91 LeSabre Fuel Problem

My 91 LeSabre starts great only with a full tank of gas. Once gas level gets down three gallons or so from full, it won't start - even less if on a slope facing downwad. ???

perhaps you fuel pump is on its way out. this may be a good thing(wont leave you stranded) or a bad thing. if your not mechanically inclined and dont have access to a decent garage where work can be done by you, repairs could be costly. 1000+ dollars. but maybe lower like 3-400$. since i havent seen your vehicle or what type of condition the underside is in, it is very hard to tell. on a + side, you may have a blockage of some sort which wont be as costly. start by making sure your injectors are firing on all cylinders when the vehicle stalls. im sure someone else can take it from there.

My 91 LeSabre starts great only with a full tank of gas. Once gas level gets down three gallons or so from full, it won't start - even less if on a slope facing downwad. ???

Either the fuel pump, OR the fuel pump strainer.

The fuel pump strainer is bellow the pump, and is the first filiter/strainer to become clogged up from dirty gas and dirt in the tank.
It will surely affect he fuel pump from sucking up the gas in the tank.

Most people say if u going to replace the strainer, replace the pump also. But on my 93 I replace the strainer and not the pump, and she is just fine now.