97 Sierra Fuel Pump Problems!!!

I have a GMC SIERRA 1997 4x4 K2500 5.7L with 176K miles. Just replaced the fuel pump and sending unit, not to mention the fuel filter and relay. so now when i try to start the truck, no whirring or anything. So let me start from the beginning, no fuel pressure so replaced pump, hooked back up and still wouldn't work in the tank even if i jumped it at the terminal to bat.+... it worked outside the tank and dry but not submerged in gas, replaced sending unit and now it works only when jumped, but at least now it will do it in the tank. but it won't start if I turn the key like a normal person. I have sanded the rail where the ground goes and cleaned the connections. the ECM-B fuse is good and as i said, I replaced the relay. the battery is at a full charge of 12.3 volts. The ignition switch doesn't have anything to do with the pump... right? and the ECM can't possibly be bad... can it? please help.

The fuel pump starts pumping as soon as the key is turned to run.

Try replacing the plug end that goes into the fuel pump. I had the same problem with a 1998 Sierra. i replaced my fuel pump and sending unit for nothing. All that was wrong was a broken wire on the plug. I got a new plug in at a local parts store for about $30. They should sell a pigtail assembly for the fuel pump connnection. I went to GMC first and they wanted to sell me the entire wiring kit from the fuse panel back to the tank for $100.

The factory connection that hooks to the fuel pump fails on these models. Aftermarket replacement pumps come with a heavier duty connection to fix the problem. If you did not replace the connection coming from the wiring harness you still have the original problematic connector. Did you buy a new pump assembly or is the replacement you installed a salvage unit? Look at the connections, they're most likely fried.