Howdy, just wondering, Since I got my '77 pickup 5? years ago, I've run it out of gas about 9 times. First time was me and my folks thought it had a 10 gallon tank so we were only filling it about that much. It has a 16 gallon tank. The rest of the times were addition errors and optimistic fuel mileage assumptions. The gas gauge don't work. So my question is, when I take it into the station after sticking 2 gallons in to resuscitate it, it only takes 13 more gallons. Is there an extra gallon that never gets burned at the bottom of the tank? So in actual fact I have a 16 gallon tank with 15 usable gallons?

 

You are carbed. So all you have is a steal fuel lined running down to the bottom of the tank with a slight curve on it. The bottom of your tank is flat. It doesn't have a sump in it. When your out of fuel there's still fuel in there that's not getting suck up by the pump only because the fuel is bouncing around in there. Hopefully you understand what I mean.

 

Are you saying that I have a mechanical fuel pump with a line that goes into the tank like a straw? Because I have an electric in-tank pump.

 

Your pump is mounted on the engine but yes the line goes in the tank like a straw.

 

Anything past "E" doesnt count as capacity, more like reserve and your lucky for every mile you travel. So run it down to "E" then fill it. Theres your answer.

Hopefully it wasnt this hard for you to learn to tie your shoes also

 

If you have a '77, like you stated in the first post, it would be mechanical pump/carb'd. Unless someone has done a swap. I can't think of any low pressure, in-tank pumps except maybe an older diesel lift pump?

 

As stated previously my fuel gauge doesn't work so it's a little hard to run it down to E when it's already at E. Like I said, sometimes I add the miles wrong, and sometimes I'm a little too optimistic. My question was, why does my truck run empty at 15 gallons when it has a 16 gallon tank. For the 1975-79 pickups, they used an in-tank electric fuel pump then switched to a mechanical engine mounted pump for the 1980-83 models. Not sure what they used for the pre-'75 models. And not sure why they switched to a mechanical pump. Maybe because dropping the tank is a real pain.

 

Ok just realized, probably some of the capacity of the tank is taken up by air and vapors. and then when it's empty the pump doesn't quite get the remaining .17% gas at the bottom. Pointless thread.