolts and nuts. When the IP is rebuilt, all the old parts need to go back in exactly the same place; for example, the plunger and roller tappet from cylinder #1 need to go back into cylinder #1. If you do that and keep the old IP shims, the IP does not need to be calibrated or the injection re-timed after rebuild.
If you are not confident in your ability, any mechanic should be able to remove and install the IP and any Zexel shop should be able to do the rebuild, quite inexpensively (compared to a new IP). ThePumpGuySC would probably be happy to do the rebuild; he was an enormous help to me with technical advice when I rebuilt mine this spring.
