Help!!! 1996 S10 Blazer fuel problem

We have a 1996 S10 Blazer with a 4.3 V6 vortec w-code engine.

1. can an after market alarm ssytem stop the engine from getting fuel? 

we have 60 pounds of fuel pressure to the fuel rail at the intake and I still have no fuel getting to the injectors.  Could it be anything else other than the spider injectors or fuel pressure sensor located on the top of the intake.   And is the feul pressure sensor just considered a map sensor.  If I pour gas into the intake the engine starts up until the gas runs out.  I have spark and I did not have any problems with fuel up until the engine would not start with the key so I had a dealer disconnect the hot wire from teh alarm and hook back up the original wire.  Then it started with the key again and ran fine for one day and when I tried to start the engine the next day there was no fuel.  Since then I have rehooked back up the alarm the way that it was and it now cranks fine but does not get any fuel. 

Does the computer have to send a signal to a sensor that I am unaware of to allow the fuel to pass through the fuel rails into the spider injector?

I have also checked to see if I have current to the spider injectors and I do.

If anyone has any information that you are willing to share we would be very greatful.  or if anyone has had the same problem and can tell us what they had to do.

Thank you.  Our email is christywalter@yahoo.com.  Thanks so much.

christy and paul