ok, first, if i`m a pain in the neck, shut me down. period.so, a year or so ago, i thought i had this licked. put on an electric pump, rated at 4 pounds. ok, ran good, constant 3, minimum , thru the mechanical. now, out of the blue, other nite coming home from a cruise nite, opened margie up, layed down at 4 grand. opened the hood, on the gauge, zero. so, just now, by-passed the mechanical, started at 3, down to zero, in the driveway, 2000 rpm for 30 minutes. i know i did this before, but i`m going to drop the tank, check the sock, EVEN THOUGH it`s the 3rd sending unit.ok, just a thought, ya need the vented cap, right? so, i have that flap in the filler neck. could that be the "not" venting problem? again, shut me down, i`ll just put a bullet in my head. nyuk, nyuk, nyuk.
thanx for the questions, you guys. i thought i had this licked with the electric pump. i just by-passed the mechanical pump, same crap. ok, vented cap, does it with the cap off. 3/8 line all the way. out of tank, outside of frame, electric pump, in line filter, insulated line starting 2 ft. from mechanical pump. in-line gauge, just before the edelbrock carb. edelbrock insulator under carb. i won`t get to it now, till the weekend. however, going to run a fuel line into a can, just before the electric pump. that one-way valve" in the filler neck is in the back of my mind. again, thanx.
It's almost impossible to judge what you have, you have so much.
Here's some things to think about.
1. As you pump fuel out of the tank, the volume of fuel has to be replaced with air. That is the function of the vent. If you have a "one way" valve in the filler neck, and if it really seals, then that's no good. No fuel gets out if no air gets in.
2. Electric pumps don't pull much if any vacuum. So an electric pump needs to be gravity fed, or immersed in fuel inside the tank. Otherwise it can lose its prime.
3. A properly working mechanical pump doesn't need a gravity feed, even with a fuel line that runs the length of the car. It can't pull fuel through an electric pump.
4. If you have "vapor lock" problems with a mechanical pump, they are most likely going to occur on the suction side. Fuel pressure compresses vapor bubbles, makes them smaller. Vacuum makes them larger, and pulling a vacuum on vapor won't make liquid move.
5. There's no real sense in running both a mechanical and an electric pump. They don't cure each other's limitations.
What pump are you using? Carter 4070 or something else? Can you describe where it is mounted?
Rick, a mechanical pump can pull through a carter 4070, maybe not others but the Carter it can. I ran that set up for decades but used the electric pump primarily at the track when the mechanical pump was not keeping up with the multi carbs. Carb bowels running dry was only an issue at the track so I only used the electric pump at the track, and priming the system when the car sat for a while. Other then that, if was off and the motor ran on just the mechanical. I just changed over to all electric pump because the mechanical pump pulsing was wrecking havoc with the weber carbs I am currently running (read that touchy carbs). Cant say about other pumps.
At any rate, running at 1 pound is not sufficient even for my webers that require 3 so I am sure the edlebrock requires 4-6. so that is why I asked what pump. HHDude, I dont think I am far from you. I may have a spare new 4070 if you are running a 4070 and want to see if maybe you have a bad internal pressure relief in the 4070 you are running, if you are running a 4070.
i am using a car pump, rated at 4 psi. edelbrock carb, nothing more than 6. ok, playing it safe. your pump, intersted in. can ya run that, justy that, all the time? long trips? i`m ready to buy a pump. i just ran a line from the inlet to a can, to eliminate everything back from the pump. still no good. pump is located just in front of rear wheel, outside the rail. but everything w3as great, till bam.
Can you put a fuel pressure gauge inline right before the carb? tape your smartphone and video the gauge while take Marge out for a beating....
I don't know these Edelbrock carbs but Rochesters and some Holleys have a brass filter cartridge built into the carb right where the fuel line enters the carb.... you might consider changing that if applicable...