A little while ago i posted on this forums about how i was doing an engine swap. I was swapping a 3.4 to a 3.8 and from automatic to a 5 speed. so far we have got the engine in and hooked up (along with the 5 speed) and all the electronics and we can get the car to turn over (and even get spark) but it just wont fire. We found a primer line to the fuel pump and hooked that up to the battery and then tried starting it and it still wouldnt fire. the security light comes on, but it still cranks over. Im thinking the problem is something that has to do with the BCM. Its really starting to get me frustrated. Any input would be nice.

 

Anybody have an idea? I was also told it may not be the VATS. maybe a sensor. one proble it may have is the firing order going to affect this? I think the 3.4 and the 3.8s had different firing orders. Gorn i know you probably know something, cause you saw this coming.

 

yah gorn whats up? lol.

 

Did you change the PCM? 3.8 & 3.4 have different sensors & PCM. The 94 car does not use a BCM. The firing order is different: 3.4=1-2-3-4-5-6, 3.8=1-6-5-4-3-2.

 

Since you used the Harness and the PCM from the 96 I would think the firing order would not be the issue. I know the VATs system needs something. If it even sees the new PCM it would know its not the same Vin. The thing I have no clue about is how the 96 PCM is reacting to all the none 96 systems it is seeing or its looking for systems that are not there. All it would take on one wire on one connector to be pinned differently and everything would shut down or worse fry the system. There may be someone out there with the know how to do this. It aint me. I just know enough to know that the chances it would be plug and play where pretty slim.

 

heres a link to a video that may help you guys get a visual.

http://www.youtube.com/watch?v=yGLpSM6YirM

 

The VATS prevents cranking and shuts down the fuel injection. It does not shur down the spark. The system consists of the special key with resistor pallets, a VATS module under the dash which reads the resistance of the resistor pellet, and if it is correct it will signal the PCM that all is OK. If all is OK then the PCM activates the stater relay which then energizes the starter solenoid, at the same time it will allow the injectors to fire.
Since the engine cranks the VATS is "probably" OK. You may want to verify this with some NOID lights and see if the injectors are being pulsed.

I seem to remember (although not positive) that a VATS module will only mate up to the PCM only once, so if it is mated to the original PCM you may have to replace it wit a new one, need to do some more research on this.

 

Well, if its cranking it has compression...you have spark, and you've added fuel, so it SHOULD run.

Im not sure of the best way to verify the firing order is correct but I doubt its the BCM. When I have a VATS issue the car will not crank.

 

You sure your fuel injectors aren't plugged? I would unbolt your fuel rail and crank it over just for a moment to make sure you're getting fuel out of them (there's probably an easier way to verify this but I don't know it).