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LT1 dies at start up Posted By: 69LT1C10 On: 06-18-2009 @ 15:43:40 Reply | Edit Hi all!! I am looking for a little help here and I hope someone here is able to help me because I am about to pull my hair out on this thing. I have a 1996 LT1 that was removed from a Chevy Caprice. I have it in my project vehicle and have everything temporarily in place. By everything, I mean fuel system, radiator, fuse block and PCM. I haven't permanently mounted anything yet because I am not sure yet where I will want everything after the engine is running properly. Anyways, the problem I am having is that when I go to start the engine, it will run for about 1-2 seconds and then just die. I have read every post I could find on the internet about this issue and they point to several things. First is the VATS system. It is my understanding (correct me please if I am wrong) that the VATS will not allow the fuel pump to continue operating if the incorrect resistance is found coming from the key chip. I had thought I solved this problem when I began by just bypassing the computers fuel enable signal by putting my fuel pump (aftermarket MSD external pump) on a toggle switch temporarily. This actually allowed the engine to start and run beautifully for about 2 seconds (LOL). I have replaced the fuel pressure regulator today because I didn't have any pressure at the fitting on the line after priming the pump. There was only pressure when the pump was actually running. Now I have pressure for several hours after the pump is primed and the rails are energized. I have tested the coil and the ignition control module and everything seems ok. When I fire it up, it just seems to stop like the plug was pulled on the coil or something. Any ideas?? Am I wrong about the VATS thing, does it cut off the injectors too?? Or just the fuel pump signal? PLEASE HELP ME! LOL!! Posted By: Green97TAMachine On: 06-18-2009 @ 23:40:31 Reply | Top | Edit The motor will not even turn over if it is a VATS problem. It sounds like a bad MAF sensor may be your problem. Do you have it hooked up and in place on the intake tube? If so, try unplugging it and see if anything changes. -- 
1997 Mystic Teal Trans Am Best Time: 13.984@102.99Mph  Posted By: 69LT1C10 On: 06-19-2009 @ 06:24:00 Reply | Top | Edit Actually, the motor will turn over if it is a VATS problem in this case. The vehicle is a 1969 so the starter is wired directly to the 1969 harness and doesn't need the computer to physically turn the motor over. And yes, the MAF is plugged in as well as the MAP and starting it has been attempted with them plugged in and unplugged, still starts and dies. I am really beginning to lean towards the VATS thing. I read some stuff last night that said the computer shuts down the injectors if it doesn't get the correct signal from the VATS module. In the original car the motor was in, this would never be noticed, because the engine would not even turn over if the correct value was not given to the computer. In my case, I am running a fuel pump by toggle. This sends fuel to the rail. Then the computer sends a prime pulse to the injectors when I turn the ignition to the accessory position. This allows the engine to fire and turn over and get enough fuel in the cylinders to run for about one second. Originally I thought the computer just shut the fuel pump down because of the VATS, and I thought I had that fixed by toggle switching the fuel pump, but it seems now that I may have been mistaken, and it may actually be shutting down the injectors. I have someone at a dealership here that owes me a favor. He said he would program out the VATS for me. But I need to get an OBD2 diagnostic port installed so they have somewhere to plug in. Looks like I need to head to the junk yard today and see what I can find. Then I gotta figure out how I am going to get it down there. LOL. Thanks for the reply, and if anyone else has any info on the VATS to let me know if my assumption is correct, I would appreciate it.
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