IF/WHEN you replace the glow plugs is a good time to do a compression test. If it starts and runs fine, don't look for trouble.
My self? The first thing I check on an unknown engine is valve adjustment and compression but that is just me. I want to know what I am dealing with and I also have all the equipment required. It's no big thing for me to pull the injectors, pop test them, replace the heat shields and install new fuel return lines.
I suggest running a good cetane booster with every tank of fuel. These old diesels perform better with a little extra bit of "oomph" to compensate for the ULSDF we get at the pumps.
I use the Stanadyne brand but there are many others available.
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