Yes, the seals are under the fitting that the injection line screws too -- I think the are under the actual valve in yours, so you will have to take out the spring, valve, and valve holder. The seal is the little copper washer underneath. Put on new 0-rings, too.

If you had dirt in the pressure valves, I'd guess you managed to get dirt past the filters (very bad sign-- unless it is varnish from crappy fuel, in which case a good blast of Diesel Purge or several treatments with RedLine or similar should take car of it). Very much grit in there will kill the IP for sure.

I believe opening pressure is in the 1700 psi range, but I've been wrong before.

Certainly, if you have an injection tester, pull the injectors and at least check them for spray pattern. It should be a fine mist, conical, and even around the pintle. Any unevenness, sputters, drips, or solid stream will indicate a bad nozzle ($50 or so each on FastLane). You should also be able to get the nozzle to "buzz" and it opens and closes with slow application of pressure. I think it takes some practice to get them to do that, but it shows that the nozzles are working properly.

Any crud in the nozzles with give bad spray patterns, high or low opening pressure (depending upon whether they are stuck open or closed!), and intermittant operation.

Chain stretch of 8 degrees or more indicates replacement is needed. More than that, and you risk serious trouble, usually a broken chain.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!