Almost nothing is totally impossible. The later than your injection pumps apparently develop this issue or can.

The small o ring seal in the lift pump for some reason does not come with the standard rebuilt kit. Not hard to round one up though.
If your thoughts are right just draining a gallon and a half of the base oil mix is not enough. The oil is seriouisly diluted and has to be flushed. I would not drive on it.

Berry, the Mercedes Valve Kit is not a complete rebuild Kit. It does not come with the Little O-ring, Gasket or the large Crush Washer for the Big Plug on the Lift Pump.

The Kits that others sells have all that stuff and often more as the cover other variations of Lift Pumps. The Generic Kits do not have the Glass Filter Bowel that the Boack Kit has.

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84 300D, 82 Volvo 244Gl Diesel

Well sort of have got Me on that. There is what is the most likely normal Cause and then there is some extremely unlikely Causes.

Please note that all Inline Fuel Injection Pumps pass some Fuel Past the Element Barrels and Plungers. If the Pump is OK and the Oil is changed at the proper intervals that is never a problem.

Special Cases:
You have had previously removed the Elements from your Fuel Injection Pump and when you put them back in you messed something up.

You have an M-type Fuel Injection Pump and drip timed it and managed to get the Element miss aligned or did not Torque the Delivery Valve Holder properly.

M or MW type Pump; the Housing is cracked inside.

This is a pic of a 6 Cylinder MW Fuel Injection Pump (This means I am not sure there is an O-ring down there on the Mercedes MW). It shows an O-ring that goes at the bottom of the Element. Pulling even one Element out of an MW Fuel Injection Pump is risky because moving the Element changes the delivered Fuel amount.

The only way I know to check for a leak is to pressurize the Housing and that would also work for a cracked Housing.
While that is best done with the Fuel Injection Pump off of the Engine cracks have been know only to leak when the Item is Hot and functioning.
I have no idea what a good pressure to test at would be other than the Max Pressure that the Overflow Valve is supposed to hold something like 18 psi.

M Type Fuel Injection Pumps don't have that O-rings sealing any part of the Elements. The Element seats directly on the Aluminun Housing on the Bottom end snd the Crush Whasher seals on the top.

If the Element Plungers or the Barrels are scored from passing dirt throuh them or the Fuel Injection Pump has been in use so long that normal wear has worn the Punger and Barrel out they can leak.

Injectors:
A broken Injector Pressure Spring will cause raw Fuel to go into the Engine and it is not going to Atomize. If that happend you should have an obvious miss.

If the Injector Nozzle is worn out some of the Fuel is not going to Atomize well and over a long time it can add Fuel to the Oil. The same if the Pintle tip is burned or broken off.

But, all those are extreme cases that don't occur often and not the first places to look for the problems you have described. Some of the Someone would have had to have done some work on the Fuel Injection Pump and messed up the re-assembly.

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84 300D, 82 Volvo 244Gl Diesel

I ordered the complete kit from eBay with the small o ring in mind. I'm not quite sure what to think though. The fuel primer pump is only two years old But I had the injection pump out of the car for a month while I replaced the head. So maybe the o ring dried up. And maybe it's been leaking for a long time and I've never held oil long enough to tell. I know my dad replaced the o ring under the elements with a step by step play from a local injection pump shop. They told him that if he marked the the elements before he removed them he should have a problem. But I never noticed fuel in my oil until now. Is there a way to check the elements in the car?

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84 300sd 2.47 dif 360k
26 mpg needs lots of love
given to me in pitty

89 civic hatchback auto 140k
33mpgs soon to be low to mid 40's
been in the family since mile 1

85 300d with unknown knock. driven over 30k with knock and still going. sold for $800

I've already pumped the all the old oil out btw. Waiting until I put the rebuilt primer pump in to test if the problem is fixed. Think 40% diesel in your oil will cause long term problems?

__________________
84 300sd 2.47 dif 360k
26 mpg needs lots of love
given to me in pitty

89 civic hatchback auto 140k
33mpgs soon to be low to mid 40's
been in the family since mile 1

85 300d with unknown knock. driven over 30k with knock and still going. sold for $800

No point to worry about that now as it already happend. When everthing is fixed just drive the Car and keep an eye on the Oil Pressre.

If there was some bearing issue there is chance there would be something in the Oil Pan.
I have I think it is 2 posts or threads were I told someone how to mark the Elements MW Fuel Injection Pumps in hopes of getting them back into the same place. However, it was an act of desperation as they had the Upper O-ring leaking.
One of the Threads was about one Month ago.

You Did not say why Dad was pulling the Elements out and did not say if he replaced the Lower Oil Rings or eve if there is lower O-rings.

I have only pulled one Element out of My spare Fuel Injection pump and that was only to write the Post I made on how to mark the pump.
I did not see any O-ring at the bottom but I also was not looking for one.

The Spare IP is buried under a bunch of stuff in the Garage. I need to clean out that area for another project I am working on. When I find the IP I will take a better look inside for the O-ring at the Bottom.

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84 300D, 82 Volvo 244Gl Diesel

This is a blow up of one of the Pics I took when I pulled the Element out of the MW Fuel Injection Pump. Maybe that is an O-ring down there??? I cannot say for sure.

If your IP is leaking from there you will be the first to have that issue that I have read about.

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84 300D, 82 Volvo 244Gl Diesel

Do you know if Your Dad replaced 2 O-rings per element or just the one at the Top. If He did replace O-rings were they one from a Fuel Injection Shop or Gasket Kit or were they ones He picked out from an O-ring Assortment?

