Hello,

Sometimes, not all the time, all my '77 will do when I turn the key forward to turn it over is let out a "chunk" sound. Then, there is no power. Car is completely dead. I come back a couple of hours later and the power is back but the starter "chunks" again and the car is dead.

Sometimes there is no power after a couple of hours and other times the car will actually turn over.

I have replaced the starter, the negative battery cable and the fusible links. Battery and alternator check out fine.

I get 12.6 volts at the starter but I get far less at the alternator. Should I be getting 12.6 volts at the alternator when the ignition is in "run"?

Also, one time after the starter went "chunk", I noticed that there was no power at the starter. ?? I disconnected the starter and checked the battery cable at the starter and it had 12.6 volts. Hooked it back up and the car went "chunk". Another time I did the same thing and the car turned over.

When there is power in the car, the headlights work. However, one time this past weekend I put the car in run (did not attempt to turn it over) and put the head lights on and it killed the power in the car.

I'm thinking the ignition switch might be bad. Thoughts?

I appreciate your insight.

 

It sound like your battery is about as dead as it can be. Be sure to replace the engine block-to-frame 2 gauge aluminum ground cable with a 4 gauge copper cable because those OEM aluminum cables get internal corrosion over time and quit carrying current.

 

It sounds to me like the main battery cable (+V) to the starter is bad. The car went "clunk," then you had no voltage at the starter. Wiggling the cable a little during removal probably caused it to conduct again (temporarily).

 

I second 454luvr's post. another possibility is the threads in your battery are shot. for most side posts they have aluminum inserts so its harder to strip them out. but if they are the aluminum can simulate good threads when they are not and then loosen out over time. I had that discrepancy recently with mine.

 

Now this makes sense. Bad positive cable. I don't think it's the side posts - they're very clean and the connection I know is excellent but much like the negative cable, which also looked great inside the car, once it goes out of the car it got ugly.

I understand replacing that cable is challenging but it can't be as challenging as trying to actually diagnose what the problem is.

Also, and this goes towards the idea the positive cable is bad, after the starter goes chunk and there's no power, there's no power at the starter. However, when I checked the cable after I removed it there WAS power. So that would mean that my jiggling the cable got it to work, right?

If the positive cable was good, there should always be power to it. That chunk sound would come from a bad starter which I know is not the case.

Thanks for your insight. This has helped me greatly already!

 

Well, turns out it's not a bad battery cable. I bought a cable from Advanced Auto and the car continues to have no power. Here's what's really odd - when the positive cable is attached to the starter, there's no power at the starter. When I remove the positive cable and test it there is power. ?? So, obviousl the problem lies somewhere else.


I also tested the resistance on the positive cable in the car and it's ok. Fusible links are fine, negative battery cable is new, ground to the block from the starter is solid.

Here's what really odd - when the positive cable is on the starter, there's no power in the cable at the starter. When I remove the cable from the starter there is power. ??

This tells me there's a short somewhere.

I'm thinking ignition switch. Thoughts?

Also, is the neutral safety switch part of the ignition switch that's at the end of the steering column?

 

Just to be sure we're on the same page regarding terminology...

When the starter goes "clunk," how are you measuring power at the starter? I assume you're using a high-impedance voltmeter of some sort. Describe the exact points where you're touching the positive and negative leads of the meter.

 

I put the positive lead of the meter on the part of the positive end of the battery cable that attaches to the starter - that large bolt. Then I touch the negative lead of the meter to the frame of the car. When the positive battery cable is attached to the starter, and there's no power in the car, I don't get 12 volts at the starter. When I then remove the positive cable and test it off the starter I do get 12.


This not the way I should test this?


Thanks in advance for your insight!

 

Sounds like a dead cell in the battery or a bad ground . That main power cable to the starter is always powered up so if it shows power then does not show power its the battery .

 

You're doing the right thing, you just didn't go far enough. Next time it goes clunk, test the voltage at the starter again. If there's no power, don't touch anything, but test directly at the two battery terminals. If you have power there, test at the starter one more time. You're either losing it inside the battery, or a clamp or cable is bad. This should tell you if the battery is doing this.

 

Nothing is making sense. I've tested all the cables - they're fine - and tried new a positive battery cable and even tried a different battery. The car still has no power.


When there is no power at the starter there IS power at the battery when I test the battery cables inside the car AT the battery.


Why would there be no power on the positive battery cable when it's connected to the started but when I disconnect it there IS power?

 

Where does the negative battery cable connect to the frame in your year? Is it possible the lug isn't making good contact, that corrosion on the frame might be insulating the connection?

 

It's on the frame just outside the "bucket" where the battery goes. I replaced the old one with an Autozone cable. I'll check that again.

Is it not unusual to not have 12 volts at the starter and to have 12 volts on the positive battery cable when it's off the car? That's what's really throwing me.

 

There are a couple issues here having to do with how the measurement is made. I assume that when you unbolt the cable at the starter, you're still using the same ground reference for the negative probe of the voltmeter. Using a different point on the frame or block might change the results. Second, the positive current path doesn't simply end where the positive battery cable connects at the starter. The starter terminal is the junction for much of the positive voltage going out into the rest of the vehicle. If your negative cable isn't making a good contact to the frame, even a small current draw into the rest of the vehicle might be enough to drop all the voltage across that connection and cause zero volts when you measure between the frame and positive cable (after the "clunk"). When you disconnect the positive cable for the starter, that draw into the vehicle disappears. Your meter draws almost nothing, microamps, and that allows you to measure a positive voltage even though there's still a high-resistance connection in the path. I don't know for sure that the culprit is the negative cable at the frame, but it's a good possibility considering everything you've changed out. I hope what I'm trying to convey is clear about voltage and current. I'm at work right now, but I could post a sketch when I get home that might help to explain it better.

 

And you don't think it could be a bad ignition switch or faulty neutral safety switch?

I'll take the ground off again and try them again. I bolted the new negative battery cable to an exhaust bracket that bolts to a cross member just in front of the differential. Perhaps I should bolt it back where it came from. I'll be darned if that's the culprit but hey, y'never know. I appreciate your insight!

That diagram would help me out too.

 

Have I misunderstood the symptom? I thought you meant that there's no voltage when you measure from the large red battery cable at the starter to ground. That cable doesn't go through the ign or neutral switches.

 

If you're talking about the cross member I think your talking about I don't think it would make a good ground.

 

Correct. There is no power at the red battery cable when it's attached to the starter. However, there is power at the red cable when it's off the starter.

Perhaps it's as "simple" as a grounding issue?

 

Try connecting a jumper cable to the negative side of the battery and the other end to a good ground on the engine.

 

That's a great idea, BlackC3vette. Of course, I tried the positive side of the battery to the starter an of course, nothing.

Also going to try putting the new negative cable back on the frame where it was originally. Right now it's on cross member in front of the differential. 454Luvr says that might not be the best place for a ground.

Wish me luck! :-)