Listing truck details in your signature line helps us help you so we can read it with each post as needed.
If you can post a couple pics of your ffm- that will help identify which one you have and be sure we tell you which is which.
The water in fuel sensor is the 3 wire part on the side. The drain is NORMALLY the one next to it. If you look closely at that side you should be able to find the word drain there. There were a few different versions of the ffm over the years, and thr hummer one is slightly different with a 90° Bend in it’s fitting, (pics below) but they still have it in same location afaik. Diesel fuel on an old toothbrush is usually best way to clean out junk built up around the words to read them.
Your db injection pump (db0,2,or 4) can be read on name plate of it. The input line is in the rear, middle of the 8 hard injection lines. Factory for gm is 5/16, but on ford and most all equipment is 3/8. 3/8 is better and a good upgrade to do, requires 3/8 output modified from ffm obviously. The return from the ip (injection pump) is 1/4” and about 5” long, It is good practice to replace this with clear tubing to identify air intrusion contamination of fuel, verify fuel flow, etc. There is fuel rated clear, but most folks just get the cheap stuff at a hardware store and replace it every few years because it’s so easy to reach and so cheap.
I always suggest putting in a hard “Tee” at the ip inlet and attach a fuel gauge there which can be read while driving. Low fuel pressure destroys ip. Bad lift pumps make the same sound as good ones. Your db pump if not a hortrod modified pump should max at 5psi. From 5-8 psi it will advance the engine timing. Above 8 it will create real problems.