I don't know for sure if there is a O-ring at the very bottom see pic.

If I looked it up corrrectly the complete Gasket Kit for the Fuel Injection Pump is $32-$45 plus shipping. I don't think the Governor gasket comes with that but that has noting to do with Fuel leaks.

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84 300D, 82 Volvo 244Gl Diesel

Nothing to be overly concerned about. Rebuild the lift pump and monitor the situation.

At worse if the problem persists a cheap used injection pump would be the logical next step. As long as it is removed from a car with some fuel still in it all should go well if it came to that. .

You could have far worse problems remember. One important thing is not to keep running on thinned out base oil. That can create an issue of more serious magnitude in my opinion.

The oil is the only thing that creates a coating or cushion between metals. Get it thinner and you might lose the protection. Thin enough and you will for sure.

Diesels have serious thrust loadings. Gas engines have much less. You can seemingly maintain oil pressure with thinned out oil but it is not an accurate indicator that enough protection is present. You can use a cheaper dino oil for the current checks. No sense pouring expensive synthetic back in till the issue is known to be solved.

Try to visualize oil density or viscosity as a condom between metals. Take it away and you are screwed.

Without a doubt if continued use where done. Very short term there might be some slight additional hopefully neglishable wear in my opinion.

Us old timers used to discuss diesel base oils well before many members on site where even created. I do not want to see an oil thread.

I have postulated to myself that the reason the 617 does not last longer than it does in general. On the assumption top quality materials where used in construction and I suspect they were.

The average viscosity of the oil we have used was not really adequate to the task. Taking it a bit further running on straight 40 weight or 50 weight during the warmer season might have extended the average 617 engine life substantially. Multigrades claim to protect like a straight 40 for example. They just do not hold the viscosity index as well. My suspicion is even if you had straight kerosene as a base oil. Your oil pressure gauge would still hit the upper stop.

The proof to me is if you have an engine burning oil on say 10-30. Change it to a straight 30 grade and oil consumption will drop in half or more usually. The thicker or more viscosis oil is just not getting past the piston rings as easily.

This is not subjective as I have done this several times to reduce oil consumption. You have to study the multi grade literature. They usually claim it protects like a 30 weight for example but do not really claim it develops the same viscosity. It might for all I know if run as hot as the design paremeters for it where reached temperature wise. I supect they are not in the average engine anyways.

The high viscosity is what you are depending on for engine durability to keep the metals well separated. The lesser the viscosity the more the cushion if you wish is reduced. The oil pump is so powerful in the Mercedes diesels I feel it will not warn you the viscosity is very low. I would even go as far as to say 5-40 in warmer weather might drastically shorten potential engine life.

Easy enough to get data on this one. Who has run a UOA when running thinner oils in the summer? Any indication of bearing metals?

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

I'll ask about the o ring tonight for you. My pump had a lot of discoloration where the element set and that what he went off of. If I remember right the o ring was right below the shims. But I was to worried that he might mess it up to watch. The injection pump guy told us that even the smallest miss alignment Can cUse a miss fire and even not run.

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84 300sd 2.47 dif 360k
26 mpg needs lots of love
given to me in pitty

89 civic hatchback auto 140k
33mpgs soon to be low to mid 40's
been in the family since mile 1

85 300d with unknown knock. driven over 30k with knock and still going. sold for $800

Not really in my opinon as the slow wear in comparison from one viscosity to another is going to be very small in differential. So it would appear to be in the normal range in general by periodic test. Or until the wear is noticeable.

Existing wear undergoes an accelerating period once well established. The only proof would be to put two engines on stands and run them in identical service cycles for a very long time with different viscosities. The average 617 block should probably be capable of close to 500k before needing rebuilt. That's if it is lubricated properly.

It is really hard to find out what they are doing with all the inacurate odometer issues on these cars. I suspect some are making it in an unknown fashion. Some of the examples I have seen have acquired really substantial milage yet the vendors try to pawn them off as 200k mile examples. I have often wondered if they still had the original un rebuilt engine in them. Based this on some of them still seemed decently strong in the engine .In my opinion if the engine had been rebuilt they might have mentioned it but never did.

It was always said in the old days that an equalization of block and head temperatures should be practiced by letting the diesel engine idle for a few minutes before shut down. .Nobody or very few practice this anymore. On the 603 engines it may still be really advisable because of their head issues. I am not suggesting it would eliminate the problem. At the same time it would not hurt either at worse. Repeated hot spots not cooled off to average engine temperatures gradually may crack at some time. The metal thermally fatigues from the stress of the unequal cooling down.

Ill keep that in mind I just demoed the pump and a lot of black thin oil came running out of the fuel pump. Hopeful that my problem

__________________
84 300sd 2.47 dif 360k
26 mpg needs lots of love
given to me in pitty

89 civic hatchback auto 140k
33mpgs soon to be low to mid 40's
been in the family since mile 1

85 300d with unknown knock. driven over 30k with knock and still going. sold for $800

Wel I replaced the I ring. Drove it around put can really tell. I'm going to hit the interstate to see if she doesn't gain oil. But my oil is leaking again

__________________
84 300sd 2.47 dif 360k
26 mpg needs lots of love
given to me in pitty

89 civic hatchback auto 140k
33mpgs soon to be low to mid 40's
been in the family since mile 1

85 300d with unknown knock. driven over 30k with knock and still going. sold for $800