Fuel pump quit working in my wifes LS1 several months ago. I checked the relay out of the car. It was good. I checked for voltage to the relay 12 volts. Fuse is also good. I assumed it was the pump and put it on the back burner till today.

I bought the expensive *** pump and went through the nightmare of installing it. Got it back on the ground and hit the key still nothing

I started rechecking everything. I touched a 12V jumper to the pump side of the relay and it come right on. I have 12 volts with the key on to the activation side of the relay that comes from the pcm.

When I jump this wire through the relay to the ground side of the teminal the 12V shuts off.

What is causing the pcm to shut of voltage as soon as it trys to complete the circuit through the relay? Do I have a bad PCM is something malfunctioning with the anti theft? Please help!!

 

start with the simple things since you already did the hard stuff, is the security light on the dash all the time?are you using an aftermarket key? im not an expert, just have a few sitting with me going thru the posts. none of us think their is a crash sensor for the fuel to reset in the trunk or anywhere else. could be wrong, dont have my owners manual. i know you said you jumpered the 12v over and the pump came on, but did you test continuity from relay/12v sorce to the pump?

 

The worst thing ever just happend. I gave up last night and came inside. I just came home and went outside to try to figure it out. As soon as I hit the key I heard the pump and it started right up.

To give a little history this all started one day when my wife called my from the mall to say the car wouldn't start. I was at work so I just had it towed to the house. I went out the next day to diagnose the problem. It started right up.

I gave to back to her and said I can't fixed what isn't broke. A few days later I got a call that she was broke down again but this time stuck in traffic. I towed if home again and this time it didn't start for me either. After doing a few tests I determined I thought it was a bad pump. Fast forward to today now I am in the same boat I started months ago.

 

my car used to do the same thing ur wife had happen to her and it would start up to

it was my pump
hope u figure out ur problem man

 

Its fixed!!!!!

I am posting my solution in case someone in the future has a similar problem.

I went outside to pull the car in the garage for the night and it wouldn't start again. Determined to figure it out I pushed it back inside the shop. I tested everything again and all the tests came out without problems. Voltage is everywhere it was susposed to be but pump would only come on when I hot wired to the pump side of the relay terminal.

Even though I had good 12V from the fuse to the fuse side of the relay I decided to double check continuity. Ohms were extremly high. I started untapeing the harness to look for a short or a bad section of wire.

Turns out at some time in the cars life a previous ower had installed an alarm or other device to kill power to the fuel pump relay. They did a very poor job of splicing it back together and the crimped terminal was barley making connection. Soldered a 3" piece of wire to replace the splice and it started right up. :yay:

 

Crappy alarm/stereo installs cause a LOT of problems just like the one you described. Been through it myself...glad you got it figured out.

 

Good troubleshooting! In my line of work we call those buddy bugs.