when we remove the secondary fuel filter on our c15 the filter has pressure in it and it sprays fuel everywhere. what could be causing this issue?
That filter is on the pressure side of the fuel system but with the truck shut off for more than a minute pressure should drop to nothing in that filter.
Most likely cause would be some type of blockage in the fuel return line from the back of the cylinder head, or a stuck closed fuel return check valve.
we changed out the return line from the back of the head ran the engine and let it sit for 5 minutes we still had pressure in the filter. so we changed out the return check valve ran the same test and the filter was still pressurized. removed the return line from the filter housing and put a test line on and had the same results.