Yanmar Diesel Engine Question

Story time!

In my 20s, I drove delivery trucks all around northern and eastern Iowa - an early 90s (I think....) GMC Topkick, diesel, 6 speed lo/hi. One day, on a route in Cedar Rapids, I went to leave a stop light and it had absolutely no power. It would idle fine, but when trying to accelerate it would just fall on it's face. I limped it around the corner and into the nearest gas station's parking lot, called the office and they brought another truck, helped me swap my cargo from one truck to the next, then had the GMC towed into the nearest shop. It turned out that their mechanics were just checking the box for the air cleaner when doing the PM. I was shown the air filter and it was collapsed on itself - a new filter was installed and the truck was back in service the next week.

This is related because you said you installed a fuel pressure gauge after the filter and it's reading 0 PSI? How old is the filter? It might not be a bad idea to just install a new one even if it's relatively new - at least you could rule that out as a culprit. Just a suggestion....