Somewhat successful start of the 70 vette
05-07-2002, 01:06 AM
#1
Somewhat successful start of the 70 vette I finally got to the point where I can start her up. I turned the key and the beautiful sound of an LS1 on open headers was heard for a 3 mile radius from my house. Ok, I maybe stretching it a little.
Well anyway, she started right up and ran for about 15 seconds and shut off. It did this several times which tells me I am not meeting the VAT device. I had built a VATs module to simulat the signal, but apparently it wasn't good enough. I am going to recheck my schematic to make sure I wired it all correctly.
Just to be sure, the '99 F-body uses the 5 volt, 50 Hz signal, right? If any of you have made your own VATs simulator, lets compare notes. I am sure it is something simple.
Well anyway, she started right up and ran for about 15 seconds and shut off. It did this several times which tells me I am not meeting the VAT device. I had built a VATs module to simulat the signal, but apparently it wasn't good enough. I am going to recheck my schematic to make sure I wired it all correctly.
Just to be sure, the '99 F-body uses the 5 volt, 50 Hz signal, right? If any of you have made your own VATs simulator, lets compare notes. I am sure it is something simple.
05-07-2002, 09:21 AM
#2
Re: Somewhat successful start of the 70 vette You're correct that the 99 F-body uses 5 volt 50 Hz VATS. If it runs 15 seconds each time, that's too long for a VATS turn off. I've never seen them go longer than a second or 2. Also, check your DTC's and see what's set. If its the first time to try and start it, you should probably clear the DTC's and see what resets. If it is VAT's, it will set a code. The 15 sec run time just seems a little strange.
__________________
91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
05-07-2002, 10:31 AM
#3
Re: Somewhat successful start of the 70 vette The reason I say it is the VATS is if I unplug the Vats simulator, it starts and runs exactly the same. It could have only been a few seconds, but with the adrenaline, it seemed like it ran for a while. How do I clear the DTCs?
<small>[ May 07, 2002, 10:41 AM: Message edited by: 70 LS1 ]</small>
<small>[ May 07, 2002, 10:41 AM: Message edited by: 70 LS1 ]</small>
05-07-2002, 11:24 AM
#4
Re: Somewhat successful start of the 70 vette Right now the power feed for the VATs simulator is wired from an ignition hot source. The only thing I can think of off the top of my head is maybe when I try to start, the voltage drops off just enough to not make the right signal. I am going to try wiring the power from the crank signal and see if that makes a difference.
05-07-2002, 03:23 PM
#5
Re: Somewhat successful start of the 70 vette You may need to find some sort of scan tool so you can see what's going on. That would also let you clear the codes. I think autotap is what many use.
__________________
91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
05-08-2002, 10:22 AM
#6
Re: Somewhat successful start of the 70 vette Ok, I think I figured it out. I checked my VATs simulator and it was only putting out 30Hz. That is out of the 40-60 Hz range. So off to Radio Shack to get some more coponents and rewire it.
05-08-2002, 10:34 AM
#7
Re: Somewhat successful start of the 70 vette Good. Hopefully that will do it. 30 Hz was the old Pass Key frequency. Maybe you built it to one of those earlier schematics. (Late 80's TPI).
Let us know how it works out.
Let us know how it works out.
__________________
91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
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05-09-2002, 12:26 AM
#9
Re: Somewhat successful start of the 70 vette I replaced the one resistor and it is now putting out 52 Hz. It started right up and roared to life. I finished all the wiring and now I have to hook up the clutch. Then on the the shakedown drive.
05-09-2002, 10:27 PM
#12
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Re: Somewhat successful start of the 70 vette Is there a write up anywhere about this trick? Where does the resistor get spliced into? I have a 94 Z28 I am putting an LS1 in and need to disable the VATS. I am using the 94 key. Any help would be greatly appreciated.
05-09-2002, 11:19 PM
#13
Re: Somewhat successful start of the 70 vette If I remember correctly, your 94 had an LT1 engine. The VATS signal is the same as the LS1. Now on the 99 that I used, the VATS signal was generated in the Body Control Module and sent to the PCM. If your 94 is the same way, you send the signal from the 94 BCM to the LS1 computer.
For me there was no one resistor that bypasses the VATS. I built a 5V 50Hz signal generator and wired it to the PCM. I made it about the size of a zippo and it is removable so I can take it with me.
If you need to build one, let me know. I still have the schematic.
For me there was no one resistor that bypasses the VATS. I built a 5V 50Hz signal generator and wired it to the PCM. I made it about the size of a zippo and it is removable so I can take it with me.
If you need to build one, let me know. I still have the schematic.
02-26-2007, 08:21 PM
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Originally Posted by 70 LS1
If I remember correctly, your 94 had an LT1 engine. The VATS signal is the same as the LS1. Now on the 99 that I used, the VATS signal was generated in the Body Control Module and sent to the PCM. If your 94 is the same way, you send the signal from the 94 BCM to the LS1 computer.
For me there was no one resistor that bypasses the VATS. I built a 5V 50Hz signal generator and wired it to the PCM. I made it about the size of a zippo and it is removable so I can take it with me.
If you need to build one, let me know. I still have the schematic.
For me there was no one resistor that bypasses the VATS. I built a 5V 50Hz signal generator and wired it to the PCM. I made it about the size of a zippo and it is removable so I can take it with me.
If you need to build one, let me know. I still have the schematic.
02-26-2007, 08:40 PM
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Glad someone brought this thread up. I bookmarked it for future reference. Thanks for working this one out and posting the outcome and fix of the problem Jeff. I will probably be calling on you for some help sometime down the road.
02-26-2007, 10:32 PM
#17
VATS schematic http://temp.corvetteforum.net/c3/70lt1/vats.shtml
This link and another link for a VATS bypass schematic are in the FAQ sticky post 13. https://ls1tech.com/forums/showpost....1&postcount=13
This link and another link for a VATS bypass schematic are in the FAQ sticky post 13. https://ls1tech.com/forums/showpost....1&postcount=13
