I noticed my fuel filter is completely empty after my car sits for a day or two. Don't see any leaks, and I changed the gas cap in case it wasn't venting. Will fill with fuel and car starts and runs after I crank it a little. Is it normal for fuel to drain back through the pump and into the tank?

Its a 1971 318, mechanical fuel pump, one filter in stock location, Edelbrock 600 cfm carb.

I fuel filter is usually never full, even when the engine is running.. You say you can "see" in it. Do you have a glass filter or a plastic one? Either way Id recomend changing to a metal filter for the sake of safety..

Probably evaporating.

Yes, its a clear plastic filter. I normally use a metal one (which also emptied after a day or two), but switched to this plastic one so I could see if anything was collecting in the filter (its clean). When the engine is running, the filter is about 1/3 full, which I think is normal.

Is there a check valve or a seal in the stock fuel pump that's supposed to stop gas from draining back? Other cars I've owned always had some fuel in the filter, though the filters were located further away from the engine in a more "level" location and those cars had electric fuel pumps.

You should have enough gas in your carb that it should not matter either way as it should pump up right away with just a normal factory fuel pump when started.

The factory pump has a check valve. It may not be sealing completly or the gas may be evaporating as posted above.

no, it shouldn't drain. mine did, ended up having a small leak in the hose tying the hard line to the fuel pump inlet.

on a BB engine the fuel pump can ruptur and dump fuel in the crankcase and kill the engine is short order.

on a SB engine the fuel pump has a weep hole that will let the line from carb to fuel pump drain down.

check to make sure the pump is not ruptured and leaking the fuel.

some of it is heat soak/fuel perk/evap with the crappy gas. the ethel will evap very fast and need to refill the bowl on start up.

you can add a check valve in the line,but a good working stock system should hold the fuel for DAy or so. IMO..mine does.

also check the steel line from tank to pump,small pin holes can leak undetected.

i found mine was full of pin holes you could not see,till after I slaped it on the floor a couple times to dislodge rust on the line. very plane to see after that.

what carb is it? some fuel bowls need to be epoxied at the jet well plugs for internal leaks.

Thanks. Yes, after a few days it takes a little more to start it. I think everything after the fuel pump goes dry.

I'll check everything after the fuel tank for leaks. Some sections of metal fuel line are original, still covered by undercoating from 40 years ago. There's no obvious leaks, but I've never examined it closely either.

Carb is an Edelbrock 1406, 600 cfm.

seems to me most eddies have this kind of leak down. they will perk the fuel if the carb does not stay cool.

I use a 1" stacked plate/gasket 4 hole heat disapator under mine that made 90% of the trouble go away.

after a 40 mile ride you cant touch the intake but the carb stays luke warm to the touch. may want to see if yours is heat soaking after a run also.

heat soak when it is shut down evaping most of the fuel in the bowl then after a day or so the rest evaps out the vent.

does it have any bubbles in the filter when running? a sure sign it is sucking air.

look for dampness around the fuel pump weep hole on top,that will let it drain down to the fuel level in the tank.

it wont siphin fuel from the carb so it may be perking the fuel into fumes.

good luck,post back what you find.