Attention: TDR Forum Junkies 
A couple of weeks ago I posted a problem concerning a newly installed Isspro EV2 fuel pressure gauge. The issue was that the gauge started "bouncing" over a 6psi range, fairly rapidly. I checked the ground, and rebled the vulcan line that was between the shraeder valve and the gauge sending unit..... Nothing worked. Today I received an answer from Isspro... ... .
Sorry, I have been out of the office and missed that email. Do you have a needle valve before the hose? With VP44 trucks that is necessary to minimize the pulsations from the pump. If you are checking with a mechanical gauge for reference, virtually all mechanical gauges have some damping built in which minimizes these pulses. The electronic sensor is quickly reacting so it picks all of them up (although they will show up on the gauge slower than the actual pulses). We recommend using a needle valve such as ISSPRO R7742, or Weatherhead part 6820 (available at most larger NAPA stores). You install the needle valve between the hose and the fuel system, and tighten it fully then crack it open just enough for the gauge to read.
After receiving this answer I searched again and found that this had been addressed on other Diesel Forums. Thought I would pass this on in case anyone else is experiencing this problem.
Sorry, I have been out of the office and missed that email. Do you have a needle valve before the hose? With VP44 trucks that is necessary to minimize the pulsations from the pump. If you are checking with a mechanical gauge for reference, virtually all mechanical gauges have some damping built in which minimizes these pulses. The electronic sensor is quickly reacting so it picks all of them up (although they will show up on the gauge slower than the actual pulses). We recommend using a needle valve such as ISSPRO R7742, or Weatherhead part 6820 (available at most larger NAPA stores). You install the needle valve between the hose and the fuel system, and tighten it fully then crack it open just enough for the gauge to read.
After receiving this answer I searched again and found that this had been addressed on other Diesel Forums. Thought I would pass this on in case anyone else is experiencing this problem.
