PCM / wiring problem

[69camarokid]

so i have a 69 camaro with a 95 Trans Am LT1/t56 in it.

The computer was tuned by Brian from PCM4less.

When the cars ignition is in the starter on position the car will start. But when the key flips back to the power on position, after the starter has started, the engine will shut off.

I took it to my auto electrical shop and they said the car is losing power in the white power wire from the PCM to the ignition module when the key goes form starter position to power on position.

:hmm:

Im being told its not a wiring problem, but that its a compter tuning problem. I talked to brian from PCms and he said he doesnt think its a tuning problem. im stumped. anyone have a problem like this? any ideas would be a great help!!!!!

[demonpixel]

camarokid, make sure the wires from your ignition module are large enough. electricity needs to flow well enough through wire and i've had electrical problems that went away when i went a larger gauge. better to be too big than too small.

what i would do also, imho, is check the mechanics of the ignition module. maybe try a $10 push button starter and see if you get the same problem. if you do, it's probably not the ignition switch.

i've been following your build man. beautiful car; i know you'll get this thing running.

[Bow Tie 67]

It sounds like a wiring problem and the ignition switch is not properly wired into the new electrical system. You'll have to research the 95 engine start / run wiring schematics and see how the original ignition switch was wired in. Then make sure the 69's ignition switch run position is suppling power to the same circuits as the 95's ign switch in the run position. If that is correct then you may have other problems.

[Bow Tie 67]

crap double post.

[matty b]

any news on what pin isnt getting proper power? there is a good chance that your igition switch doesnt have a buit in by pass leg in the start position. If this is in fact the case then you can build a relay onto the ignition switch wiring so that the pink wire stays hot in start if it doesnt already. To do that wire a bosch relay as so...
1. splice of of the battery lead (10 gauge red) and connect it to pin 87 on the relay.
2. Splice into the pink wire on the igniton switch and hook it to pin 30.
3. splice off of the purple wire (start lead) and hook it to pin 86
4. hook pin 85 up to ground.
what this will do is applie power to the ignition circuit in the start position. The relay is triggered by the start leg and the igntion circuit is powered by the battery lead. I had to do this on a 1960 pickup truck but have never ran into that problem on your model of car. Try it out it wont hurt anything if you do.

[69camarokid]

the car is at my mechanics shop, so im unsure as to which pin the wire goes to. All i know is that its a white wire that the GM wiring specs says goes from the PCm directly to he Ignition module. I will print out what youi said though and take it over and see what i can find out.

thanks again to everyone for the advice and help. it really is appriciated!

[SSTuner]

Did you have "VATS Select" disabled when you had the tune done by Brian?

[SSTuner]

More info.

Copied from another link:

What VATS does, it outputs a 50 hertz signal to the ECM so it can turn on the "injectors" and the "fuel pump enable relay" also it sends out a signal the "starter enable relay" so the engine can crank . It works with the pellet resistence in the key.

I just did a 383 LT1/T-56 in my sons 1987 Monte Carlo SS and all we did was disable VATS with Tunercat. No need to buy one of those fancy VATS bypass modules.

[Bow Tie 67]

With VATS enabled the car won't turn over or start, his does both.


More info.

Copied from another link:

What VATS does, it outputs a 50 hertz signal to the ECM so it can turn on the "injectors" and the "fuel pump enable relay" also it sends out a signal the "starter enable relay" so the engine can crank . It works with the pellet resistence in the key.

I just did a 383 LT1/T-56 in my sons 1987 Monte Carlo SS and all we did was disable VATS with Tunercat. No need to buy one of those fancy VATS bypass modules.

[HILROD]

That's not true, depending upon what year it is, Vats can disable cranking, ignition, or fuel, one, or all.

[69camarokid]

the engine is from a 95 trans am.

well with a little more inspection it turns out for sure that the ignition wire has power to the pcm while cranking, but upon start up the pcm stops sending the signal, which is, according to the GM wiring schamatics, supposed to send the signal to the other half of the brain, nad from there to the ignition module.

my mechanic thinks he found a way around it with some help from some people on this forum, so thanks guys. hopefully it wil be up and running in a few days.

[SSTuner]

Any status?

[69TA]

Ive followed your thread on your 69' Camaro. Nice job, I also am tight on $$ and have been working on a 69 T/A clone that I installed a 94' LT1 in... I have it all wired up and everything *should* work.

I think I have the same problem with VATS that people are talking about. I just installed a 94' LT1 and have EVERYTHING wired up to work through the PCM except starting it.(fuel pump, fans, etc..) I havnt done anything with my PCM yet and my PCM isnt doing anything yet I know its getting power and everything should be grounded good. It wont even allow my fuel pump to prime. I have a guy disabling vats and tuning my PCM tomorrow so we'll see what happens. Your thread on your camaro has helped me alot during my build. :cheers:
Hopefully I wont have the problems you are having now after I get it running, but Ill find out!! Keep us updated!