I have an 87 IROC-Z with a built LT1 (carbureted) swap that I'm having issues with. After the build I had zero issues for quite a while. About a month ago, I went to shut the ignition off, after a particularly heavy footed drive, and the key didn't kill power to the engine. It turned off the instrument panel lights but the engine kept running. I have separate switches for the fuel and coil power so I was able to get the car to shut off by turning those off. I am able to start the car without issue at this point however the key still does not turn off the car.

Additionally, when this started happening, I noticed my battery voltage is slowly dropping while the car is running. At first I thought it was an alternator issue however even a new alternator did not fix the problem so I am assuming the two issues are connected. I do not want to do damage to my alternator since something is clearly drawing the battery down. I have not been able to find any shorts to ground in the engine bay and I've gone as far as disconnecting different electrical components to see if the issue stops.

Is it possible for the ignition switch (typically mounted above the steering column...not the key switch) could be damaged? Or maybe the ignition lock itself is faulty?

Anyone have any ideas on what to check out? The ignition switch and ignition lock are both cheap and readily available but I'm not sure I want to dig into swapping those if it doesn't make sense.

 

Given your description of the problem I'm left to wonder if the wiring isn't quite right with the swap , and maybe your drawing too much power from that particular set of switched contacts in the ignition switch , which may have now "welded" themselves closed and are not allowing the rest of the switch to operate properly ? A look at the factory wiring diagram will show that the current for things like the fuel pump and the electric radiator cooling fan are not sent through the ignition switch , but are instead switched from relays fed from fusible links , do you have such high current items being fed from your ignition switch ?

 

I currently have my radiator cooling fan, fuel pump, and ignition coil all wired to switches completely separate from the ignition coil. I can't think of anything that would draw major amps off the top of my head other than the starter/solenoid that would be going directly through the ignition switch. I have a pretty high powered stereo system in the car that draws a lot of amps. Since it is carbureted there aren't nearly as many things that could "go wrong" from a wiring stand point compared to fuel injected IMO. I think I'll go ahead and drop the steering column and at least inspect the ignition switch for major electronic failure damage and go from there. I work in electronics and, correct me if I'm wrong, but the ignition switch should just function like a large relay correct? It was just odd to me that the car has been running great after the swap for probably close to a year and a half without issue then all of a sudden this occurred.

 

Yes , the ignition switch could be compared to a relay in that it's got several sets of switched contacts all operated from a common mechanical action (a coil moving an armature for the relay , and the pushrod from the lock cylinder for the ignition switch) .

 

That's was my initial thought as I read your post. Keeping Power on the PINK wire rather than killing it. The heavy gauge PINK wire feeds the Coil, Distributor, GAUGES fuse, & other "engine control" / ECM stuff.

That box is where I'd start looking too, but I'd be prepared not to see anything and would just probe the wiring first. Probably a good idea to get a replacement in advance of unscrewing anything under there.

 

I already picked one up just in case. I found a couple of other threads where guys had replaced that to resolve some similar issues with the ignition not getting voltage. I'll poke around with my meter before I pull everything out.

 

If you wired the power source for fuel & spark to a switch panel then the engine will run indefinitely until you cut one or the other. All the key switch does at that point is operate the starter motor. In other words, you may have done this to yourself.

If the alternator is a type that needs field excitation to operate, then I'd check to make sure that's wired up properly. That could explain why the alternator works on test bench, but doesn't in your car.

 

For whatever reason, the alternator's field winding is still being excited after you turn the key off.
Therefore, the alternator is what is keeping your engine running.
A diode probably needs to be added into that circuit to prevent this.

EDIT: this can happen when an aftermarket ignition box is installed.

 

No no no, the alternator has nothing to do with shutting down an engine. You shut down an engine by cutting fuel or spark.

He's either wired around the key switch so that the key switch is not the master electrical switch anymore, or he's got an undersized relay feeding that power panel that has welded the contacts because of too much switching current.

Even if my guess is wrong this problem is seriously easy to diagnose. Should be able to track it down in 5 minutes using a voltmeter.I mean, you even know which circuit to check!

 

The ignition switch ended up being in really good shape. I did some checking around with my meter and ended up finding a faulty relay that was completely fused together internally causing the primary issue. Additionally, I found that the wire that feeds the alternator field source was covered in corrosion and with a slight pull actually broke. I re-ran the wire and fired everything up last night. Everything is working like a charm now.

 

Of I only had a nickle for every time that's happened !!

Good to hear that you got found that relay,.... Keep a close eye on it's replacement if nothing else was changed; either the relay was bad/defective,... or something else caused it to melt.