I can't find this info anywhere.

In a 1991 305 TPI, would VATS allow the motor crank but not fire up or would it not crank at all?

 

NOTHIN WOULD CRANK ,THATS HOW IT WAS WHEN MINE WENT

 

Its possible but unlikly for a vats problem to allow the car to crank. What are the symptoms that make you think its a vats problem?

 

Yes it would allow the engine to crank and not start if there was a problem with the signal at the ECM.

 

trickster knows all :hail: helped me many times

 

Thank you Sir Trickster and that is what I found this afternoon.

My problem is that it will run for awhile, and then cut out. After that, theres no starting until it cools down.

I was working with my mechanic and we let it idle, the most was 30 minutes until it just cut off and on another occation, it was about 5 minutes so it's totaly random. Not good on the highway.

Am I correct in assuming that if I use the resistor bypass, I would still have this problem bcause the ECM isn't getting the signal to energize the injectors and that it's most likely a bad VATS module or a short in the wire to the VATS?

Better yet, can I bypass VATS entirely?

Thanks all.

 

After the ECM receives the proper signal from the VATS, starter relay is enabled and ECM fires the injectors and the engine starts, then VATS is out of the picture unless you turn the engine off.

You can take the wire going to the ECM and.... oops... not supposed to talk about that here but there are ways around VATS without any resisters.

 

i don't think you are having a VATS problem. as far as i know your VATS works the same as my 92 setup does other than the fact i did away with the starter cutout relay on my car.
once the motor is running the ECM won't shut down the injectors because of a VATS problem. i have my VATS setup to where the ECM only sees the VATS signal when the starter is engaged, once im off the starter the VATS signal is no longer seen by the ECM. running it like i do, it does keep code 46 in memory but always starts with no problems.
what you want to look for when it won't start is fuel pressure, good fire from the ignition coil, & injector trigger.

*EDIT* also, with the key on check for power at the injectors during the no start.

SMasterson was alittle faster on the reply than me,.. said alittle different but the same point

 

You would be correct in assuming that you would still have the problem. I have included the ECM test for the VATS system. On your car, the wire to test would be the Dark blue wire going to pin L of connector C207 and from there it goes to pin "F10" of the ECM. And lastly, yes you can bypass the VATS entirely but not until you get this problem fixed. BTW, pin "F10" is the cranking fuel enable signal on the ECM.

 

page 2 BTW, I think what DENN_SHAH & SMasterson who posted above my two posts here are talking about is the INJECTOR drivers in the ECM failing.

 

We changed the ECM but the same thing happened.

My mechanics Snap-on scanner (too bad they're so damn expensive) also showed a VATS not OK after the car shut itself off but only twice.

Doesn't the VATS give the signal to enable the drivers?
And if there is a problem with VATS, couldn't it just as easily disable them?

DENN_SHAH had mentioned that once the car starts, the VATS is out of the picture. I just wanted to make sure so I checked the service manual.

It states that the ECM receives a square wave signal from the vats to enable the injector drivers but what I can't find is if it is constant.

Also, Trickster, where did you get those tests from? I couldn't find them in the service manual.

Thanks again everybody.

 

The tests are back in the wiring section of the manual along with the schematics of the Theft Deterent system section 8A-133.

 

Thanks!

 

Just an update because dead end posts stink.

I was in need of a ignition cylinder for about the past four years but since it never gave me a problem, I let it go.

Still not knowing for sure if the VATS module/ECM signal is constant, I changed my ignition cylinder. I also went to the dealer to see if they can find any info, other than whats in the service manual, on the passkey system.

My old key compared to my new key is night and day as far as the resistor and the old ignition cylinder contacts dont protrude as much as the new one does.

I still have a feeling that it's my module and I don't feel like taking everything apart and I really don't feel like dropping $225 for a new one.

Heres to hope.

Updates to follow.

 

Hello Scott,

Glad that you are running again. Did you get that service bulletin that I sent you?

 

Sure did, thanks

I will probably agree with you about the key being read while in the lock but how would you explain the motor being able to crank?

I drove it around a bit today and I'm going to test it a bit more tomorrow.

I was on the highway when it quit last time and I don't want that to happen again.

But thanks for all your help!

If your ever in NY, I'll buy you a beer

 

Well, a simple way to test it would be to try that trick I told you about with your second key and pull the wires while the engine is running and see what happens.