1985 Mercedes 300d IP dead?
 

So, my mercedes has recently stopped starting. It started off just being very difficult to start, lots of white smoke, me having to prime the hell out of it and eventually getting it started. Then it completely stopped working for me.
so... I changed the fuel filters and realized the glow plugs were mostly bad, so I replaced them. I also have fairly new fuel lines. I've bled all the air out of the lines and I also have a new primer hand pump.
After bleeding the air out I was able to get the car started and drive it again for about a day.
Then it stopped starting again.
While trying to bleeding the air out of the lines again I noticed I wasn't getting any fuel from the front two injector lines.
So I cracked them at the pump and noticed I wasn't getting fuel there either. I'm getting fuel into and out of the lift pump as well as from the secondary filter into the IP.
So... is my IP toast?

As I said, I've replaced the lines and bled all the air out. When I loosen then banjo bolt for the line coming out of the secondary there are no more bubbles coming out, only clear golden fuel. When I crack the line going into the IP right at the IP fuel is coming out just fine. So I'm getting airless fuel just fine into the IP. I can crack the back three lines and I get fuel but just not on the front two.
It's possible that some contamination could have been in the fuel before I cleaned everything up though. Would this have damaged my IP? Is there a way to flush it without being able to start my car?

thanks,
I think this may be a bit beyond my present skill level.
I'm afraid of screwing something up.
I've already read some horror stories of people screwing up their IP by messing with the delivery valves.