I have been working on my engine swap for awhile now and im just about done. Its an 87 with engine code H, I swaped in a carbed 355 i ussed a holley 85 gph mech pump.

I have everything pretty much wired up and i tuned the ignition to on to check voltage to something and the fuel pump in the tank kicked on and was pumping gas through the mech pump on to the ground. when i turn the ignition back to off its dousn't shut off unless i dissconect battery power.Its not constant just when i turn the ignition.

Im guessing it has something to do with all the computer controled crap the car had. Is there a sensor that tells when to shut off the pump or is there something else to fix this problem?

 

The system doesn't act that way when stock. Without knowing what kind of crap you did to the system, it's pretty much impossible to say why it's doing it now. Obviously, you did something that is sending power to the pump that doesn't shut off when the key shuts off - sounds a lot like a relay issue.

What had you planned for the stock electric pump? Unless you expect to use it, it should be removed. If you use it, you need a regulator.