When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
We have a 1970 cutlass 350 that we took out for a drive today. We pull into the parking lot, turn the key, and the thing is still running. Time to go home…
I assume this is something electrical, which isn’t exactly my area of expertise. Does anyone know what might have happened, how to turn the car off, and if the car will be able to turn back on once we get it parked?
Does anyone know what might have happened, how to turn the car off, and if the car will be able to turn back on once we get it parked?
Addressing your 1st question: No. I think that's the reason for the post/thread. Addressing your 2nd question: Disconnecting the negative (-) cable from the battery will turn off the car. Addressing your 3rd question: You most "likely" will able to start the car.
First - turn off the car by disconnecting the negative cable from the battery.
Disconnecting the negative (-) cable from the battery will turn off the car.
Thank you. I was about to get started on this, but my enterprising father instead jammed the key into the ignition position (did not sound great) and then back and it magically turned off.
We were a little worried about the engine getting too hot, and don’t know why this worked out.
The engine can still start, but the first 20 times the starter just clicks when you turn the key. It did this to some extent before, but I think it’s worse now than it used to be.
Thank you. I was about to get started on this, but my enterprising father instead jammed the key into the ignition position (did not sound great) and then back and it magically turned off.
We were a little worried about the engine getting too hot, and don’t know why this worked out.
The engine can still start, but the first 20 times the starter just clicks when you turn the key. It did this to some extent before, but I think it’s worse now than it used to be.
In a panic situation, tough call what someone is going to do in hopes to resolve an issue. Jamming the key into the ignition switch would not be my 1st choice.
In theory (and likely in reality) the engine shouldn't get too hot - it's just sitting there at idle, so this shouldn't be a concern.
You need to investigate what damage was done jamming the IGN key into the IGN SW.
Regarding first 20 times the starter just clicks when you turn the key and did this to some extent previously, it could be the starter solenoid is failing. It might also be the IGN SW itself was failing and may have failed - although you stated you got the engine to start. With that many attempts to try to start the engine, the fact the engine would not shut off leads one to suspect electrical - yes.
First, has any work been done on the car recently? There are many things that will cause this. Alternator, ign switch, starter solenoid, weak battery, dirty/corroded cables, etc..., but few things will cause both preventing the engine to start and turn off. I would suspect the starter solenoid. Next time it won't turn off, leave the key off and put a towel over the carb to force the engine to stall, then check the coil+ terminal for 12v. You may have to separate the wire from the solenoid R terminal from the power feed wire to see which is the culprit.
Seen this many years ago on a '70 Cadillac, quite certain it was a leaking diode in the alternator back feeding to the ignition. Reserving the right to be wrong on this one...been almost fifty years.
Could try unplugging the alternator and turning the key off to see what happens.
First, has any work been done on the car recently? There are many things that will cause this. Alternator, ign switch, starter solenoid, weak battery, dirty/corroded cables, etc..., but few things will cause both preventing the engine to start and turn off. I would suspect the starter solenoid. Next time it won't turn off, leave the key off and put a towel over the carb to force the engine to stall, then check the coil+ terminal for 12v. You may have to separate the wire from the solenoid R terminal from the power feed wire to see which is the culprit.
The battery is definitely on the weak side, but we fully charged it yesterday. The only work I’ve done recently was fixing the automatic choke mechanism.
Seen this many years ago on a '70 Cadillac, quite certain it was a leaking diode in the alternator back feeding to the ignition. Reserving the right to be wrong on this one...been almost fifty years.
Could try unplugging the alternator and turning the key off to see what happens.
I heard someone say that if the alternator is leaking it will be warm to the touch. We always assumed the battery was bad because it always gets hand-me-down battery replacements from the family car, but the alternator may be worth checking out. Thanks
If you have a leaking diode it is very possible the battery is overheating as the ALT struggles to appropriately/adequately recharge the battery during normal operations.
Next time the car doesn't start you might use a rubber mallet to give the starter a couple of good strikes. The starter will sometimes bind and the car will fail to crank if the engine is hot or if the starter is on the way out. If this causes the car to start then you need to investigate either a bad starter, or figure out if your engine is running hot. This happened to Oldsguy; my father, many years ago when I was a baby and he had a 71 Cutlass S.
