1998 Buick Lesabre runs out of gas with about 5 gallons in tank?

[Mike D 1998]

I had the fuel tank, pump and sending unit replaced. Gauge appears to read improperly, but it appears to run out of gas
and when we fill it up, it takes like 10 or 11 gallons then runs fine until we get close to 1/4 tank then ( so we dont run out again) we will up and it takes about 10 to 11 gallons.. It happens if car is on slight hill with nose pointed downward. Before a tear into it wanted to get some ideas?

 

[MelsRegal]

were the sending unit and pump new or used? What happens on the slight hill?

 

[Mike D 1998]

Fuel pump and unit and tank all after market. On slight hill with 1/4 tank gas. Car runs out of gas and stalls. When we refill. It takes about 10 to 11 gallons so i assume the tank is not empty.

 

[DonP]

Sounds like the pump and/or tank are not the right one for the car, the pump loses suction when it shouldn't.

 

[Mike D 1998]

Sounds like the pump and/or tank are not the right one for the car, the pump loses suction when it shouldn't.

I was thinking that perhaps the Pump and sending unit were too short... thats why it leaves about 4 to 5 gallons at bottom of tank... Does anyone have a picture of what the tank should
look like so I can see if the outside matches? Again before I start tearing into it.