I recently purchased a '92 300D with the 2.5 turbo. Great car! On pre-purchase inspection the seller had a shop check compression and fuel injection pump pressure, removing the number one fuel injector. It has been leaking between the injector body and injector where the two screw together. I've removed, re-tightened, no luck. Is this a sign the injector has gone bad?

Also, now that I can see the whole area, I notice small bubbles between the prechamber and the head where a small amount of fuel has accumulated, suggesting that the seal between the two is not up to snuff. The engine has 140K on it--can this be remedied by buying a splined socket to tighten the prechamber nut? Or, is this a sign of something more? Anybody haev any experience with these demons?

Hello beartooth
1992 300D with the 2.5 turbo.
#1. The injector can be rebuilt or replaced.
Vehicle 1992 Mercedes Benz 300D Turbo 2.5
Part: Diesel Injector
Note: Bosch 0.432.217.169
D1000-39655 Diesel Injector Bosch IN STOCK $67.37
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1HJ1E3CVZ1HJ1E44CM&year=1992&make=MB&model=300-DT-003&category=D&part=Diesel+Injector

#2. The small bubbles between the prechamber and the head is a cylinder compression leak, the PPI garage may not have replaced the injector heat shield after compression test.

You are not clear, did the PPI check only one cylinder for compression?

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Roger on the injector. Dissabembled it again yesterday, cleaned all surfaces, and re-installed. Still leaks. Ordered a replacement.

Also, I ordered a splined socket (PP4Benz) to see if tightening the precahmber nut would resolve the compression issue. As best I can tell, only the first cylinder was checked for compression. Without knowing what the results were beyond "OK" and without knowing what the other 4 cylinders showed, I can't of course, say if overall compression is good. I'm hoping that I don't have a head gasket or head problem, and am thinking I will just keep an eye on this for the moment. Any thoughts or experience with this one?

Injector pump pressures were between 320 and 340 PSI, which I undertand is fine--minimum is suppoed to be around 270.