Ok 1973 L82 runs well until the fuel gauge indicates less than a 1/4 tank, that’s when it starts to bog down, miss, pop sometimes.

I fill it up drive it a bit and it reverts to normal.

I’ve only owned the car almost two years and haven’t dropped the tank or replaced the fuel pump. It does have an edelbrock carb and performer along with stainless long tubes.

Anyone have any suggestions other than to fill up at 1/2 a tank?

 

Fuel pick-up not on the bottom of the tank? Small hole in pick-up tube? bad pick-up tube filter? I would be pulling that out of the tank. On my 77 yes I have to pull the tank.
But on a 73 I am no expert.

 

All of what @4-vettes listed in his post should be checked.

Another question is, how much fuel does it take to fill it when "the gauge reads 1/4 tank?" If it takes more than 3/4 of the tank capacity, the gauge sender may be sticking or obstructed.

Also, are you using a stock mechanical pump? Or has someone installed and electric pump?

 

H-m-m-m-m-m.
Does a '73 tank have a rubber bladder that can collapse?

 

I would think your gauge is off, the pickup isnt all the way into the bottom of the tank and you might be sucking air as the fuel sloshes around. Or your fuel line is run in such a way that the head pressure isnt getting all the fuel to the mechanical fuel pump to keep it supplied and you are actually out running you fuel. As the fuel level goes down there is less pressure from its own weight to make it past a kink or obstruction. As you car stalls the fuel can make it back up the fuel line to the pump and there you go again until it gets air bound again. I believe the 73 is fed off the bottom like the 68 and you should still have the huge hole in the filler to see how much fuel is in there. Can you use a flash light to see how much is in the tank and where the fuel sock is? An expensive solution is the fuel mat that Holey sells. Its used with the Holley Sniper system and its like a Sham-Wow for fuel. It would draw the fuel up into the line

I believe the only way to tell what is going on would be to record how much is left in the tank by filling it and recording the capacity a few time to see if its repetitive at the same amount of fuel. If it is then its the pickup level or fuel line specific. If it is make sure there are no kinks anywhere in the rubber bits of your fuel lines. there should be rubber a the pump and at the tank. Drain the tank when its starts to stall and record the amount. If its less than 2 gallons there might not be much you can do other than remove the pickup and try to straighten the pickup so that it gets to the deepest part of the tank. Maybe use an air hose and blow back through the fuel line towards the tank and see if anything comes through into the sock, or remove the rubber before the tank and blow from the pump to that point then from there into the tank to minimize blowing crap into the tank maybe you have rust in there. Our tanks are wedge shaped to the part closet to the cabin is the lowest point so looking into the tank you are actually seeing less fuel than you think. My tank has a seam that looks to be at the half way point but is actually at the 1/3 point due to the wedge.

When I pull my fuel line off at the fuel pump with head pressure will force a good amount of fuel out. You can also get it to the stalling point, raise the car high enough to get a 5 gallon bucket or drain pan under there and disconnect the fuel line and just let gravity pull it to the bucket. It should be a strong steady stream, if its poor then you have an issue at the tank or in the line. Let it flow until it stops and see if there is any fuel left in the tank.

Generally if the issue is past the fuel pump it would be there all the time, not just at a 1/4 tank.

 

bladder?

That just remionded me of my Bike!!!
THats something that happened to my Honda, the vent would get clogged and it would stall as the fuel got lower because of the suction, when I openned it up it would Pop then it would be good again for a while as it built a vacuum again. Does yours make a sucking sound when you remove the gas cap?
Is the 73 cap vented like the earlier ones. If you have an evap system built in it could be clogged or the vent could be clogged. If you can get an earlier gas cap that is vented you could experiment with that to see of it relieves the issue

 

The 73 has no bladder and it is non-vented.

Donnie

 

Maybe the evap system is plugged, the tank has to breathe

 

I did away with the evap system on mine and drilled a pinhole in my gas cap. That was 17 years ago, although I suspect that is not your problem. I was having gauge issues in my '68 Chevy Van, so I ordered a new sender, but before reinstalling the tank I did this. I started with the tank off and dry and hooked up the gauge with jumper wires. Then I added fuel until it would come out the pickup tube (manual vacuum) and noted the gauge reading. This is the running on fumes level. Then I added a gallon at a time and noted the gauge reading. after 3 gallons. I installed the tank and went to the gas station. I then continued to add a gallon at a time and noted the gauge reading. I did this until the tank was fuel. I made small chart and now I know how much fuel is left at any gauge reading. Turns out when the needle hits E, there's almost 3 gallons left. Sometimes the sender pickup does not extend low enough in the tank and can be bent slightly. Or your float might be shot, or the swivel worn or any number of things. It might cost you nothing to fix.

 

thanks, sending unit is accessible from the bottom of the tank. will try this method

 

gas cap is OE and non vented