So long story short, I've been having issues with my new FASS (the thread right beneath this one). I've called FASS twice and they've been great both times. However, the new diagnostic measure they want me to take is to use a rag and vice-grips to clamp off the return line at the VP44, and drive it around the block.... Has anyone else done this?? I know they are some experienced people, but with their not being a return line, I'm worried this may damage the diaphram in the VP44 if the pressure gets too high. Will the FASS regulate the pressure beneath dangerous pressure levels with the VP44 return line being clamped off? The point of this test is to see if the overflow valve is stuck open.

 

It very unlikely that there would be enough pressure developed to cause damage to the IP diaphragm (30+ psi). I know a few guys who are running in the 25 + psi range routinely. Do you have a fuel pressure gauge on the truck? That being said its not to tough to simply take the return valve out and have a look. If you can find a regulator with a gauge for your air supply put some air through it and see if its opening and closing. There is a bleed hole so some small amount of air going through the bleeder is normal before it actually opens. Its just to help cool the pump for the lame low pressure stock set up.