Are you 100% sure that all of your lines are smooth bends and no kinks in the soft or hard lines?

Are you 100% sure that your fuel sender/pickup foot/pickup tube is not sitting on the bottom of the tank restricting fuel flow when more is being demanded?

Are you 100% sure the slots in the stand pipe are lined up properly in the fuel filter bowl?

Did you replace your fuel pump or was that someone else recently that had to?

 

thanks for responding sous, started to think everyone gave up on me. i'm not 100% on the pick up foot but pretty sure its not touching the bottom. My measurements on the foot seemed correct and i have a metal tank so it doesn't have the flex that the plastic does.
as far as kinks go the soft lines defiantly don't have kinks and i really haven't touched the hard lines. anything is possible at this point.

im not sure what you mean by slots on stand pipe lined up properly. are you referring to the "tower" or check valve in the middle of the filter bowl? I had no idea there were slots that had to be lined up. I would do ten back flips if that is the problem as ive spent so many hours trying to track this down. I don't remember guzzles instructions mentioning that. will look that up now.
just an update on what i did today. bought another fuel line aand ran it from the pump to bowl only to find out i can't get the threaded fitting on the fuel bowl without removing or cutting the inlet line out of the way. i didn't want to do that quite yet. i blasted some air back through the inlet line towards the pump while it was disconnected. also put air through the return line while disconnected . I then hooked the inlet line from pump back up. ran the truck no change. then i put a 5 gallon jug of diesel in my underbody tool box and ran the fuel line from 5 gallon jug to the pump. ran it around the block and the fuel gauge was all over the place. parked in driveway to find diesel dripping all over the driveway. I guess the return line pressurized the tank and existing fuel line that was still connected to the truck fuel tank and leaked everywhere even though i plugged it with a pen. Does that seem right?? does that mean i have a vent plugged somewhere on the tank?
Also was thinking that maybe the compression fitting in the tank on the 3/8 line could have been to tight and compressed the brass ferule to much, which could have kinked / collapsed the metal fuel line???? Almost like i have to redo the whole hutch mod again( new compression fitting) and run all new fuel lines from tank all the way to the filter bowl. Reeeeeeaaaally don't want to do everything over anyone with any input , guesses , crazy thoughts, anything.... would be greatly appreciated. This is definately a odd ball fluke and probably something super simple

 

We are not giving up on you friend, most are probably out of ideas though and it is difficult to troubleshoot over a forum.

The stand pipe is the black plastic pipe in the middle of the filter housing with the spring valve in it. There are slots on both the inner and outer pipes that should be lined up. Baatzy had this problem a year or so ago and his low FP was due to the stand-pipe being out of alignment.

The return line should not have pressurized the tank. I am not familiar with the steel tank, but I would assume there is still a vent or two of some sort.

 

well I pulled the sending unit out and re measured to the bottom of the tank, looks like I have a half inch between the bottom of the tank and the pickup. I also double-checked the compression fitting to see if the pipe was squished and it was okay. The only thing I found was this little indention on the inlet line right before it goes into the fuel bowl. It almost looks like it was that way from the factory but I was just wondering if any of you guys have the same crimp Mark on yours. You guys think that that little crimp could cause my fuel pressure drop? This crimp Mark is on the inlet line right in front of the fpr. It runs vertically

 

Jason, I've been thinking about this, which side of the fuel bowl do you have your pressure sending unit pre or post?

 

Hard to say for sure but I doubt that that crimp would cause a problem. Also, you say it's near the FPR, the FPR is in the return line. When the fuel pressure reaches it's max the spring compresses and lets fuel out to the tank through the return line. (If my understanding is correct)

 

yes sir, i was just stating it is by the fpr to give an idea of location.you can see the frp screw behind the fuel line in the picture above. the crimp is on the inlet line though. whenever one of you guys get a minute, if you could take a look at your inlet line and see if you have a crimp? not sure if its just mine. i have eliminated just about ever other possibility and still stumped. its driving me crazy. fuel volume is the real problem here, the pressure is there it just doesn't have supply for the demand when i give over half throttle. So if the 5/16 line is crimped down to say 1/8 inch line, i could kinda see the restriction which would in turn give less volume. problem is i cant run another line until i bend the hard line out of the way in order to get a barbed fitting into the bowl. i guess i could just replace the hard line if that ends up being it.

 

sender is post filter and the filter is brand new

 

Ok, any reason to think your fuel pressure sensor is bad? Anything besides the drop to make you think this? If you didn't have the gauge could you tell there is a pressure loss?

 

Were you able to verify the stand pipe slots in the fuel bowl were lined up properly?

 

These two things seem to make the most sense. I would be checking that stand pipe since it has happened before. I would also wonder if you would be able to tell if you didn't have a gauge. Mine drops about 5-7 under a pretty hard pull when towing, but yours may be normal as well.

 

the fuel sender and gauge are brand new. I don't feel a huge difference in power when it drops but it's only dropping down to about 50 PSI from 65 PSI. I'm just wondering how much more power it would have if it didn't drop that far

 

Is your gauge digital or analog? Is this drop only when you're hammering it, towing, or gently taking off from a stop light?

 

sorry sous , I forgot to mention that I did that yesterday as well. I tried to line up the slots the best I could. It seems like the standpipe would go in no matter which way it was positioned like the slots wouldn't go down into the grooves of the bowl. I also checked the check valve by pushing down on the center of the standpipe . and it seem to be working properly. Should I take all the guts out of the check valve and try running it like that?

 

it has the electric sending unit to a analog gauge, autometer ES. The pressure will drop even at a quarter throttle but it only drops 1 or 2 PSI. The more I go down on the throttle the more the pressure drops. The pressure does go back up slightly at each gear change