gaccett32

Im swapping in a 92 vette engine into my 92 bird, I can get the engine to start for a sec or two but it wont run, which I believe to be a VATS issue. I havent eleminated the vats in the ecm, and I was hoping to keep the vats by splicing my fuel enable wire from the vats module in my bird into the wiring harness of the vette ecm. But upon inspecting the entire wiring harness and the shcematics from the service manual I cannot find any fuel enable wire or other such vats to ecm wire to splice. Does the 92 vette not have a fuel enable, or is it some other wire with a different name that performs the same function. Or is it possible this is some other problem, I've been over everything else, vats seems to be the only possibility left, but I'm open to suggestions.

92LRC

doesn't sound like a VATS issue. VATS will not let the engine start at all. A 92 has a fuel enable relay but again this will keep the engine from starting at all and you're saying that yours starts then shut off.

Try this web site for more info on VATS and the wiring that goes with it.

http://www.vatssucks.com/

Good luck

Redeasysport

It's not VATs unless you swapped the CCM as well as the ECM but as posted it would not even start. VATS is in the CCM not ECM. Start with the basics check your fuel pressure.Air+fuel+spark= Ignition.I am not sure about how the serial data link between the ECM and CCM is handled in a situation like yours but trying to hook up your VATS to a Vette ECM is not going to work.I thin you might get better answers on a F-Body forum on what you are doing.

gaccett32

It has both fuel and spark, as it starts for second or two then dies and I've already checked those(but I'll recheck). I've been reading extensively on the all the vats info I can find including your suggested sight. The fbody forums all say its the vats and no one seems to know about vette wiring/ vat systems and suggested this site for specific info. Fbody lt1's have the fuel enable wire that can be spliced with a 3rd gen fuel enable wire which would resolve the vats issue but I cannot identify a similar wire in the vette wiring. From what I understand of the vats system the car will start for a second or two then die if there is a problem with the fuel enable signal to the ecm which controls the fuel injectors. AS the info section at vatssucks for 92-93 vettes says, there is a system for starting, and there is vats in the ecm, what does the vats in the ecm do/receive info from. It must do something to prevent the car from running. Like I said fbodies have the fuel enable signal from the vats module that simply tells the ecm that the key is correct and enables the fuel injectors. Is the vette system totally different?

92LRC

vats disables the fuel pump as well as the starter enable relay, the car never starts when vats is activated. althought they are both separate functions they are connected.

The fact that your car is running tells me, based only on what I know and this is opinion only, that your problem is not vats related. it doesn't even sound like the problem is starter enable relay related since it is starting.

my car has had both vats issues and starter enable relay issues. the car never started when I had that going on, not even for a sceond or two. I would just get nothing.

Sorry if this doesn't help but I really think that the problem lies elsewhere.

Keep us posted as to what you find. Good luck

Redeasysport

Like I said you are losing one of the big 3 which is air fuel or spark? We know it ain't air. Check your fuel pressure while it starts then put a timing light on if it is OK.

Also like I said VATS on A Vette is controled by the CCM not ECM. Look at the scematic on Vatssucks it will show it.It does show a BLK YEL 625 wire there that goes to the starter enable relay and you are starting it so that does not matter.

gaccett32

All the spark plugs are firing, all the fuel injectors have power, the fuel pump is pumping, and now it wont even start for a sec or two, it just cranks.

Redeasysport

Opti?

NEVRL8T

Its definetly not VATS.

gaccett32

New plugs, wires, cap and rotor, lifters, springs, BBK TB, comp 304 cam(which even the stock chip should handle), o2 sensors, and fuel pump. It has to be some ecm issue. When it started I could give it gas and it would rev good, then die as if the fuel injectors were cut off. I'm gonna get a few things tuned out of the chip and see if that makes a difference because I'm not running the vette vats, egr, or emissions.

gw962

Does the 92 system still have the CCM tied to the ECM for injector pulse? My 90 does, but I'm not sure what changed for the 92.

According to my FSM, the CCM first reads key resistance. If correct, it closes the starter relay and also and completes the circuit to the ECM fuel enable input.

Since you didn't change your 'Bird CCM, the signal from it to the vette ECM is not complete. This allows the car to start, but the ECM will not pulse the injectors. Pretty nifty back up.

Google Fiero Addiction. They sell a bypass module that plugs into the ECM for swaps like this.

gaccett32

That sounds exactly what I thought it was and what I was talking about. I didn't get the ccm with the engine and my bird still has its vats module. The service manual for the 92 doesnt have any wire that I can identify for the injector pulse enable except for a tan wire. I spliced my fuel enable into that wire and it didnt work. Maybe thats it and the signals are incompatible, if so I'm gonna have the vats in the chip disabled (and a few other things changed) so it won't matter anymore if that is the true problem. It defeintely seems as though the fuel injectors are not firing after the initial start up, which is what the fuel enable wire in the vats system is supposed to do, or at least all the info I could find has said about the vats for these years does.

gw962

If you're planning on haveing changes made to the chip anyways, that would be the best way to go. I have no idea how VATS works on birds, so I have no other advice. Good luck with the swap.

Redeasysport

I can't say for sure but I do not think you need the CCM to run the engine as long as you are able to get the fuel PUMP and starter working. That is what the VATS disables via the CCM. As far as I know it does not disable the injectors from firing.I believe the ECM is stand alone in function if the proper sensor inputs are gotten. You had it started. I am leaning toward the opti it is known to do exactly what has happened to you. Re check your spark pull a plug and ground it and turn the engine over see if you are getting a hot spark. Since you do not have the diagnostics(or do you have the ALDL hooked up?) and no SES light compatibility you will not be able to pull The DTC's from the ECM that might tell you why it is not working 2 of which are for the opti so you will have a hard time trying to figure out if it is the source without changing it.

schrade

Yup - not VATS.

2 seconds every time? (about)

Those 2 seconds might be runnin' on the rails primed fuel. After it cuts off, the PCM waits for distributor rpm signal to re-start the pump.

Just an idea...

gaccett32

I've checked all the plugs, all fired while cranking, the engine ran when it was pulled, and I swapped the cap and rotor. I really dont want to pull the opti now that the engine is in the bay, it was easy when the engine was out. It defintely seems like a fuel problem. It seems as though every other gm vats system at this time period had sent a signal to the ecm to enable the fuel injectors, is the vette the exception. Anyways I wont be able to work on it again until sat, and I'll be waiting for the chip and its subsequent results too. I don't trust any of the mechanics around my town($600 bucks for an est on my bros lt1 as a testament to that) to take it to for a second opinion on what could be causing the problem, short of the ecm. I dont have any aldl links attached yet as that was a low priority. Thanks to everyone for the help, I'll let you all know what happens next week.

Redeasysport

It is easy enough to verify the injectors get a Noid Light and put a pin into the harness to check for voltage. A VOM won't work as the pulses are too fast.

gw962

I'm only working off of my 90 FSM, but the fuel pump is NOT controlled by the CCM. Start Enable relay and a signal to the ECM to allow injector pulse are its functions.
Disclaimer, again.... this is from a 90 FSM. Fuel pump is hot, through the fuel pump relay, when the key is in the on position.

gaccett32

Made some progress, I can keep the car running if I rev it, but if I dont or try to maintain a constant rpm, it stalls. Still seems like a fuel problem, gonna get the noid light, I was just testing voltage on the injectors with a regular vom.

gaccett32

Did the noid test, the light goes bright on start then flashes erratically, I base lined on my bros injectors, which start weakly and rhythmically and then was brighter and stayed so. This must be the issue. But I wont have time till sat to work on it.