I'm coming down the home-stretch with my LT1 swap, but have run into a snag. I have the vats bypass module hooked up to my 94 lt1 computer, but I think the original vats in my 89 gta may be killing my fuel pump... It's obvious that there is a problem with the vats on my car since the starter enable relay needs to be jumped in order to crank the engine. My question is whether or not the car's vats is still able to kill the fuel pump even though it's being run by the lt1 computer. My fuel pump primes, i have pulse and spark but the engine just pops as it cranks. It does run off spray.

 

pin A25 in the red PCM connector of the LT1 is the Fuel Enable signal. It has a square wave frequency on it when everything is good to tell the PCM that the VATS is good. Your car wouldn't work without this except that you bypassed the vats .. I'm not familiar with the bypass module but it must wire into this or you have programmed the VATS out of the PCM.
http://shbox.com/1/pass_key.jpg

 

Thank you for the reply. It turned out that my problem was with air not fuel. My IAC is apparently not functioning and is either no good or there is a small chance I may have somehow mixed the IAC coil "A" low lt blu/blk wire with the brake switch signal wire that shares the same color, in the same connector. It may just need to be reset. Monday is my day off/work on car day, so I hope to have it all sorted tomorrow.