Loss of voltage kills engine

[bobcatattack]

Hi everyone- I've been a member for about five years but have never posted before. I now have an electrical issue I can't figure out. My wife had my 70 Challenger out last week and called to say it wouldn't start after she had shut it off. Before I could tell her what to check it started. I started it several times after she got home and it seemed fine. I did check to be sure all electrical connections under the hood were tight. All seemed fine, then I went to drive it. It started fine so I pulled out of the drive. As soon as I hit the brakes it died. I put it back in park and had to turn the key several times but it did then start. I have checked the wiring connections under the dash that go to the ignition switch and they are fine. When I was checking them I kept turning the key to see if there was a loose connection. I never found anything. When it does start, it will die if you hit the brakes or just turn on the park lights. I have changed the voltage regulator and still have the same issue. If I wind it up to about 2500 rpm and turn the park lights on it will run but barely. I noticed when I do this the tach needle drops down to 800 even though the engine is still turning 2500. I believe something is dropping the voltage so low to the ignition when any lights are used it causes the car to die. The fact that I need to turn the key multiple times (sometimes) makes me question the ignition switch. Anybody ever had a problem like this?
Thanks in advance for any help. This is a great site with great members!

[ed-pv]

Have you checked the battery voltage and the alternator output?

[Bullitt-]

sounds like a short somewhere,makes me think of what this guy discovered...not the same symptoms but something to think about...
http://www.cuda-challenger.com/cc/index.php?topic=107585.0;topicseen

[Chryco Psycho]

try disconnecting the Tach or maybe it is grounding the coil out through the tach or the  feed wire from the coil

[734406pk]

Hi everyone- I've been a member for about five years but have never posted before. I now have an electrical issue I can't figure out. My wife had my 70 Challenger out last week and called to say it wouldn't start after she had shut it off. Before I could tell her what to check it started. I started it several times after she got home and it seemed fine. I did check to be sure all electrical connections under the hood were tight. All seemed fine, then I went to drive it. It started fine so I pulled out of the drive. As soon as I hit the brakes it died. I put it back in park and had to turn the key several times but it did then start. I have checked the wiring connections under the dash that go to the ignition switch and they are fine. When I was checking them I kept turning the key to see if there was a loose connection. I never found anything. When it does start, it will die if you hit the brakes or just turn on the park lights. I have changed the voltage regulator and still have the same issue. If I wind it up to about 2500 rpm and turn the park lights on it will run but barely. I noticed when I do this the tach needle drops down to 800 even though the engine is still turning 2500. I believe something is dropping the voltage so low to the ignition when any lights are used it causes the car to die. The fact that I need to turn the key multiple times (sometimes) makes me question the ignition switch. Anybody ever had a problem like this?
Thanks in advance for any help. This is a great site with great members!

Your problem sounds like voltage drop due to resistance through the fuse link to ammeter connection. Do you have a wiring diagram for this year vehicle? It will be very helpful. Will you be doing the diagnosis and repair yourself? It isn't difficult to do but requires some basic test equipment and a few tools. The wiring in these cars was marginal when new but now after 40+ years of oxidation etc, things can go wrong, but don't dispare...these issues aren't new and have been repaired before, better than new.

[bobcatattack]

The battery is good and the alt is charging 14 volts. I just loose the voltage to the going to the ignition whenever I use any lights.

Bullitt- That post did give me an idea. I will plug in an extra signal switch just to rule that out. I may need to take the bulkhead connector apart and check everything.

Anybody ever had ignition switch issues? Could it even cause a problem like this? I never see where they are a problem for others.

Chryco- I will try the tach idea. Thanks

I can check the ammeter fuse link. I have a diagram and can dig into it!  Thanks for the reply's!

[734406pk]

Good luck! Post if you need help.

[bobcatattack]

Thanks 6pk, I'll dig into it again tomorrow. The fact that it is intermittent is the hard part. The thing runs perfect till I hit the brakes then I seem to loose the power to the ignition. Sometimes it starts back up with the first turn of the key and other times I may need to turn it ten times! So aggravating!

[734406pk]

Aggravating for sure! Intermittent electrical issues can really be tough to find, but on the plus side, there is only a few areas that can cause this problem.

[JayBee]

Sounds like something to do with the taillight/brake light wiring to me. "Car dies when you put on the brakes or turn on the parking lights". Maybe try pulling out all the rear bulbs and see if the car still dies with brakes or park lights on. If that solves the problem then put them back in one by one until the problem re-appears. Take a good look at the wiring in the trunk too.

[734406pk]

I've got my wiring diagram out. Let me know when you are ready to dig in. I have a ideas so far. A digital volt meter will be helpful if you have one, but a bulb type (not LED) test light will work.

[73440]

I had rolled extra wire behind a battery box on a bike that finally had worn thru and would touch and kill the engine .
Took a bunch of times pushing before found the bare wire.

[dakota]

Back when it was in one piece, my car was having starting issues too.   When I took the main wiring harness apart, the connection for the main power feed was pretty well cooked as you can see in the picture below.   I also found one of the wires (can't remember which one) leading to the starter relay badly corroded right at the crimped connector - it feel off completely when I accidently bumped it with my hand.  I'm not sure if one or both of these issues was the source of the starting problem, but any signs of corrosion or heat damage on the wiring may help you figure out where it's going bad.    Wiring diagrams are a huge help (http://www.cuda-challenger.com/cc/index.php?topic=104759.0) in chasing down these gremlins.   As noted above, these aren't exactly new problems.    Based on finding a number of cracks in the wiring insulation, one burn mark on the firewall from a short, and some sketchy looking "after market" splice connections, I ended up scrapping all of the wiring.   Hope you don't have to go that far.

Good luck!

[734406pk]

Back when it was in one piece, my car was having starting issues too.   When I took the main wiring harness apart, the connection for the main power feed was pretty well cooked as you can see in the picture below.   I also found one of the wires (can't remember which one) leading to the starter relay badly corroded right at the crimped connector - it feel off completely when I accidently bumped it with my hand.  I'm not sure if one or both of these issues was the source of the starting problem, but any signs of corrosion or heat damage on the wiring may help you figure out where it's going bad.    Wiring diagrams are a huge help (http://www.cuda-challenger.com/cc/index.php?topic=104759.0) in chasing down these gremlins.   As noted above, these aren't exactly new problems.    Based on finding a number of cracks in the wiring insulation, one burn mark on the firewall from a short, and some sketchy looking "after market" splice connections, I ended up scrapping all of the wiring.   Hope you don't have to go that far.

Good luck!

  all it takes is one resistive connection in the right place to cause this stalling issue. When the brakes are applied, directionals or maybe headlights turned on etc, the resistance causes the ignition supply voltage to drop so low that the engine stalls. The bulkhead connector pictured is one of the most common causes of electrical issues. They're not waterproof, most are overloaded and 40+ years of oxidation takes its toll. Thankfully there are new harnesses available if needed!

[bobcatattack]

  I believe I have fixed my issue! I had checked and double checked all connections under the hood, at the bulkhead and under the dash. I never found anything that solved my problem. So I decided to do what Chryco has said to do over and over, I put both of the ammeter wires on the same post so the power doesn't go through it. It solved the problem. I can now start the car and turn on the lights, ac, and hit the brakes and the engine stays running! I guess I was lucky it didn't burn anything up. I should have do this years ago anyway based on all of the things I have heard about. I will be installing a volt meter tomorrow. Thanks to all of you for your recommendations to remedy my problem. Thanks 734496pk for being ready with your wiring diagram. Looks like I will make it to the Nationals this weekend!!!