VAT system

[corvette66]

I have been fighting this no injector pulse situation, could it be the VAT system? The encoded key as I remember on my C4 has got to have somthing to do with this problem. Basically I took a stock harness from an 86 camaro and the whole tpi unit and put it on a truck. So if the VAT system prevents people from hot wiring a car..... my computer should never fire the injectors correct?

As I thought maybe I should buy a new stand alone harness, these companys always tell you the EPROM has to be reprogramed to remove the VAT.

If this is the problem how and to who do I send the PROM?

 

[vetteoz]

could it be the VAT system?
So if the VAT system prevents people from hot wiring a car..... my computer should never fire the injectors correct?

As I previously asked ;
what ECM and memcal are you using?

IIRC
86 F-Body should not have VATS but if you are using a Vette memcal in a '165 then it might have VATS enabled

 

[corvette66]

ECM is # 1227165
PROM # (on side) 16035006 8630 (on chip) 16055376 (sticker) delco AANK 1732

Sorry, 87' camaro not 86'

I'll just talk to you on this one, easier than switching back n fourth.

After reading that aticle, I'll try to check the TPS voltage.

Fuel pump situation... when the computer kicks the pump on for that initial 2 seconds, it goes to about 43 PSI but drops off to about 35 psi within 5 seconds, after about 2 minutes PSI is down to 25 and after 30 min the PSI drops to zero. Its a new pump so could it be that the regulator is letting it bleed through?

 

[vetteoz]

drops off to about 35 psi within 5 seconds, after about 2 minutes PSI is down to 25 and after 30 min the PSI drops to zero. ?

Not right but not your immediate problem.

If wired correctly ,pump will run again after oil pressure reaches 4 psi and the pressure switch operates the pump directly ( independent of the relay ) so if inj pulses are present engine should fire
( You have the oil pressure switch connected ? )

 

[vetteoz]

ECM is # 1227165
AANK

Could be your proiblem
AANK is a '86 Corvette auto memcal
First year GM installed VATS in any car.
Have you got another non VATS memcal to try ?
Alternative is to get a custom chip burnt with VATS disabled or buy the VATS simulator module to give correct signal to ECM

 

[corvette66]

The oil pressure switch is not hooked up only the pressure gauge (fat metal one) is hooked up. A guy on another post said it should run fine without it hooked up. I tried jumping a wire across it and naturally the pump kicked on.

So that PROM was NEVER used on an 87' camaro at all? No unfortunately I don't have another one. VAT's didnt show up on camaros till about 88 correct? AANK is for sure only an 86 vette prom? Any idea what a custom chip costs? It would probably be cheaper to find an 86 87 z28 prom huh?

 

[vetteoz]

AANK is for sure only an 86 vette prom?

Prom BCC 1986

 

[corvette66]

Chevy Thunder says 1986 350 5.7l so thats for sure a vette prom? There was no camaro with a 350 in 1986 I take it. Cool, well I talked to the guy who I got this stuff from and he failed to mention (until today) some of the parts were corvette parts but he couldnt remember what exactly. Must be the PROM.

How does it work? The key has a resitor in it that the VAT module reads and then what? The module sends a signal to the prom? No way to bypass it without the module huh? I didnt get the interior wiring harness only the main one.

A friend of mine had a similar problem. He got a new chip and the computer failed to read it. Is this an uncommon sitiuation? If I get a Used PROm I should be fine just so long as its not a vette prom and prior to 1988. can i use a 305 prom for a 350? The mass air flow corrects for that or not?

thanx, finally getting somewhere

 

[vetteoz]

Chevy Thunder says 1986 350 5.7l so thats for sure a vette prom? There was no camaro with a 350 in 1986 I take it.

You will note in those Prom listings F and Y in the last column
"Y Body " = Corvette
"F-Body" is Camaro /Firebird

How does it work?
The key has a resistor in it that the VAT module reads and then what? The module sends a signal to the prom?

Correct
VATS and PASSKey Vehicle Anti-Theft Systems - ThirdGen.org

VATS also enables a relay on the starter circuit ( not relevant to your setup )

No way to bypass it without the module huh?

Just buy this unit which simulates the signal needed to be seen by the ECM before it pulse the injectors.

http://www.bakerelectronix.com/products_vats/

cheaper than a VATS delete prom ($100)
Only requires + and - along with a wire to the fuel enable input terminal on the ECM

 

[corvette66]

Did not know corvettes where know as "y body" learn something new everyday

Baker electronics.... only $25 sweeeeeet!!!!!!

Do you know if they are reputable? Sounds like its just what I need.
Thanx for that info. super cool.

 

[corvette66]

I decided to get one of thoes Baker electronic VAT modules. So I put it on and still got nothing to the injectors. I only can think of a few more possible problems.

