Hi all, I am a new member here. I have been using peachparts as a resource for a while, but I am totally stuck. So, I'll get straight to the problem (in short), and if you are curious, I'll put all the gory details after it

The Problem (semi-short): 1985 300TD Wagon will not start. After reading about a lot of problems here, I am pretty sure I have isolated the issue to the IP. I would like more knowledgeable members to either confirm my diagnosis and tell me where I should go from here, or explain to me what I am missing. In short, I have hooked up a small diesel fuel supple to right before the hand primer pump. I have also recently replaced the line from the spin on fuel filter to the IP with a clear line to help in diagnosing. I have removed the five hard lines which run from the IP to the injectors. After priming with the hand primer, I cranked the engine for 10 seconds and nothing came out of the IP. I tried priming again, cranked, and repeated for a total of 3 or 4 times. Nothing came out of the IP. I think this is an indication my IP has an issue. Am I right? How do I go about fixing this?

The Problem (all the gory details/long): Here are some more details that may be relevant about the car. My brother and I recently got this 1985 300TD wagon. He has had a 1982 we have worked on a lot (and spent a lot of time in). I am OK at working on cars, and I love it, but I do lack some knowledge (but I am trying to learn). The 1985 that is having problems was purchased a few months ago. At the time, it was not running. It has a dual tank system for running WVO. The car has 472,xxx miles on it, and we got it as a project for a good price. After having it for a few days, we hooked up a good diesel supply (in the way I described) and were able to get it to run off of this. It was rough to start, but once we got it running, it ran fine. On subsequent starts, it started normally. We then began the process of cleaning all the lines and the tank for the smaller of the 2 tanks which is intended to be run with diesel. We replaced the inline filter (for that tank) and the spin on filter. We primed the lines and it ran fine on this tank (although it did die two or three times early on, but I assumed it might just be air in the lines or something). In short time, the car was running great on the small tank. Then, we began cleaning the second tank and its lines. After this, the car was able to run on either tank successfully. One day, while running on the larger tank, the car died. I think I had run this tank dry (apparently that gauge is broken). I took off the spin off filter and the diesel in it seemed a little odd (possibly minimal water contamination or something), so I dumped it and refilled it. I switched over to the smaller tank and was able to get it running again with some coaxing. After all this, it ran great on this smaller tank. I assumed that the car's death was due to the large tank running out. It was running so well on the small tank that I went ahead and insured and registered the car (a little over a week ago). When I took the car on its maiden street voyage (I have been driving it only on my property up until this point) it died about .5 miles from my house. I pulled over and hooked up a clean diesel source right before the hand primer pump. I primed and was able to get the car running. I got home it struggled and died. I then primed again and it started up. I hooked everything up to the small tank again it it seemed fine. I tried to drive it up my street and it died. I rolled it onto my property and cracked one of the lines at the injectors and cranked. Nothing came out. I loosened it more. Nothing came out. I took it totally off on the injector side. Nothing came out. This is when I got worried. I thought the IP might be clogged. So I blew some compressed air into the IP. I tried cranking again. Still nothing. So then, I made the set up I described above (with the clear line and all 5 hard lines removed). I just tested this today, and nothing comes out of any of them at all.

Bottom Line: Is my IP busted? Where do I go from here? Any ideas are greatly appreciated.

More about me, the car, the whole situation: I love these old MBs, but I know I don't know everything. I try to research everything online before posting (hence this is my first post). Sorry if this is really wrong but I am very stumped and a bit frustrated, but any ideas will be very appreciated. If anyone needs any more information, I tried to be thorough, but please let me know. Help me help you help me by telling me if I am missing key details. The car was run quite a bit on WVO by previous owners, but I have not used any in it ever. I have heard IP problems are hard to fix sometimes and are often misdiagnosed, so I want knowledgeable people's opinions on how I should proceed. I got the car fairly cheap, but I don't know a whole lot about if it, so I don't want to spend too much money on it unless people think it will be reliable. If I posted in the wrong place or something, please let me know, I'm new!

Much much thanks,
Kevin