47-55.1 Truck wouldn’t start on angled driveway?

[NeoJuice]

1952 w/chevy 350 w/edelbrock 1406 and edelbrock mechanical fuel pump. New OEM fuel tank behind the seat.

As I'm getting closer to inspection and checking the last couple things off the list I decided that the truck needed to be started since it's been a couple weeks since starting it up.

I put it in neutral and gave it a shove out of the garage and out onto the driveway. You may be thinking to yourself why would I do that? I didn't want the garage filling up with fumes and possibly trailing into the house.

I gave it a couple good pumps and turned it over and over and over until I killed the battery. I pumped the pedal over and over again and it would not start. So I got my ford and hooked up the jumper cables and let it charge up and still the same thing, it would not start. I tried even adding about 1-2 tablespoons of gas into the carb and it fired up for like a split second then died.

So I got my neighbor to help me push it back up into the garage and there she sat. I go out yesterday after having the battery on the charger for close to 24 hrs and decide to start the truck. I gave the pedal two pumps and turned the key and she fired right up.

Now I'm confused. I was thinking of all the possible scenarios that could be happening. Clogged fuel filter? Bad fuel pump? problems with the carb? the tank had 3/4 of a tank of gas in it.

If the truck wouldn't have started I was going to replace the fuel filter to start. Then after that look at the fuel pump but like I said it started no problems on the flat garage floor.

I'm thinking that drain back to the tank might be a problem. I was looking online and found that possibly installing a check valve after the fuel filter and just before the carb might solve the problem with angle parking or the truck sitting for an extended amount of time.

But I'm wondering the the pump could be going bad because shouldn't the pump act as a check valve in some fashion? The fuel pump was on the engine when I bought the truck and I'm not sure how old it is.

https://www.summitracing.com/parts/rus-650603?rrec=true

I would appreciate input from fellow forum members on this issue.