Unhappy Engine Noises

Michelle pokes her head out from underneath the train.
I think that's it.
She puts a large piece of leftover hose aside and crawls out.
That was quick – nice job.
Jack walks over to the compartment holding the batteries, takes the cables off the terminals, and hooks them up to his makeshift power supply. Then, he starts the generator and climbs into the train. Michelle follows him and they go to the driver's cabin. Jack turns a key switch and parts of the dashboard light up. Then, he pushes the engine start button. While holding it, he points to the fuel pressure gauge and, slightly raising his voice to talk over the noise of the engine turning over, he says:
That's progress already.
The needle on the gauge slowly creeps to the right.
Too slow though, he adds after a moment.
He holds the button for a while, the engine keeps turning over, but it doesn't seem to fire even once.

Michelle suggests they take a look at the fuel injection. Jack turns the key switch off again and they go to the middle of the railcar. The floor panels above the engine bay are already missing, they had removed them earlier to replace the bits of rotting hose in the fuel line. Jack grabs the manual from one of the seats and starts flipping through the pages while Michelle jumps out and stops the generator. He begins to undo knowledge gap here: How does that work? What do you undo to fix a gunked-up fuel injection? Also, do/did diesel engines have a carb?

After cleaning out gunk and doing some makeshift fix, they try again. The engine attempts to start a few times but it still doesn't run. Michelle notices the fuel pressure is back down to zero so they pull the line out to see what's going on. Michelle waits next to the train, holding the end of the fuel line over a bucket while Jack returns to the driver's cabin. suggestions for improvements welcome

He presses the button for a few seconds, then he leans out of the window looking at Michelle and the bucket. She looks up at him and says:
Barely a few drips. But there's pressure on the other side of the fuel filter.
So we need a new one?

He walks over to the closest door and jumps out. Michelle begins undoing the clamps holding the fuel line to the filter while Jack starts searching all drawers and boxes in the vicinity for a replacement. One side of the filter comes loose and Michelle starts with the other side.

Not the right one but I found this.
Jack holds up a small box he found in a drawer. He opens it while walking back to Michelle and pulls out a fuel filter that is significantly larger than the one pulled from the train.
The hose fits inside the filter so they install it by putting a bigger hose around both.

Michelle climbs back inside, Jack starts the generator again and follows her. They go to the driver's cabin.
Ready? She has her fingers on the engine start button.
Go for it.
It takes a while but the engine eventually sputters to life. Michelle lets go of the button and it keeps running.