ewskater92

I have a 1986 IROC-Z28 camaro with an GM Goodwrench 5.7L engine and a carb setup. Every time I press the brakes after the car heats up the engine just dies. Its instantaneous which leads me to believe that ignition is losing power. I'm not sure why. I've checked the ground wire behind the block both on the head of the block and on the firewall. There's another ground wire next to the battery that goes to the chassis. Those are all fine. The car has no problems until it heats up.

Any ideas what may be wrong? Any help would be very much appreciated because I'm pretty pissed at my car right now. Trying to get her ready to take back up to school with me and she doesn't want to leave the garage...

ewskater92

Any ideas?

Berlinetta00

If you have a ruptured brake booster diaphram, you could be causing a massive vacuum leak every time you press the brake pedal. When the problem occurs, remove the vacuum line to the booster and plug the engine side, then attempt to start the engine again; if you can now run the engine and not have it die when you step on the brakes, the booster is shot. It may work with the engine cold because the fuel ratio is richer, allowing for the engine to still run with the excess air coming in.

ewskater92

Its definitely not the brakes. I can have the car moving down the road and hit the turn signal and then the engine dies. I've even had it die just out of nowhere. This is a problem with the car losing power to the ignition and I'm not really sure where to go now that I know this.

Any ideas?

Berlinetta00

You can try a few other things, like sequential fuse removal to isolate the fault. When it dies, does it start right back up? Have you ensured that your battery connections are tight, system voltage is correct, wiring is properly routed?

ewskater92

The sequential fuse removal sounds like that could help. I've never done that before. Could you explain the process?

And when it dies it does not start right back up. I usually just turn the ignition all the way off, put it in park, and then turn the ignition back on and it just magically works... Battery connections are tight. I'm checking wiring on the starter because we just recently put a new starter on the car and all the wiring on the starter was tight. The system voltage is reading a little over 12V. There's no problem starting the car or running the car. It just sporadically loses power to the ignition and turns off. So I'm looking over all the ignition wiring to see if there's any obvious shorts or wires coming disconnected.

ewskater92

Is there a wiring diagram somewhere that would include all the wiring for the starter? I've been looking and found a wiring diagram on Autozone's website but it doesn't have the starter on there. Right now My wiring is just for a starter, battery, alternator, and fan because the TPI is out of the car along with all the wiring and the computer so idk if there's a wiring diagram that would cover what I have left?

Berlinetta00

Alright, I'll take a page right out of my handy textbook here for the wiring, it kind of sounds like some mods have taken place in the harness over time. So, this is going to be rather long winded, but it should give you the foundation in the schematic and testing to determine where the short is or what exactly is happening.



In the diagram above, you can see the main power going straight from the battery to the starter, with a junction that goes to the alternator. From the starter on the main positive terminal, another junction goes up to the ignition switch. Both of these junction wires have fuseable links, these are easily checked with a multimeter for resistance across the fuseable link section (or voltage drop for one that has 0 ohms of reisistance but exhibits wear). These are essential for proper charging and starting operation. From the starter to the ignition switch, there are no further breaks or junctions, and if this fuseable link goes out no accessories will recieve power at all. The ignition run wire goes from the switch through the PCM then to the distributor, and is entirely independant of the lighting system, aside from the ignition run portion of the wiring, which is where I suspect the fault lies. This indicates that one or more of your accessories is drawing a substantial amount of current and not allowing the current to travel through to the PCM or distributor.

This indicates that you need to first check system voltage and then perform "ground fault isolation" which is fancy for saying isolate the current draw and remove it from the system to determine which system requires repairs.

System voltage should be 13V to 14 V measured at the battery while at factory idle speed (700 rpm ish for autos). If you are recieving less than 12.5v at idle, try the reading at 1500 rpm. If you are still below 13v, there is a charging system problem and will require further investigation.

Isolating the fault can be done a few ways. Sequential fuse removal involves removing a fuse for a specific system, like your brake light fuse, and seeing if the problem continues. If it does not, then you have isolated the fault to one system. This is a rather impercise method and ground fault isolation is generally preferred.

You can isolate faults to ground by checking continuity from different points on the positive side of the circut to ground, meausred with the vehicle off, switch in the off position. The positive terminal, measued to the negative, should give you an "OL" or no continuity. The same should be true for just about every fuse in the fuse block, and the positive wire going to the distributor. If you test the postitve side to any circut and recieve a 0 ohms reading, that system is shorted to ground. For a cross system fault, you can check your reading at the ignition switch on the "run" terminal, then apply the brake pedal and see if your resistance changes, same process for the turn signals and any other accessory. If your resistance does not change with any of the other accessories on, you have eliminated a ground fault to the ignition switch through the other accessories.

What is the system voltage currently at idle measured at the battery and alternator? What is the system voltage measured at the same place with the headlamps on and the AC (if equipped) on?

W.E.G.

The fact that the ignition circuit fails when you jostle the turn signal is a pretty good sign that the problem is the wiring somewhere in the steering column. Probably somebody messed with the ignition wiring in the steering column (likely somebody's incompetent attempt at alarm installation) and didn't get it back right.

Is today a full moon for visitations from the ghosts of haphazard alarm-system installers?

W.E.G.

The wiring diagram is cool stuff, and may be very helpful.

I still think the first thing you are looking for is electrical tape and/or butt-connectors in places the factory never would have put any.

mwarner44

If it happens only when you use the turn signal or brake it could be faulty wiring to the rear stop light. I would start there. Maybe pull the stop light fuse and see if it still does it.

ewskater92

Thanks a lot Berlinetta00! I'm going to test some stuff out. I think I'm going to try pulling some fuses first since that seems easiest. And then after that if I haven't found a problem I'll try the ground fault isolation. Sounds like a little more work but definitely doable.

And to W.E.G. they put an aftermarket security system in the car. It's a Rattler 300. It has been nothing but trouble really because the clicker for it doesn't really work well. So I pulled all that out from under the dash.

loco823

I too am having the same problem with my 91 Camaro and I was just curious if you remember what caused your car to die when hiring the brakes? I noticed that the post is over a year ago but I'm starting to go crazy with this.