How do I change a fuel pump on a 1999 buick regal

One is for the fuel delivery, one is for the return and the other one goes to the vapor cannister.

I can't imagine how that would be possible unless something in the fuse box or wiring harness was damaged while you were working on the axle.
I would check the fuel pump relay for power and see if it is sending voltage to the pump. You may need a book to get the wiring diagram for the circuit.

Sounds like a possibe fuel problem. Fuel filter or pump possibly. Check filter first. Much cheaper!

if the new pump did not come with a level sensor thats the part that fails it the part that has the float arm on it

It sounds like a fuel pump resister. I had exact same problem with my regal, resistor has 2 black leads, ceramic and it shapes like horse shoe. mine cost $79.95. Before I know this, I had the dealer replaced fuel pump, fuel filter still didn't fix the problem, and they suggested injector madulator. Very fortunate I ran into a friend has the same 1999 buick regal V6 SC and had same problem told me about this fix. I called 4 buick dealership parts dept.and asked to buy a fuel pump resistor they all told me that there no such thing! So, if want this p[art go to GM parts dealership.
And ask them to show you where it locates. Because it hidden inside engine compartment.

Hope it'll fix your problem like it did mine.

Owen S

In the fuel tank

it's a voltage regulator on the fuel pump , located on the fender underneath battery. just replaced mine ,same problem.

Open the trunk. Pull the bottom liner free from the trunk by hand, then remove it fully from the vehicle.Remove seven nuts holding down the fuel pump access cover, using a wrench. Lift the cover up and off the cover studs.

Remove the fuel pump retainer with a pair of inside snap-ring pliers. Carefully lift the pump assembly out of the tank. Use caution when handling the pump assembly, as the float and float arm are delicate and can be easily damaged.

Carefully pry the fuel filter off the pump intake nipple, using a flat screwdriver.
Reverse the disassembly steps to reassemble the fuel filter on your Regal.

but what the pressure it should be at

A couple of possibilities. 1st, check to see that the fuel pump is working. When you turn the key to on position (not all the way to crank the engine over), can you hear the pump? You should hear a humming sound from the gas tank . The fuel in the tank actually keeps the fuel pump from overheating. It is possible the pump is shot. It would be a good idea to change the fuel filter, as it may be plugged up from sediment from the bottom of the tank.