after tons of research, I have finally decided to break down and just ask the question myself for my personal situation. I have an lt1 out of a 94 camaro with the wiring harness and computer out of the same car. The car does start, but only runs for a few seconds and it does not start every time. I have spark, I have tested the resistance on each of my injectors. I do have a vats bypass module wired in for 50hz. My next test is going to be getting a noid tester and checking signal at each injector. Here are something that are still confusing me though:
-The car wont start everytime, but it does start
-Usually it runs for about 3 seconds, but it did run for about 10 seconds once
-Sometimes I can hit the throttle in that time to rev it up, other times I hit the throttle and it just stalls (maybe just coincidentally when it was about it stall anyway, I'm not sure)
-I have the pump running off a 12v source with a toggle switch because i tried using a relay and wiring it multiple different ways and no way did it ever run the pump with the relay
-Thinking it may be a vats problem, I tried starting without the bypass module and it did the same thing. Does vats kill spark and the injectors or just the pump? (If my module is faulty and vats just kills the pump, that would explain why the pump never ran off the relay, but wouldnt explain then why the car only runs for a few seconds

Any insight on this problem would be great, I cant imagine that I'm the only one that has ever had this problem with all of these same conditions

Also, fuel pressure seems to drop very quick after the pump is shut off instead of keeping pressure in the rail

have you gotten your pcm tuned?

no, its just a stock motor with a stock pcm. i havent had vats programmed out because i bought the bypass module

I just read that vats does control the fuel injectors, does anyone know if this is true or not? and if it is, wouldnt the engine not start at all if it was a vats problem?

Witch bypass module did you buy? I bought the one from ebay and it's works perfect.

You don't have your module hooked up right if it runs for 5 seconds and then shuts down. That's a sign vats is shutting her down.

http://www.ebay.com/itm/GM-VATS-PASS...item4167069889

This one works as should.

well my vats wont let the car fire at all. it locks the injectors and doesnt allow the starter to fire the motor, it just turns the flywheel. it suggest tuning it instead of bypassing it. not that bypassing it wont work but the tune can disable emmisions, number of O2 sensors, they can even retard the timing for better fuel economy.

Yeah getting it tuned out is the best bet but for 14$ it does what it should. vats will let the injectors fire for 3-5 seconds, all this does is trick the pcm to give vats a 50hz signal every time you turn the key on. It's a pretty brilliant piece.

Vats on a thirdgen started in 1985 disables starter enable relay that's probably what your thinking of witch you can bypass by taking the left kick panel off the driver side and there is this sticky black rubber piece, take it off and there will be a large green, yellow wires you cross together. Your starter will now work cprmn.

cool man thanks for the advise!

My camaro is an 83 and has no vats. I have the ebay bypass module wired in as instructed. Swithed 12v to the red wire, signal wired to the fuel enable, and grounded the white wire and ground

did you have the vats tuned out of your ECM?

vats isnt hard to bypass and you dont have to have it tuned out of the pcm unless you really dont like doing some simple wiring.Also dont need to buy the ebay module to bypass vats..gm in the infinite wisdom only had a handful of vats resistances,buy a vats resistor pack and spending 5 mins trying out the individual resistors untill the car started is how us installers had to figure it out if the original key lost its pellet.Some cars had starter relay cutoff tied in with vats which is a simple bypass in the kick panel as mentioned above.As for fuel..the pcm will always prime the system,you could crank the motor over and it would start and run for 3-5 seconds using up the fuel from the initial prime.If the vats signal isnt the correct value during crank then the pcm will not command the fuel pump on.later versions of vats..mostly 90+ I believe would also control fuel injector pulse to further secure the car from starting without the correct resistance.

the pcm only needs to see this proper value during crank,once it does..you could take the resistor off the vats wire with the car running and it wont shut the engine off.Its just a security measure during crank and if it is the right one..it only checks during crank cycle.Also on some of the last versions of vats if the improper resistance value is seen by the pcm 3 times in a row it would go into a security mode for a period of 10-15mins and lock itself up from doing anything.This gave gm many manyy problems and compliants during the 90s with ppl stuck in places because the worn out key on hot days would read a different value and bam..no start!

Aside from that I see you mentioned that the fuel pressure in the rail dies off pretty quick after its been primed? That is a mechanical issue to look at now,you will have a fuel system failure somewhere.If you have a fuel pressure gauge and can manually prime the fuel pump for 2 seconds.The pressure should hold for quite sometime before starting to bleed off....I mean over 30mins sometimes before it drops.If this drops to 0 right after the pump turns out.you have a big leak in the system..or leaking injectors.This will require some trial n error testing and process of elimination.Fix this now before the vats issue and scratching your head as to why it wont run properly even after vats is fixed and confuse you more.Looking for weak pump,bad fuel regulator,stuck open injectors.

Hope this helps.

Thanks, i will look into the fuel problem before going further into a vats investigation. The vats really shouldnt be a problem with the bypass module wired in. I know my fuel lines are not leaking and i have a brand new pump and i have tested power right at the pump. Is there anyway to check for leaky or stuck injectors without pulling the fuel rail off?

what kind of pump is it? it could be faulty. first i would check fuel pressure at the rail. it should be around 60lbs or so. and crank it to see if you loose pressure. If that checks out then you can move forward to the injectors

Im running the stock tpi fuel pump. That should keep up with it, right? Even if its just enough to get it running. So you're saying that the rail should hold about 60 psi and should drop while cranking? If so, what should it drop to? I read that running it should be about 42 psi?

Thank you everybody of the thirdgen community. My problem has been resolved. It ended up being a problem with the sending unit. My camaro has now been from burned up in a car fire to a sucessful lt1 swap in just 6 months. Body and paint, here i come

Glad to hear its up and running,post some pics/vids

agreed on the vids! and congrats man

Mines doing the same.thing.i had the computer flashed also , did you.replace the pump or the whole unit?