1. the Ignition control module might be bad
2. i dont have the cold start wire hooked up to 12v yet (not sure this would actually make any difference)
3. VSS wire is hangin loose. i have no vss
4. the gear select switch wire is also hanging loose, as i also have no switch

 

[vetteoz]

still got nothing to the injectors.
1. the Ignition control module might be bad

Have you got spark?

2. dont have the cold start wire hooked up
3. VSS wire is hangin loose. i have no vss
4. the gear select switch wire is also hanging loose,

None of those affect cranking injector pulse

Check the L98 start up link I posted for cranking / start procedure
Are both injector fuses good?

 

[boomdriver]

Have you got spark?


None of those affect cranking injector pulse

Check the L98 start up link I posted for cranking / start procedure
Are both injector fuses good?

I've been reading this with interest..
Does he have a FSM electrical book to reference?

A transplant harness and some parts .......fuse block, injector/ecm grounds, power supply from battery, fusable links, dozens of possible faults. Bank fired inj with no pulses..noid lite ??
Any distributer pulses to the ECM? Spark confirmed?
Whats been done about a center display so flash codes are accessable? nada? ALCL still intact?
Its real hard to chop a harness like this and use the pieces you want/need and discard the rest. The entire IP section has ECM/VATS related plug ins, relays, displays. To eliminate unwanted systems, lots of wire cutting and soldering/splicing to cut out plugs/modules to simplify the harness. Too much actually.

A call to Painless might have been worth the few hundred dollars for brand new brand new wiring...

I'd start with the drawing and see whats there and whats not. Begin with power and grounds to the ECM and work from there. Knowing there are seperate grounds on a vette harness for every item in the system,
the G-104 bundle could be missing and that one contains the ECM/FI grounds. No grnds, no zoom-zoom.
The key switch cable has to be jumpered with the right resistor,(unknown) the start-enable even with the cheap bypass module there still might be a "live" part of vats sending a signal, or lack of.
wow ! Quite a challenge !

 

[corvette66]

To start, i have an auxiliary fuse box and all fuses are good. If i spray carb cleaner in the engine it will run. But I'm not sure if this is spark coming from the computer or if it's somehow just working like an old one wire pickup truck.

No, unfortunatley I dont have the FSM book. Or a noid light, not sure where to get one. I dont yet have the ALDL hooked up yet or the check light. Without ever firing it up would it give me any trouble codes?

The cool thing is I have two harnesses. One on the vehicle and the other spread out on my work table. I've been going over this thing like a mad scientist. I'm to the point now where I may just get a painless system.

The vat module comes with 2 wires for different hz frequency, green wire 30hz and the newer 50hz blue wire. not sure which one mine is, I tried them both but still got nothing. It states in the instructions "30 hz VATS signal used on some 86-93 PCMs"

Another thing worth mentioning, my harness is from an 87 camaro that did not have VAT. So the plug location B6 did not have the wire for the VAT signal, it was an empty slot. To remedy this, I took a Pin out of the spare harness plug and added it to the good harness.

Well, i'm going to go look for grounds

 

[boomdriver]

To start, i have an auxiliary fuse box and all fuses are good. If i spray carb cleaner in the engine it will run. But I'm not sure if this is spark coming from the computer or if it's somehow just working like an old one wire pickup truck.

No, unfortunatley I dont have the FSM book. Or a noid light, not sure where to get one. I dont yet have the ALDL hooked up yet or the check light. Without ever firing it up would it give me any trouble codes?

The cool thing is I have two harnesses. One on the vehicle and the other spread out on my work table. I've been going over this thing like a mad scientist. I'm to the point now where I may just get a painless system.

The vat module comes with 2 wires for different hz frequency, green wire 30hz and the newer 50hz blue wire. not sure which one mine is, I tried them both but still got nothing. It states in the instructions "30 hz VATS signal used on some 86-93 PCMs"

Another thing worth mentioning, my harness is from an 87 camaro that did not have VAT. So the plug location B6 did not have the wire for the VAT signal, it was an empty slot. To remedy this, I took a Pin out of the spare harness plug and added it to the good harness.

Well, i'm going to go look for grounds

The ECM, if operating would still collect and store trouble codes. This was the first system with a memory that could do this.

The alcl might need to be in place since its an active port to the ECM.
One thing to always keep in mind on these harnesses....EVERYTHING operates on GROUND path completion, and power is always present. the grounds are used to turn on/off everything. Grounds are used to fire the inj as well. Power is everywhere...its almost like a positive-ground system but not, if that makes any sense...
There are 2 types of ground, grounds that are commons, to frame/earth, OR control grounds that operate everything.

