Chevy starts then dies

I have a 1987 Chevy 5.7 liter 350. Recently I changed the truck over from throttle body to carbuerator, took off all emissions and also switched to mechanical gauges. I put new intake,distributor,headers, and a fuel pressure regulator. I kept all the wiring that was not needed tied up just to make sure everything was going to work properly. The only wires that were left around was a brown wire going to my alternator and the pink wire that used to go to my coil for the positive on my new coil. Everything was perfect for a couple of months until I decided to get rid of all those wires. I started by taking the two wire harnesses out of the computer under the dash on the passenger side and another harness that was close by. I then passed the wires through the grommet on the firewall and moved them to the drivers side to go from there, in the process having to take off my distributor cap. I then went to start my truck only to find out that it would run for about 30 seconds and then die. I removed my computer and temperarily hooked the two harnesses back up plus the third harness that i had to send through the dash. Just to find out i have the same problem. My fuel pump does primer when i turn my key on. I've tried putting gas in my carb bowls but still the truck only runs speratically for about 15 to 30 seconds. I would appreciate any help I can get. Thank You

After it runs for the 30 seconds, can you immediately restart it and get it to do the same thing (for 30 seconds)?

A quick check/solution would be to run a different line from your fuse block (from one of the accessory or "ACC" plug-ins that's not being used) to the coil. This will give you the full 12 volts to the coil in case you're not getting that now, which may be the reason the engine won't stay running.

might check fuel pressure. i'm just guessing, but if your regulating an electric fuel pump that is designed to pump about 14 psi, down to the i think 3-8 psi for carburators, you might have put to much stress on the fuel pump. it may not be putting out the 14 psi, there for, your not getting as much from the output side of the regulator.

Hello
I realize this is abouttwo months after your original post but..........
Your problem is that your fuel pump is not running....by that I mean that when you turn the key on a momentary relay powers your fuel pump, and once the engine is running your fuel pump gets powered via a different relay activated from the oil pressure sending unit to the computer. For a short answer you need a fused power wire to the fuel pump off the run side of your ignition switch.

Fedexjetmx is right on.

oh, another thing, I would think of investing a mechanical fuel pump for the engine, they are inexpensive...I put a 350 in my 89 toyota...used the existing electric fuel pump that ran at 40 psi...gas would occassionally boil out of carb do to blow by of the floats, (eventually this will prolly happen to you)...not good..trust me! so I pulled the relay for the fueld pump..just used the mechanical pump instead...runs great. my 2 cents.

toylet

I had that problem with one of my chevys and it ended up being a anti-theft device that allows the pump to prime the engine but does not keep on giving it fuel so the engine will start and run off of the fuel that was used to prime but when that runs out it dies