My truck just started stalling between shifts and is holding extremely wierd rail pressure. At idle its holding between upper 3k and low 4k for pressure when it usually ran between 4800-5100. I have an air dog and just recently changed filters, I also installed a new FCA about three months ago. Im thinking it could be the fuel pressure relief valve but im not so sure on what the proper way to test it is.

 

when the truck sits for about 30 minutes and you start it up the rail pressure spikes up to 20k and idles rough! any ideas fellas?

 

Remove the MP-8 and see if the issue still persist.

MikeyB