Accidentally reversed connections to fuel regulator

Like a muppet I accidentally put the lines from the fuel cooler and fuel pump in the wrong way round when I fitted a new fuel regulator on my TD5. I was changing the pressure regulator as the fuel pump had started to scream (because it was pumping air?) and I knew the regulator was leaking so it was the first thing to change. With the pipes reversed, I went through the fuel purge techniques and the fuel pump settled down and went quiet after a while but obviously the engine wouldn’t start.
I’ve corrected the error and repurged the system but it still won’t go. Have I done some permanent damage somewhere?

One fault still remains which is I used the existing return fuel return pipe from the front end of the head (how in earth do you access the union hidden away to undo this pipe!!) and I’ve noticed that one of the rubber pipe to metal joints is seeping diesel. As it’s on the return pipe I’d assumed this wouldn’t stop the engine starting but perhaps I’m wrong?

Purge it more than once and if it still doesnt start use some spray to get it running on that and eventually try to bump start it then if there's an air lock it should get rid of it... I dont think that there's any damage just an air lock

I've listened again and there seems to be some strange gurgling sounds coming from under the rocker cover as it's purging air from the system. Is this normal?

Might be normal. If there is an air-lock the auto-purge can't always dislodge it you'll have to get the engine started for that with spray or towed ... provided you are 100% certain now that the pipes are well connected

I'm 100% certain they're correct now. The line from the tank (and pump) goes to the upper hole and the line from the fuel cooler goes to the lower hole in all the fuel diagrams I can find and that's how I've configured it.
It was late and getting dark and I only took the lines out to allow me to get access to the tricky third bolt underneath. (Not a bolt now as my local Landy dealer had given me a top tip which was to replace two of the bolts with studs; makes it a lot easier to fit the new tin gasket and pressure regulator.). I'm still annoyed with myself that I could make such a stupid mistake.

Thanks for the tips. With a couple of squirts of starter aerosol into the snorkel I’ve managed to start the engine. The downside is that the pump is still screaming away and is obviously still sucking air in from somewhere. Tank is half full.
Filter and it’s mount and then injectors next I suppose? Any hints as to how one finds where in the system it’s leaking?

Replace the air bleed valve in the rear outer port of the filter head, (WJN500110), untill you buy a new one remove the plastic bit from the port and see how the pump is behaving without it ... though if the pump is some cheap aftermarket it can be noisy "by default"

The pump was replaced a couple of years ago with a decent quality one. It’s hasn’t been noisy until recently so I’m rather hoping that eliminates it as the problem.

edit. I also replaced a clutch slave cylinder a couple of years ago and then had to replace that one a few months ago. I try not to buy bottom end budget parts, but sometimes it appears that even quality ones can fail.

For anyone interested in the outcome of my problem. I got my local garage to fit the excess fuel pipe that I couldn’t access (as far as I found see without taking the inlet manifold etc off)

The leak was chased town to the injector seals. All replaced and the injector loom replaced (as usual in these matters)

Fuel pump no longer continually screaming but the TD5 seems down on power.

Semper Aliud (translates:there’s always something...)