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Hello and here we go again Lol! Well first I'm not sure if this is the best spot to put this thread if it's not please Moderator's move it to where it shoud be. Now to the problem at hand! I have a 69 Pontiac Firebird that I have mofied the tank and installed a welded in sump from Jegs. I simply used a hole saw and popped a bunch of holes of the appropriate size (I forget the specifics) Anyway I washed the tank out and welded the sump in washed out again presure tested and repaired as needed and washed again. I ran a 1/2 aluminum line along the frame rail changed to 8An line to a Holley regulator and on the 850 DP Holley. At the tank I installed a 3/8 inch vent line at the top of filler neck {and yes this is clear} I used a 90 out of theb tank to 8 an line on to a Fram canister filter that goes to a mallory Pump that is fixed at 6.5 psi. The filter and pump are hung off of the hanging strap bolts and are tied into the 1/2 inch line with 8an braided. Now the issue that I am haveing is that as the pump run's the Gauge slowley goe's down? It goes dow'n to the pointb that I feel that it might be an issue at some point or another while cruising. The gauge is newer and of good quility the pump is brand new and was swapped for a Holly Black which I now believe to have been good but swapped for the new Mallory. Guy's what the heck is going on here? anyone have this issue?? The tank is clean the lines are all nice and large enough to provide plenty of fuel to feed a lot of Hp. I am about to yank the tank again but really don't want to unless I have to. Once again sorry for the very long discription but I hope I am clear on whats up...

Any idea's
 

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Could be an insufficient ground at the pump/tank etc. As the pump pressures up, the current demand rises,with a weak ground, the heavy draw can load the ground circuit and cause the resistance in the gauge circuit to change , causing a "floating " reading. Not sure if that is your problem here, just thinking out loud I guess. :D
 

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I have had 2 different fuel pressure gauges on my hot rod that do the same thing. The only one that reads right is an NOS gauge I'm using as a back up. Try disconnecting the fuel line and see if you have fuel coming out. I bet it's just a gauge issue.

Keith
 
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