I have a Third Gen LT1 engine swap that is almost complete. Everything has gone well (and this is my third fuel injection swap on three different cars so I have some limited experience) until I start the engine. It started on the first attempt without any problems but will only stay running about 10 seconds until it shuts down like you have turned the key off. Some of the things I have checked are -

1. The battery is new and well charged and will start the engine each time.
2. The fuel pressure is about 44 psi before it starts and it about 42 psi once the engine is running. The fuel pump is a brand new Welpro.
3. The fuel pressure will remain about 40 psi for about 10 minutes or longer after the engine shuts off.
4. The oil pressure is approximately 45 psi (at the rear engine outlet) during cranking and is about 70 psi when the engine is running (cold). The engine was completely gone through prior to install.
5. The wiring has been checked and rechecked and the grounds all appear to be good. One is connected to the intake manifold right behind and at the side of the throttle body, another on the side of the passenger side head, and the third at the block at the starter.
6. There are two body grounds to the engine. One is from the frame near the motor mount directly to the block, the second is from the battery to the frame.
7. The battery “hot” is directly to the starter.
8. The alternator output is directly to the starter post where the battery hot connects.
9. With the engine off, there is 12.6 volts at the alternator post and starter and across the battery.
10. I cannot check the alternator output with the engine running because it will not stay running long enough (there is only one of me) but it worked correctly before the install.
11. The exhaust is not hooked up yet so the exhaust dumps directly below the exhaust manifolds (but does cross the oxygen sensors).
12. I can’t read the trouble codes (if there are any) because I don’t have a SES light hooked up yet or have a scanner. I am still trying to figure out how to best do that. (Suggestions?)
13. VATS was supposed to be removed from the computer.

Anything you can do to point me in the right direction would be appreciated.

 

Sounds like VATS. Like you said the fuel pressure is still high when it shuts down so the fuel pump is being cammanded on. I would try and hook up a noid like to the injectors, you might be able to see the light stop blinking slightly before the engine dies. This would prabably indicate that the VATS was not taken care of.

 

Sounds exactly like what VATs does, an injector noid will help, and if thats not simple to get ahold of, i use a 12v mini bulb.

 

I will try to find a noid light but tomorrow I will use the 12v mini bulb. Thanks for the help and I will report back.

 

What year car is the swap in? Connecting the MIL and ALDL should be considered mandatory for the swap to speed troubleshooting issues like this

 

I get your point. This is an aftermarket stand alone harness that is going into a '89 so I am not interfacing with anything original in the car. In my urgency to get the engine running, I have not wired either/or.

 

Yeah, sounds like VATS as well, doesn't change anything on the injectors, but VATS on an LT1 turns the fuel pump off and it will act just like turning the key off. If you turn the key off and back on, it should fire up and run for about 5-10 sec then turn back off again. If you try to start it before turning the key off it will act like it doesn't have enough fuel to start.