1998 olds 88 won't start when car is parked on steep hill with nose down (fuel pump, fuel filter and pump screen have been replaced, and tank is full). Also, when driving car up hill with a steady pressure on the gas pedal, car will sputter and act as though it's running out of gas.

The same thing happened to me many years ago. It was not out of gas but it was so low that the gas wasn't reaching the fuel pick up hose in the tank, at that particular angle.
I coasted down the hill to level ground and it started easily.
Try putting some gas in the car and try starting again on the hill. If it still won't start then something else is wrong, but I have have no idea what it could be.
Good luck

SUNDS LIKE THE FULE PUMP CODE BE BLOCKTE

Have you changed fuel filter? Sounds as if debris is back lodging in filter when parked on steep angle. Just a simple suggestion

check fuel filter and make sure its not clogging up, make sure the engine is getting fuel, have someone go under the car where the fuel tank is and have them listen when you turn the key to on to see if there is any sound coming from in the fuel tank, if not, then you may have burnt out the fuel pump. Fuel pumps are Great for randomly going out at a moments notice. those GM v6 engines dont jump time easily so it more than likely wont be that.

could be getting an air lock in the fuel line somewhere

There are two things you will want to check: is your vent tube clogged up, and is your fuel filter clogged up? It might be an internal-tank fuel filter.

Do you park on a hill? Try pumping the gas pedal a few times before you start it. Check that there is no fuel being dropped, check under the car for rusted fuel lines and any drips.

Hope this helps and vote for me please Thanks.

If you have a 30 gallon tank this can happen on steeper hills. the sending unit holds the pump in a canister that holds about a quart of fuel. if the canister is not sitting in fuel it willnot **** it into the canister. when the fuel is used in the canister your car dies. pretty normal. hope this helps

It depends: how steep are the hills? Assuming you have the standard 4-speed or 5-speed gearbox, it's likely that the tiny engine (built for economy, not for power) is simply not generating enough torque to pull the car up in high gear. Have you tried simply downshifting? If the problem truly is the engine losing power and not just lugging due to being in too high a gear on a steep grade, you should check your fuel pressure and you may also want to check the condition of the fuel pump and feeder lines inside the gas tank. A 20 year old car will probably have some disintegration of the feeder lines, they may even be partly broken off inside the tank resulting in poor fuel flow, or disintegrated rubber may be gumming up the strainer or the pump itself. Personally, I'd replace the fuel lines, fuel filter and if low pressure still exists, the fuel pump as well.

There usually is a strainer in the gas tank. After 23 years, anything is possible. If you have a carburetor, replace it, or have it cleaned. If fuel injected, the big hose from the air filter could be damaged and shifting loose. If the engine doesn't see the right vacuum, it won't work right. Check all the little vacuum lines. Get a vacuum gauge, learn how to use it. Do a fuel flow test to see if your tank is clogged.