Fuel pump power being cut off after less then 3 sec

Need to know what make and model car you have along with year and engine.

ECM controls ON/OFF operation of the fuel pump by turning it ON via the fuel pump relay under any of the following condition.

-For 3 seconds after ignition switch ON.
-While cranking engine (while engine start signal is inputted to ECM).
-While CAS signal is inputted to ECM.

So with that being said, it sounds like the first 3 seconds is working fine. But no power in the start mode leads me to belive there may be a problem with the engine start signal. Check pin B11 on the PCM to see if you receive 6-10 volts with the starter engaged. This is used for the start signal. If the ECM is getting that signal, but not running the fuel pump, it is probably bad.
Have you tried to supply power to the pump circuit and get the car started? This would eliminate the CAS crank angle sensor which supplies the signal while running.

This is called a ECM Engine Control Module and it is located under the left dash. If you remove the left speaker cover by your knee, you should see the ECM attached to the fuse box. On the end there are two connectors that should be labled A and B.

I was told there is a plug in the engine compartment that can be use to test the fule pump " I did not find it yet" I have cleaned all the grounds. I guess my next step is to put power to the fuel pump to make sure it's ok, Tomorrow I am returning the ECM I got at the local car recycler he will give me an other one so I'll be able to test it cause last week when I pluged in the replacement ecm the truck worked for about 2 hours, but I really want to find the source of the problem which cause the ecm to fail in the first place. I was also thinking to grap a spare distributor and replace it to make sure it's not the ignitor which is causing the fault. Thanks for all your help

Bleu[/quote:626b9a5653]

I thought you said the fuel pump ran for 3 seconds when you turned the switch on? If you remove the fuel cap, and listen in the tank when you turn the ignition to the on position, you should hear the pump run for 3 seconds. You can also feel the fuel return line behind the filter and feel the pressure on the return line. If both of these tests are good, then your pump works fine. If the trcuk runs fine when you get it started, then the pump is fine. It just sounds liek you are not getting good fuel pressure during start.