Hi guys!

I've been lurking the boards for a little while, and a couple of weeks ago I became the proud owner of a straight, clean, and rust-free '82 300d with 306k on the clock. I've been working my way through the preventative maintenance, so please forgive me for the number of questions I'm about to ask! I just had the valves adjusted and compression checked. The compression came back at 250 +/- 5 across the board. Since there is minimal blow-by and nothing visible coming out of the exhaust, could this indicate gummed up piston rings which need to be cleaned? If so, what's a good way to go about that?

Also, the shop said they noticed a rattling noise coming from the chain tensioner area. They said "it wasn't building pressure like it's supposed to", and recommended replacing it and the timing chain altogether. I'm all for keeping this car on the road, but I'd really rather confirm for myself what the issue is and hopefully fix it myself rather than just throw money at it. Is there a way to diagnose a chain tensioner which is going bad, and is there a less expensive fix than just replacing everything? I'm not shy about doing my own maintenance, but I also am new to diesel engines.

Thanks in advance!