Wow. Ten pages in this thread. I admit, I limited myself to 30 minutes, so I skimmed.
Wayne has been very helpful reminding me when the forum server has gone to sleep, and he asked me to weigh in on this thread.
Fuel delivery issues. Gawd, how many times have I been down this path.
1) Pre-filter. It's been mentioned upthread but bears repeating: A PAPER PRE-FILTER CANNOT BE USED ON A DIESEL. They all lack enough surface area to flow enough fuel with diesel's viscosity. You may as well read my
Tale of Woe on my own experience accidentally substituting a gas paper fuel filter for the OEM Nissan wire mesh filter.
2) Gasoline-to-diesel conversions: gasoline vehicles have internally galvanized fuel tanks, and diesel vehicles' tanks aren't. Diesel (and biodiesel) will "eat" the zinc and the zinc migrates to the filters. Fast plugging? You bet.
3) Fuel quality. The pics of your fuel in clear containers makes the fuel look awful. If
anything more than a tablespoon (liquid) or one-half teaspoon (solids) settles out, it should be separated and filtered (cheesecloth-type method) before reusing, or sent to hazmat (or used for bonfire).
I had contaminated biodiesel that had floating crap so bad that I had to pull the tank on my '81 720 to adequately clean it. NO WAY could I get it all cleaned out without taking it off, removing the sending unit, and really spraying it out over and over with cleaning agents. That was my first Nissan diesel PU. This link with pics appears to be dead, but I'll post it anyway:
http://biodieselnow.com/forums/p/6669/48513.aspx .
Here's a picture, looking into a 260 gallon tote through a 6" fill hole.
4) See this collection of my "
Al's Fuel Systems Problems Greatest Hits, Vol. II". Read it, it won't take ten minutes.
5) Tank pickup restriction. Read
gromit's tale. This kind of thing is more common than you think -- I've fought it at least four times over my careers.
6) Diagnosing fuel delivery problems. Quoting myself:
"For fuel delivery problems, I use the same method most every time. I teed into the pressure line off the fuel pump, got out my old Sears vacuum/pressure gauge (it was old then; it's positively ancient today) and duct-taped it to the windscreen, connected it to the tee. Drove the truck. This time, I could see the fuel pressure falling off long before the truck began losing power. OK, fuel delivery problem confirmed."
Use the vacuum/pressure gauge, a tee, and some clear fuel line. Paste the gauge to the windscreen, and if you can make enough gap at the hood, also bring the clear fuel line up so a loop of it can be seen through the windscreen. Tee at the firewall or the fuel pump, not any further back. You need to know what's happening at the engine.
The vacuum/pressure gauge will tell all.
First, tee between the firewall hard line (from the rear/tank) to your prefilter. Run until you have a symptom/missing/loss of power. What does the gauge say? More than 1" vacuum? The restriction is somewhere between the firewall and the ass end. I've had crushed lines, rusted lines, lines filled with crap in the fuel, water (harder to pump that fuel), plugged vent line, rusted pickup tubes and probably others I'm forgetting.
No big vacuum on that test, but still loss of power? Move the gauge's test tee to the pressure side of the fuel lift pump. Repeat test drive.
Fuel pressure started high but dropped down under load or after a while? You've narrowed the problem to between the firewall and the fuel pump. I've seen plugged filter(s), collapsing inlet lines, and failed check valves in the fuel pump. Also, one defective filter head, I can't recall the details now.
Fuel pressure was good and stayed good, but still loss of power? Move the test tee to the line feeding fuel to the IP, repeat test.
Fuel pressure dropping when loss of power? Look hard at that secondary filter assy. (element, head, internal check valve AKA overflow valve).
Fuel pressure OK idle + under load? Has to be the IP or engine hard parts: you do not have a fuel delivery problem (delivery to the IP, that is). That said, the Inline IP is about the most robust part on a SDxx engine, so I would not condemn it lightly. Other than the leather diaphragm, they're as close to indestructible as an IP can be in consumer automotive-land, IMO.
I own (and sometimes even drive) a 1999 MB E300 (OM606.962 turbodiesel) these days, and it's infamous for air leaks (and fuel leaks) on the low-pressure (vacuum) side of the fuel system. I kid you not, there are
SIX molded hard plastic fuel lines on the feed side, each with two o-rings to fail, four more o-rings on the main filter head, an electric
shut-off valve with one obvious and two well-hidden o-rings, and a raft of other rubber lines and connections all waiting to prevent you from starting if the car's nose isn't pointed downhill, or if you have less than 1/4 tank of fuel. And they'll leak fuel, too, trying to ruin the large underbelly covers.
Air intrusion into the E300's fuel system is a fact of life. Oh, yes, I'm familiar with air getting in the system. Two words: clear tubing. You can use the cheap aquarium-quality stuff for a short test, as long as you are careful not to route it near hot things and not to let it abrade. Hood off, or careful routing out the grille, and you can run down the highway with 15' of the stuff plumbed in. You can see the stream of little bubbles as the fuel passes in front of your eyes on the windshield.
I suspect restriction(s) rather than air, but both fit your symptoms.
Other random thoughts:
EGT probe: useless unless it's
pre-turbo. EGT readings taken post-turbo are generally regarded as useless.
Change the coolant! Do it now! Don't worry about the cause unless it continues to turn color quickly. If you're not blowing the radiator cap pressure limit while driving under load, and there's no oily sheen in the coolant reservoir, chances are good the HG is OK. But there's crap circulating in the coolant from somewhere, and it needs to be let out. Flush the system as best you can. If you have a working heater, disconnect the hoses to the heater core and use a garden hose to flush in both directions, lots of water. The heater core is the de-facto filter for the cooling system. If you've ever hand-flushed a heater core when it's outside the vehicle (ie holding it in your hands) and shook it and flushed, shake and flush, you know what I mean: more crap comes out than you can believe can fit in that core.
You don't have to remove the core to do a half-decent job of removing the loosest crap, but do try to flush it when you're changing out the coolant.
8pm is coming, and that's my bedtime folks (I get up at 0330 these days, for commute to work), so that's all for now. Get out the old vacuum/pressure gauge, buy a plastic tee or fab one out of brass fittings, buy a bunch of clear fuel line, and get testing. It's easier to find the problem than you think.