VATS trouble!!!

Hello all, I'm new here, but I come to AF all the time to research problems for other people. This place always has the answer. I hope you have the answer this time. :smile:

I have an 87 GTA. I swapped in an L98 (5.7 tpi), a 700r4 and ecm/harness from an 89 Formula 350. Everything is stock. I have a VATS bypass module installed to eliminate VATS.

The engine will not start up after dozens of failed attempts because I have no injector pulse. I have good spark, fuel pump priming for 2 seconds, good cranking, fuel all the way up to the schrader valve, and 45 psi FP. Nothing else seems to be out of the ordinary... except maybe these few things.

1) I have 11.5V at both pins on all 8 injector plugs. I don't know if this is the way it should be or not.
2) I also have 4.99V at the VATS wire B6 (ECM) or pin L (C207). I don't know if I should have voltage there either. I thought only a 30hz frequency was supposed to be present on this circuit.
3) While checking the injector harness with my test light, I accidently let the wires cross. The bulb dimmly lit, and there was a buzzing noise. Could this have caused problems with my ECM? How can I check to see if I have a bad ECM? My SES light still comes on and it flashes 12 like it should.
4) It may be coincidental, because I don't remember if this happened before, or after I let the wires cross... The VATS bypass module has an LED on it to show it is functioning. AFter the wires crossed it would only be bright for a brief moment after I turn the key to run then get dim (probably because there is 4.99 volts on blue VATS wire???). Then when I disconnected the module form the blus wire, the light got so dim, I couldn't hardly see it anymore. It is VERY dim.

Any suggestions on what to do to get my car running?

if the car is cranking but not starting, the VATS is not the problem. VATS will keep it from cranking completely.

Spray some ether into the throttle body and crank it over, if it fires, you have a fuel delivery problem. If it doesn't fire off the ether, you have no/weak spark.

Since you already stated that you have good spark, you probably have the fuel delivery problem. One possibility is the oil pressure sending unit went bad. I had this same problem last year. You see, the system is set up to where if the oil pressure drops, the fuel pump will shut down to prevent damage to the engine. It will still prime with ignition on, but will not run while cranking and after. In my situation the sending unit still showed oil pressure on the gauge, but didn't send the signal to the fuel pump to run. I tested this by checking for voltage at the wires coming from the sending unit while a friend cranked the car over.

I hope this is of some help to you.

if the car is cranking but not starting, the VATS is not the problem. VATS will keep it from cranking completely.

Spray some ether into the throttle body and crank it over, if it fires, you have a fuel delivery problem. If it doesn't fire off the ether, you have no/weak spark.

Since you already stated that you have good spark, you probably have the fuel delivery problem. One possibility is the oil pressure sending unit went bad. I had this same problem last year. You see, the system is set up to where if the oil pressure drops, the fuel pump will shut down to prevent damage to the engine. It will still prime with ignition on, but will not run while cranking and after. In my situation the sending unit still showed oil pressure on the gauge, but didn't send the signal to the fuel pump to run. I tested this by checking for voltage at the wires coming from the sending unit while a friend cranked the car over.

I hope this is of some help to you.

I will check for power at the fuel pump while cranking, but I still don't have injector pulse, and I should. I need to figure out why, because the injectors will not run without this. I have sprayed etehr into the TB and the car fires off fine.

However, the only part of the VATS system that is left is the program burned into the PROM. My 87 GTA did not come with VATS. This car was designed without it, so there should be nothing stopping it from cranking the engine. If this was my 89, then yes, I would look elsewhere for the problem.

I had to buy a VATS bypass module to trick the ECM into thinking the BCM (body control module) of the VATS system is sending the 30hz signal to the PROM to turn off VATS. Once the signal is received by the ECM it will then allow my injectors to receive the power they need. This is exactly what the Vats system does.

SOOOO... since I don't have injector pulse, I can only assume for now that the bypass module is not sending the necessary 30hz needed to turn VATS off in the PROM.

As far as the oil pressure sender goes, doesn't the ECM run the pump once it see refernece pulses from the distributor?

This engine run flawlessly in my 89 Formula. I just swapped everything over. Hmmmm.... Thanks ALOT for the help. Keep it coming. Talking and thinking it through is what gets my brain going. You're helping me more than you know.

i forgot to take into consideration that the ecm you're using isn't the original, and has differences. if you were to just plug in an 87 L98 ecm, i bet it would fire right up and you wouldn't have to chase this problem down.

I'm sure that's not what you'd want to do, but I'll just throw that out there as an option.

I'll let you know if I can think of something else.

i forgot to take into consideration that the ecm you're using isn't the original, and has differences. if you were to just plug in an 87 L98 ecm, i bet it would fire right up and you wouldn't have to chase this problem down.

I'm sure that's not what you'd want to do, but I'll just throw that out there as an option.

I'll let you know if I can think of something else.


I think you're right, and I would definately do that. I don't have one though. I also would rather not spend the money, but I might have to. Do you have one? an 88 ECM will work too. I wish I knew someone who had one that I could borrow, but no onw I know has one.

I have 11V at the fuel pump while cranking by the way. I just don't see why there would be 5 volts on the VATS wire. :shakehead

if it starts with starting fluid it's not getting gas up to throttle body. have you changed gas filter latley. and on that vats system theres a little white wire running down beside sterring colum and they brake easy what they did is put a small wire instead of thicker one so you would have to take it to a mccantic..hope this helps you..

if it starts with starting fluid it's not getting gas up to throttle body. have you changed gas filter latley. and on that vats system theres a little white wire running down beside sterring colum and they brake easy what they did is put a small wire instead of thicker one so you would have to take it to a mccantic..hope this helps you..

Thank you for the reply. I know that I have a fuel delivery problem. I am not getting injector pulse. The injectors are not receiving the pulse to fire from the ECM. Also, my car does not have VATS. I am using an ECM with VATS in it in a car that never had VATS installed from the factory, so there are no VATS wires other than the VATS wire on the 89 ECM harness.

By the way so everyone knows. This combo was running great in my other car. New fuel pump, filter, injectors, plugs, wires, cap rotor. I just need injector pulse.

Does anyone know...
1) if I am supposed to have 11+VDC at the injector plugs?

2)if I am supposed to have 5VDC at the Blue VATS wire going to the ECM?

3) How do I test for the 30hz that is supposed to be coming out of the bypass module. This way I will know if the bypass module is still working.

Thanks alot.

Oh one more thing, if anyone has a 86-88 ECM with PROM for a TPI 5.7 liter, please let me know. I'd like to buy it.
Travis

12 VDC on both injector terminals is normal. The ECM switches one of them to ground to fire the injector(s).
5 VDC on the VATS is normal.
You mentioned noid lights..I take it they are NOT flashing while cranking?
And IF the engine cranks over it is NOT VATS related. VATS only disables the starter.
If you are not firing the injectors, look for a bad ignition module. the ECM gets a refrence pulse from the distributor and when it sees it, it will fire the injectors.
If the module is good, look at the ref pulse wire from the distributor to the ECM.

It is possible that when you crossed the wires you burned up a quad driver in the ECM too.

This might help:

http://mysite.verizon.net/strey/files/VATSSystem.html