I replaced fuel pump on a 2000 Silverado a week ago and it works till now. WHen key is on there is no power going to the fuel pump. Also the wire has light dirtyness to it. I had a extra power source and the pump works. I also just got my battery tested and it says it needs to be replaced. IS it the Battery? or the wiring harness? or the pump?

I think you answered your own question on if its the pump itself. if you had an extra power source hooked up and it worked then that tells you that is good.. i would try replacing the battery (whether its the problem or not it needs a new one to run anyway.) Think Logically. when you turn that key not only is the fuel pump looking for power. so is the starter the ignition control module. dash lights Daytime running lights if your truck has them and umpteen sensors are begging for power too. someone is the low man on the totem pole and with the fuel pump being the farthest away i would guess thats it.

Electricity is lazy. it takes the shortest path to ground. If it can go through this sensor to get to ground easier than running through the fuel pump then its going to.

one thing that might work (i haven't tried this i just spun this idea off the top of my head) is hook your truck up like your going to jump start it and try to start it and see if that second battery gives it that little extra umph to start.

I'd definitely replace the battery first if it is bad and not just discharged. (testing should be first charge, then load test) Once the battery is correct, then if the fuel pump still is not working, probe the wiring behind the harness plug to make sure the plug connectors are not faulty. Also check the pump relay and fuse. Likely you will find a problem in one of those areas. Actual harness wiring rarely fails unless it is worn through and shorts out. Plug connectors however can sometimes develop corrosion inside where the wire connects to the pin. I'm not sure what you mean by light dirtyness...if it is dirty on the outside casing that's normal...everything underneath gets dirty. Pins and other parts of the connector can be cleaned and often that will help but generally that will result in low power not complete loss.

1st replace your battery and if theres no corosion on the wires of the harness it should be fine, make sure to check and replace your fuel relay if needed. If the pump has a warranty return it for a new one. good luck

Have you checked the fuse? Whenever i replaced a fuel pump in a truck like yours i've had to splice in a new connector supplied with the fuel module. If you had to do this, double check your connections. If that checks out ok, jump the fuel pump relay out by jumping the pin that gets constant power to pin 87. If that turns on the pump, check the relay operation and verify the computer is sending the signal (ground) to turn on the relay. If it doesn't turn on the pump, check for a break in the wire between the relay and the pump. Maybe you pinched a wire when reinstalling the fuel tank?

If you have a bad battery,and the battery has a short in it,it is possible the fuel pump will not run.If the battery is charged with ac voltage,witch if the alternator diodes went out ,and it was charging ac voltage,it would explain the problem.But have the alternator checked also.

CHANGE BATTERY,AND WIRE ,THIS IS ALL YOU SHOULD NEED!