Next would be the low voltage control or reference signals to some things...like MAF, a/c controls, ECM. 5 volts is the common reference from the ECM.

Look for 5 ground wires (blk) that will be coming out of the harness near the oil pressure wire. This G-104 bundle contains the ECM/INJ grounds that usually bolt to the block or bellhousing. I am almost positive the camero harness will be like the Vette harness because of the TPI requirements. It Might have less grounds being a steel body car, but the TPI on a camero still has the same engine mngt as the Corvette.

Without seeing what you;ve got, I can't guess at what the VATS status really is...2 wires? The Vats system has 15 variables for resistance....That key pellet has that many possible values. It completes a circuit in the switch, but if this was not a VATS harness and/or is a VATS ECM or prom...I dunno..
VATS is suspect because it cuts out the starter and the injectors. Starter bypass are common, so again...I dunno.

The fuse box is of concern....the stock box has certain things paired with others, and its not as simple as it would seem. If the aux box was wires the same way as the original, then its probably ok. There ARE other pathways that can interrupt the inj pulses other than the inj fuses. Csty fuse can cause VATS mishaps...

Use those links and drawings that Oz sent....he's the local genius and very good at diagnosing these cars. Maybe junkman will jump in.....but he's gonna tell you to fix the grounds before anything else!...and he's right.
The local parts store should have a GM noid lite. they're cheap...under $10 and very helpful to SEE when/if injectors are pulsing.

 

[vetteoz]

I can't guess at what the VATS status really is...2 wires? The Vats system has 15 variables for resistance....That key pellet has that many possible values. It completes a circuit in the switch, but if this was not a VATS harness and/or is a VATS ECM or prom...I dunno....

The VATS Bypass box he is using totally eliminates the key reader and VATS module by supplying the correct fuel enable signal direct ( that would have come from the VATS module if it read the correct key resistance ) to the ECM

As he states, GM used 2 different frequencies for this input; the bypass unit he has can supply either

He has a bit of a sh*t fight at the moment.
In these cases ( I just did a MAP retro fit recently ) I like to use known working parts and progressively swap in unknown parts to see if they work correctly.
Cuts down on the WTF factor

 

[boomdriver]

The VATS Bypass box he is using totally eliminates the key reader and VATS module by supplying the correct fuel enable signal direct ( that would have come from the VATS module if it read the correct key resistance ) to the ECM

As he states, GM used 2 different frequencies for this input; the bypass unit he has can supply either

He has a bit of a sh*t fight at the moment.
In these cases ( I just did a MAP retro fit recently ) I like to use known working parts and progressively swap in unknown parts to see if they work correctly.
Cuts down on the WTF factor

I hear that..
Thats why I was asking if the display was connected...to see if the ECM was even functioning. Then he could trace the missing inj pulses. Seeing the 12 code would be reassuring at this point !

These harnesses have so many sections that have to be right, that they're hard enough to deal with when they're on the original car. It's not at all like it was 30 yrs ago when we swapped engines or a harness in an afternoon.
.

 

[corvette66]

I hear that..
Thats why I was asking if the display was connected...to see if the ECM was even functioning. Then he could trace the missing inj pulses. Seeing the 12 code would be reassuring at this point !

These harnesses have so many sections that have to be right, that they're hard enough to deal with when they're on the original car. It's not at all like it was 30 yrs ago when we swapped engines or a harness in an afternoon.
.

Good call, I would like to see the code 12, maybe I'll install the ALDL tonight. I was just assumiong that the ECM was working bcause the fuel pump runs when the key is on, and once I start to crank the engine the pump then runs again after a few seconds.

 

[vetteoz]

once I start to crank the engine the pump then runs again after a few seconds.

Do you have the oil pressure switch connected?
if so pump will run off that feed directly with out any input from ECM
As per the L98 Start up procedure ; the ECM needs to see dist ref pulse required to pulse injectors and run pump relay again

Having access to the codes is the only thing that is going to give you an idea where problem(s) lie

 

[corvette66]

The pressure switch is not hooked up yet. So if the pump kicks back on after cranking, I can assume the ignition module in the dist is OK then? If I'm reading that correct... the ecm is seeing the ref pulse and kicking the pump on.

About the ALDL, I have one from an old 93' s10. it has 5 wires going to it. I'm planning on using this ALDL link for the TPI. I'm looking at the info on chevythunder and it seems as if the ALDL on the TPI should have 8 wires or maybe 5 wires. On the schematics I see on the main harness plug 5 go to the ALDL but then when I look at the ALDL schematic it shows that there are 8 wires coming from it. Does this sound correct? Also if I do get the ALDL plug wired up, where do I hook the wire from the check engine light into?