I tried posting this in the general maintenance section, but haven't gotten any responses in two days, so I thought I would come right to the LT1 source...

About two years ago I took the interior/HVAC out of my '93 Z28 (planned on making it a budget race car). After I got done, it wouldn't start. The starter was slow before all the work (but it always started and ran fine), so I just figured it went bad. Replaced the starter, still nothing.

Two years later I finally have time to mess with it again. Symptoms are: No crank, no click, nothing. Everything else in the electrical system works fine, just nothing when I turn the key to start it. The only thing that happens, at all, is the red "BRAKE" light comes on as I'm turning it, and then the yellow "ABS INOP" light comes on for a few seconds.

I've worked all day narrowing things down, but now I'm very confused as to what it could be, and here is why:

1. I found and tested the starter relay. Works fine. 0V before the key turn, 12V out as it's turned. So everything must be working up to the Starter Relay, right (maybe this isn't true?)?

2. The only thing I'm aware of between the Starter Relay and the starter solenoid itself is the Neutral Safety Switch. I tried testing it, but it was cheap to replace, so I just got a new one and replaced it. Still nothing on the key turn.

3. I took 12V from the battery directly to the "S" terminal on the starter solenoid (where the purple wire is attached), and immediately the engine started turning over perfectly.

With those three things I am stumped... any ideas?

 

If you don't get 12v on the purple wire at the starter when they key is turned to start and the starter enable relay is sending 12v out then you need to chase in between the two things to find out where you are losing your 12v. See if you are getting 12v out of the transmission position switch toward the starter.

 

I just bought a new one and replaced it, so I assume it's ok, but I'll check that to make sure.

Edit: Also btw, I tried jumping the green wire to the purple with the neutral safety switch unplugged (with a paper clip), but that didn't do anything. I also got 0V between the paper clip and ground at that point too... so I'm not sure what that means really. haha

 

Alright, so with the assistance of my sister to turn the key for me, which I didn't have earlier today, I have found some new things... It explains something suspicious I noticed earlier today too.

There are three wires I measured: Yellow (key to starter relay), Green (starter relay to neutral safety switch), and Purple (neutral safety switch to starter solenoid). What I found was this:

Yellow - 0V until key turn, and then 12V, good.

Green - 0V always, if plugged into the neutral safety switch. Or, 12V always if key on and unplugged from neutral safety switch.

Purple - always 0V (could only get voltage from Green, which is 0V if plugged in...).

So, I was confused how the green wire could be 12V if it was disconnected from the neutral safety switch and getting nothing from the starter relay. Then I remembered there was something else connected in the middle of the green wire in my Haynes manual diagram, and that the Brake Transmission Shift Interrupt Solenoid was getting really hot earlier today (couldn't touch for more than a second). So I tested that. When plugged in to it, the green wire was at 12V, but when unplugged it was at 0V, like it should be (I believe). The other wire coming into it was 12V always. So it appears this may be just closing the loop between the green and the other wire.

I do remember when the car was working fine before that sometimes the brake wasn't necessary to shift into gear, and that is what happens if you unplug the solenoid, which leads me to believe it had been going bad. And the "BRAKE" light comes on on the dash when attempting to start it now, if that means anything.

How does this Brake Transmission Shift Interrupt Solenoid operate normally (electrically), and could it be causing the problem?

Thanks for your help!

Edit: Looks like the Brake Transmission Shift Interrupt Solenoid I saw on a diagram is also being called the "Brake Transmission Shift Interlock"

 

Is the sequrity light flashing? Have u tested the key? The Resistor i mean. This sounds like a sequrity issue. When mine started flashing i had nothing after that.

 

Nope, no security light.

 

Try unplugging the BTSI and see what happens.

 

Alright, after a busy week I can work on it again...

So, if I unplug the BTSI should it be able to start normally? (as in the problem is something else?)

 

I had something exactly like this happen to me when I removed all my dash and HVAC stuff. Come to find out I removed the Theft deterent relay or what ever the hell its called. It is a silver box thats about 4"x4"x1", There was also a little black box that was about the same size. Sure enough plugged them back in and started right up. Sorry I cant think of the names of the actual parts but I know it has something to do with the VATS, security related. Hopefully this helps, good luck!