I've got 5.5 on start up. Then drops to 2.5 after a few minutes. I briefly checked the lines and looked decent. Tomorrow I'll have more time to look at the rest. Any other ideas? Thanks

mechanical or electric pump ?
do you use an adjustable regulator ?
are you running a return line from the pump ?

Mechanical pump, no reg. No return line. Even changed out pumps.

Try loosening the gas cap, vent may be plugged.

(1) The gauge itself (2) the sock or the line rearward from the pump (hookup a gas can to pump inlet to confimn/eliminate both)

What kind of gauge is it and how and where is it plumbed in??

Check the small section of connecting hose back by the gas tank. If it's in bad shape you could be sucking air into the fuel line.

The gauge is a screw in type at the daul line at the carb (Mr. Gasket). That little hose at the sender was just changed out. I will bypass the gauge 1st then will use the can method before the pump. Thanks to all

Is it a liquid filled??
If it is liquid filed they are real sensitive to heat changes under the hood. as the temp goes up they read lower and lower even though the fuel pressure actually stays the same.

I posted this a couple of weeks ago, I hope it helps!

Last night I missed out racing at the only 1/4 mile event for the year that is within 1 hour of my house! I hope after reading this it will not happen to any of you.

My car was surging at full revs but the trans was playing up as well so I took monday & tuesday off work to sort the trans, got it back together on tuesday arvo & out to the tech inspection at Mosgiel on tuesday night. After that I give it a bit in 2nd going up saddle hill (steep 3 laner) it started to surge although the A/F still looked OK but it did feel like a lean surge. I backed off checked for lights & sirens then back into it again, this time the A/F went to [Edited by Moparts - Family Friendly Site - Keep it clean] so I took it quietly back home.

Suspecting a blockage rather than a fault with my 1 year old pump I changed the filter, blew out the lines, replaced all rubber lines just in case they were bad on the inside, remover the sender unit & removed the filter from in the tank. I fitted a fuel pressure gauge above the hood so I could see what was going on, 6-6.6 psi at idle & low load, 3psi at about 3K & almost 0 at 5K under load.
I swapped the fuel pump for the original one that was still working when removed (& tested with good pressure & vacuum on the bench) only to find it was worse, this was 1 hr before the event I was entered in.
Next I checked the stroke of the fuel pump pushrod & that of a new comp cam I had to see if the cam had worn, 2% wear at most, not the problem.
Then I measured the relative position of the pump pushrod & the arm on the pump & things did not add up.
I phoned the Dude running the 1/4 to pull out & he said if I turned up late I was still in.
We tried for over an hour to get that poxy little plug out that gives access to the pump pushrod & at 7pm I gave up
Today with a bit more time & effort the plug did come out & I got to see that little piece of metal that caused me all this drama.
I can't believe how much pushrod is worn, both ends were worn hollow, .018" deep on the cam end & .022" on the pump end.
There was major wear on the cam end leaving an effective pushrod length of only 2.874" which is .368" shorter than the MP P529569 pushrod ( 3.242")
This is why I had no fuel pressure, the effective stroke was so short I wasn't getting enough volume of fuel to build any pressure.

My advice to anyone with a bigblock -

Any time you are building an engine, changing a cam, changing a fuel pump (mechanical) or have any fuel issues at all take that damn plug out, remove the pump pushrod & check it for wear!

It is liquid filled.

My motor was rebuilt last year and I doubt the pushrod was changed. Glad you got it figured out. It's raining bad here today and will do the other checks 1st as soon as I can.

Beware what was said about Big Block fuel pump pushrods. There are alot of bad/improperly heat treated new ones. They can wear in a hurry !

""It is liquid filled.""

That might be the problem. As mentioned ealier, the liquid filled gages are affected by the ambient heat in the engine compartment. Try one without liquid to see if it reads the same.
I had this same problem with a liquid filled unit. I replaced it with one without liquid and everything was fine.

Glad you found it make sure you run oils with lots of zinc. That is what is needed for metal on metal. once anything starts to wear you get past the hardening and then they wear fast!! cams too!!

Just had the same problem,I went to yearone cruise in Saturday in my 71 rt charger and the damn thing quit as soon as I pulled in.I changed the pump and it ran again but was a weak gas stream so got back home pulled the push rod and it was wore down .250 on cam end so I put in a good used one I had and now it is pumping like mad.The motor only has 1000 miles on it so I am thinking cheap aftermarket push rod.I have attahed a pic look at the grey part of the ends and on side is way shorter thats what is worn off.

Where the best place to order one? All my local parts stores have to order it as well. I found part #FP1021 AIRTEX

I would say the one that mopar performance sells would be a good one.

I just bought one from Mancini for about $14.

Thanks, just ordered one.