Hope it solved the problem. Just incase. I found the thread I was speaking of.
This is for maclaveau

I believe the IP has to be removed to scribe it accurately.

If someone has to do this don't loosen anything till you have scribed a make across the Element Flange, Shim, and the aluminum Housing. Remove only one Element at a time and replace on only one at a time.

I never looked closely inside after the Element was pulled to see if there is another O-ring down their to seal at the bottom.

There is a spacer that goes on the upper portion of the Element and it will push down on the Upper O-ring. I think in some cases that spacer can rust out.

If you have compressed Air before you loosen anything blow out the area under the Element Flanges.

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84 300D, 82 Volvo 244Gl Diesel

Which year and model diesels use an MW Injection Pump?

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'81 300SD

All.....Only euro spec cars came with a type M pump...You can tell because the shut off is ontop of the injection pump....no ADA, ALDA or EGR....

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I am not sure on the 300Ds but 240Ds depending on the year and maybe some other factors can have M or MW type Fuel Injection Pumps

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84 300D, 82 Volvo 244Gl Diesel

That's interesting because I would expect 617 engines to have the same issues with degraded o-rings that the 603 and 606 engines have, especially when using biodiesel. I thought that one of the reasons 617s could run on just about anything was because there are no rubber seals in the IP's fuel delivery channels.

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'81 300SD

The O-rings on the Delivery Valve Holders of the M Type Fuel Injection Pumps are exposed to more heat and high pressure then below and the pulsations/shockwave in that area are more violent.
As you said the M types don't have an O-ring in that area so they are immune from that paticular issue.

The O-rings on the Elements of the MW type Fuel Injection Pumps are only exposed to the pressure controled by the Fuel Pressure Relief/Overflow Valve and the pulsation. The max pressure on mine in the Manual is only 18 psi and that at high rpms.

Also cool Fuel is going in and hotter Fuel going out so the overall temp is much lower than in the Delivery Valve area.

Also the O-rings are of a wider crossection.

I think at some point in time you are going to more frequently see the MW pumps leaking around the Elements. But, what is happening is the bulk of Cars are being eliminated before that happens by accidents or other mechanical failures.
Mine seems to have survived being overheatd due to a leaking Water Pump and my wife stopping but still contiuned to drive the Car after it had cooled down. So mine just missed going to the junk yard.

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84 300D, 82 Volvo 244Gl Diesel

I think that the point in time you speak of is occurring right now with my IP. The leak came back to the point where it's leaving a small puddle under the car. I've tried tweaking a few things including an extra little torque on the delivery valve, but the pump is still leaking a small amount of fuel from underneath the shim on the second delivery valve.

Any ideas how much it would cost a diesel injection shop to replace the o-rings mentioned earlier in the thread? I'm kind of leery about pulling an IP from the junk yard.

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'81 300SD