ok so a little update. The issue seems to be somewhat heat related. When it first started happening we had temps over 100 for about a month. It dipped into the 90s for about a week and it got slightly better. Then last week it went back to over 100 and it got way worse. To the point where can't even run at over 2000 rpm on flat ground or it kicks the fuel filter light on. That is a bummer on the freeway with 4.10s.
So i finally had to make some time to really dig into it. Started at 9 tonight
First thing I did was see how much the pump was putting out. Ran a hose into a bucket, and it took about 2:15 to put out half a gallon. that seems really slow to me. The rating on the pump is 140 gph. So doesn't that mean it should be doing about 2.3 gallons a minute?
put my new pump on thinking I had found the problem, it did the same thing
Now I am second guessing myself on if this is a useful test.
So I crawled under the truck and bypassed the FSV thinking that would be the next most likely problem area for a blockage in the line. What a PIA that was. I used 3/8" hose, but it seems like it is too big for the metal lines. Really had to crank down on the clamps. Is there a better size to use? Tried my test again and if anything it was slightly slower out put.
Now I am at a loss as what to do. l thought about buying a bunch of hose and skipping all the hard line from the tank all the way to the pump, but i don't want to just throw money at it blindly.
Oh and i did all the tests with the cap off the tank to rule out vapor lock and it pulling a vacuum on the tank.
Any bright ideas out there?