No start condition

[Fbody383]

Check and recheck the whole vats circuit.... that system is a real pain. I bought the vats bypass to avoid that crap after I had trouble.

I thought the VATS was in the anti-theft system and in the factory wiring migh shut off fuel pump and definitely shut down injector firing but NOT in the start circuit.

Motor not continuing to run I would lean towards VATS, but no starter turn over makes me think anti-theft relay.

Find the starter relay in the interior wiring. Of the top of my head I think the heavy purple wire goes to the starter solenoid. Check voltages at that relay socket.

[NickV]

The gas tank is still out of the car....does it need a signal from the fuel pump?

When we put the Painless harness in my car, there was a signal wire that we hooked up to a +12v source to trick it in to thinking the fuel pump was on (because I have my fuel pump on a separate switch), or else it wouldn't start.

When we had VATS issues, the motor would at least try to turn over, but never start.

[Casey_SS]

And the saga continues.....tried pulling the tune off the PCM to edit VATS out and it can't get a response from the PCM. Looking through schematics to figure out which wire supplies PCM power to test to see if it's getting power....

Just tested all the harness grounds I'm aware of and they all show 0 - .2 ohms to the battery ground. I tested the one near the steering column, two near the driver seat, and one near the glove box. Are there others?

Only things not connected are what went to the door harnesses and headlight switch / dimmer.

I know the harness is getting power because I have idiot lights and I know the BCM is working because my daytime running lights come on when I turn the key on (light sensor is buried in a dark place).

What am I missing?

[GlennCMC70]

OBDII port gets power from the lighter or seat circuit. Check for 12V at the OBDII port.

Also look at the connections James mentioned at the column.
You also need to check the start relay. Check to see if your getting the command for the relay to close (small wires - one is ground and one is power to the relay) and that 12v is coming into the relay (purple wire) and out of it if it is closing. I remember there being a weatherpack for just that purple wire under the hood behind the PCM.

So, check that the start relay is clicking, if not, find out why. If it is, the computer is not the issue, but power to or from the relay is. You must start here so we/you can tell where to start next. This will isolate the problem to computer/signal or relay/power.

A test light is good for this type of troubleshooting. Make one from a 12v bulb if you dont have one. I use an old license plate lamp w/ long leads on it w/ aligator clips on the end. place it in line of sight to see if you get a go/no go indication.

[Casey_SS]

OBDII port has 12.4 volts. PCM has 12.3 volts. I don't have a single purple wire coming out behind the PCM but I do have a rather large (10-12ga?) purple wire in one of the harnesses coming out in that area. It goes down towards the starter so I'm assuming that's the one. If so, it does not appear to be getting power when I turn the switch to "start".

Not sure where to go next except pull the dash back off and go digging around the column and hope I find something. Gonna eat first, drink a beer, and hide all the dammit tools before proceeding further.

[Casey_SS]

One more thought - back to basics. The only things I changed on the car are as follows:
Battery moved to trunk
2ga wire from + battery to master disconnect
2ga wire from - battery to rear frame rail
2ga wire from disconnect to bulkhead to stock + battery cable going to starter
Stock - battery cable goes to stock ground point near junction box (grounds engine to body)
Alternator & junction box wires originally on stock + battery cable go to bulkhead
16ga wire interrupts + wire on ign. coil via disconnect
Removed door / cross body section of harness
Pulled HVAC, Airbag, wiper/wash, radio accy , courtesy, defog, windows, & radio fuses

That's all that changed from "known good"....anything suspicious here?

BTW - Glenn - there's a relay under the dash with a big purple wire going to it that DOES click when I turn the key to start. Not sure why it's not showing power downstream...no visible problems in the path.

[mitchntx]

OK REAL basic ...

There is a small wire attached to the starter solenoid, right?

[Casey_SS]

Yes. I didn't touch any of the wiring under the car, just removed and reconnected the interior harness minus the door / cross body section.

[mitchntx]

You have 12V at the starter? How about at the solenoid when the key is turned to start?

Nick is correct ... VATS would prevent it from starting, not engaging the starter.

If the relay is clicking, run a jumper wire from the relay output straight to the starter.

If it engages the starter, it's gotta be in the wiring loom.

[GlennCMC70]

One more thought - back to basics. The only things I changed on the car are as follows:
Battery moved to trunk
2ga wire from + battery to master disconnect
2ga wire from - battery to rear frame rail
2ga wire from disconnect to bulkhead to stock + battery cable going to starter
Stock - battery cable goes to stock ground point near junction box (grounds engine to body)
Alternator & junction box wires originally on stock + battery cable go to bulkhead
16ga wire interrupts + wire on ign. coil via disconnect
Removed door / cross body section of harness
Pulled HVAC, Airbag, wiper/wash, radio accy , courtesy, defog, windows, & radio fuses

That's all that changed from "known good"....anything suspicious here?

BTW - Glenn - there's a relay under the dash with a big purple wire going to it that DOES click when I turn the key to start. Not sure why it's not showing power downstream...no visible problems in the path.

OK, no power downstream (out of the relay). How about power into the relay (upstream)? Not power that makes the relay close, but power that the relay is switching open/closed.