My IP only has about 80K on it and I don't think I would reuse it, it's too much of a PITA to R&R. I guess you could save up to $1000 if the head didn't need much, probably doesn't make sense for those of us with 400K mile heads.

If you're replacing the short block..........R&R of the IP is easy...........the engine is in the garage.

I was thinking about the next time the IP needs to be replaced, I would rather have a fresh one.

Well, you're a special case: longevity desired: forever.

I'm curious as to how well an IP with 300K on the clock performs as compared to an overhauled unit........and what the longevity will be for each of them.

It's probably a rhetorical question.

That is a good question. In my case, the reman IP made my engine run smoother than it ever had since I bought it (with about 150K miles). I just don't see the point of putting a high mileage IP on a fresh engine, the performance probably wouldn't be optimum.

I do suspect that a lot of the shaky/smoky issues on high mileage engine are (at least partially) IP problems. Even though they rarely "fail," I do think the degrade and affect performance.

Has to be the case.

With no seals in the IP, you cannot expect the same delivery pressures after 300K miles. Nothing mechanical can run without any wear.

Yup, that's a lot of cycles with metal to metal contact. I don't know any real way of testing them for pressure/capacity and if you're going to open them up for inspection you might as well rebuild them. I guess it's just one of those things that is reasonable to replace after 300K miles, or so (timing chain, oil pump, oil pump chain, etc.). At least they don't do any real engine damage when they finally do fail.

It depends on how much of the IP they replace. When I did this sort of work back in the 70s gaskets/seals, tappet pins, pin bushings, cam rollers and bearings were always replaced. After that it depended on what was worn out.
The plunger and barrels were inspected for scoring; if not obviously scored the old ones were put back into the pump.
The pump is hooked up to the test stand and enough adjustments are done to the pump so that the pump can be run up to temp. Ounce the pump is at operating temp. the pump is run slow to simulate starting. If the plunger and barrels do not pass the "Starting Quantity Test" the pump is opened up again and new plungers and barrels are installed and the calibration of the pump starts over again.
Normally you can see of the plungers and barrels are bad and replace them. Rarely but ounce in awhile a well maintained pump with a lot of hours comes in and the plungers and barrels look good but are worn out and you will not know till the Starting Quantity Test is done.
While a lot of the old parts are reused in the rebuild there is still the benefit of each fuel element being brought back to spec. as to being timed to the IP camshaft , the Governor settings, and of course fuel quantity.

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84 300D, 82 Volvo 244Gl Diesel

Can you describe paremeters of the start up test on the plungers and barrels? Also if you are static timing a pump just with gravity feed fuel oil on a car. If you reach your normal shutoff point but the element continues to leak as you go by it at say a drip a second. Is that that plunger and cylinder still considered serviceable?
I personally would think not. If it leaks that bad with virtually no pressure what is going to happen when expected to work at normal operating pressures? A partial flood past the piston? Also I would think it might indicate some other bores or pistons in the injection pump could be even more worn. Less worn is a possibility as well i guess.
How is this going to affect milage as well if you have this kind of wear. One last question since I am a little on a roll here with a guy who has worked proffesionally on piston injection pumps. It seem reasonable to me that a pump internally leaking in this fashion also would even have more difficulty if it was hot. Therefore making hot starts even harder or impossible.
Any comments welcome as we very seldom if ever have the presence of an individual that has worked on the pumps at sometime or another.
Please also excuse what I would think are pretty elementary questions to you. The urge to know the answers is strong though perhaps by many on this site as well as myself. Sorry about the semi hijack of this thread as well.
Metric rebuilders just might know where there is a recent rebuilt engine of theirs with very little time in a car that is either for sale, smashed or whatever. This may be worth talking to them about as well.
The engine warranty might even be transferable. Butter them up with I would not like to see an engine that I had rebuilt go to waste either if possible. Chances are nobody else may have taken this approach . Whats there to lose?
Also dropped diesel 911 a private message to please drop back here if he has a little time. His past experience, knowledge and hopefully advise are more than welcome. Just thought he may not normally cruise down this thread again. We cannot risk him being the one that got away as well at this point.

X2.

Can you describe parameters of the start up test on the plungers and barrels?-- I was describing what was done when the pump is on the test stand inside of the shop not on the car. The idea of the test is to duplicate what the fuel output during a hot start. I do not know the specific spec. on these particular pumps but the pump is run from 300-350 rpm (also there is a set of calibrated test injectors hooked up the pump with the hard lines). You hit the button and the machine gathers 1000 strokes of fuel output from each of the pump elements into graduated measuring tubes. You compare that amount of fuel to the spec. sheet. If it is not putting out enough fuel the plunger and barrels in the pump are worn out (and if the pump was on a car after it gets hot the car may have trouble starting).
So the fuel either goes out to the injectors or it squeezes by the plunger and barrels; when the pump and the fuel is hot more of it squeezes by the plunger and barrel.
Also if you are static timing a pump just with gravity feed fuel oil on a car. If you reach your normal shutoff point but the element continues to leak as you go by it at say a drip a second. Is that that plunger and cylinder still considered serviceable?- The static pump timing (also called I believe the Drip Method) is used to check the start of delivery of the fuel that would be going into the injector. If you have reached the degree mark on the engine damper (as per the Manual) and you are getting more drops per minute the Manual tells you the injection pump timing is not correct and you need to rotate (advance) the IP until it meets the manuals specs. Not much of the above has anything to do with fuel leaking past the Plunger and Barrel (due to wear) as the gravity feed pressure is not enough to effect it.
The 2nd paragraph starting with -I personally would think not. And Ending with--Therefore making hot starts even harder or impossible.---Again gravity feed pressure used on the static timing has nothing do with the worn plungers. If the Plunger and Barrels are worn enough and enough fuel is leaking past them less fuel gets to the injectors and makes it hard to start the car when the engine and fuel system are hot. When the fuel is hot it is thinner and more easily flows through the clearances.
If you have an IP that has an extremely large amount of miles on it, or you know that water (especially if it sat inside IP for several days), or dirty/contaminated fuel got inside the IP, you have eliminated all of the other less expensive causes, and having hard or no start when the engine and fuel system is hot you might begin to suspect the IP as the problem.

I am not familiar with Metric Motors but all rebuilder are looking for good cores to rebuild with.

The main point of my origional post was that when an IP is rebuilt the pump will be calibrated to the origional/or updates specs. but Plungers and Barrels are reused unless they are no good.
If you want the Plungers and Barrels replaced you need to ask them to replace them (the cost will go up) and make sure they do not give you and exchange pump. It is also a good idea to tell them that you want the old parts saved and given back to you. It is also a good idea to get an itamized list of parts replaced; an invoice with something like "pump rebuilt $1,000" and nothing else dose not tell you much.

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84 300D, 82 Volvo 244Gl Diesel