I have a cm870 and checking the fuel pressure at idle it jumps from 180 to 280 very fast, cant take a reading. If I rev the rpms to 1500 and hold it there, it will hold steady at 260. Is this normal?
Try a different gauge and see if it does the same thing, could be a faulty gauge. I think 260 is within spec, maybe at the lower end of the spectrum though.
its not the gauge, the whole line is vibrating at idle.
How old are the fuel lines?
2005 volvo and lines are original but not seeing bubles or fluctuation in the davco water separator.
I changed the gear pump with another used one I had and seems to have a 10 to 15 psi more. It stays up at 275psi at 1500rpm. Going to run it this week see how it does.