Motor will fire off and run for about 5 seconds or then
shut down.
I've checked the fuel pressure and it's pretty constant around 30 psi and when motor shuts off the pressure jumps to about 37 psi. Also we've checked to make sure the coil was firing off as it should and that checked out ok.... any help or suggestions would be appreciated on what the problem could be.
thanks.

Does it cut off clean or does it stumble and then cut off?

Is it seeing oil pressure?

Yes it cuts off clean and it does see oil pressure.

What kind of EFI system do you have?

502 magnum mpi

This at cold start, or after you've been running for awhile ? Sounds like vapor lock.
I think a little more background will get some better answers.

Cold start up now.... the vapor lock issue has been fixed by returning fuel back to the tank. The starboard side motor runs fine though.

Don't know if you have cool fuel or VST. Could use a bit more info as to the engine setup and what it was doing before this issue. First thing is I'm thinking it may be the IAC. Can you give it a bit of throttle and see if it will continue to run?

Vst..... you can give it throttle but dies right out. It literally runs for 5 sec. Everything was fine before and it ran great.