The battery is definitely on the weak side, but we fully charged it yesterday. The only work I’ve done recently was fixing the automatic choke mechanism.
You said you fully charged the battery. If that is the case, a fully charged battery will read >12.6 VDC. That's a good starting point. To help obtain some pertinent data on your own, I hope you own a digital multi-meter (DMM) or at a minimum a Volt Meter (either digital or analog) capable of reading DC voltage.
See what basic preliminary data you can find from your ALT + BATT charging system:
(1) Turn off all accessories in the car e.g. lights, radio, heater, A/C, etc. - nothing running.
(2) Hookup the meter & measure the DC voltage and write it down.
(3) With the meter hooked up to the battery, start the car.
(4) Measure the voltage of the battery while the car is running. As the engine runs, the ALT continuously feeds current/voltage into the battery to maintain voltage of the battery. A healthy ALT + BATT charging system will demonstrate ~14.3 VDC at the battery w/ the engine running at idle - no accessories operating:
(a) You might get somewhere around 13.8 VDC. It should never fall below 13.8 VDC and it should never go above 15.0 VDC.
(b) Increase the RPM of the engine with the accelerator pedal to say ~2,000 RPM - 3,000 RPM (guess if you don't have a meter). Does the voltage increase on the meter? If so, write down what the voltage is before you increase the RPM and after you increase the RPM.
The steps above will help you to inform yourself and become better acquainted with the basics of your charging system and are good rudimentary starting points to diagnose faulty/aberrant electrical charging issues.
Regarding a possible leaking diode. As mentioned, you can take your car to an automotive parts store, they'll bring out a tester and check your ALT, BATT & Solenoid - for free. This is most likely the easiest for you if you have minimal skills at troubleshooting/diagnosing electrical starting issues. Back to that possible leaking diode. There are at least two or more diodes in the alternator. By itself, an alternator produces AC (Alternating Current) - the type you use in your home when you plug something into the wall receptacle. However, a car uses DC (Direct Current). Since the battery is a DC voltage battery & all accessories operate off of DC voltage, the AC output from a alternator is filtered (changed) to DC current. The diodes trap (filter) alternating current (AC) to provide only direct current (DC). AC runs both ways - back & forth, DC current runs one way. If a diode is leaking, it is possible you're propagating some AC reverse current and not providing a full DC (one-way) current. This can be an issue with maintaining/charging a DC battery since the DC battery wants DC voltage, the voltage regulator operates on DC voltage (not AC), etc. You get the point. This can increase battery heat and reduce battery life to the point of battery failure and premature battery aging.
Jut review what I mentioned above and do some checking on your own to gain some insight. Good Luck.
Last edited by Vintage Chief; March 29th, 2024 at 03:33 PM.
And, just so you know the difference between a fully charged battery and a battery which has lost its charging capacity. It doesn't take much to lose battery cranking amp capabilities. NOTE: 12.6 VDC is fully charged while 12.06 VDC is 50% charged. That's significant.
The steps above will help you to inform yourself and become better acquainted with the basics of your charging system and are good rudimentary starting points to diagnose faulty/aberrant electrical charging issues.
Thank you for the starting point. I took those steps today and the values looked like they were within normal operating range. In the morning, the voltage read 12.89. After I started the car, it read 14.65, rose to 14.78, and fell to 14.48 over the course of ten minutes, with steady voltage on acceleration. Right now I’m looking into testing the ignition switch and starter.
It would be easy to unplug the alternator, start the car and then see if it shuts off. If it does shut off it is a bad diode, if it doesn't it is something else.
It is great that you followed Norm/VC's steps, you learned and now know that the output voltage is ok. The alternator can produce sufficient voltage and at the same time have a bad diode. Diodes have a few failure modes/results.
Thank you for the starting point. I took those steps today and the values looked like they were within normal operating range. In the morning, the voltage read 12.89. After I started the car, it read 14.65, rose to 14.78, and fell to 14.48 over the course of ten minutes, with steady voltage on acceleration. Right now I’m looking into testing the ignition switch and starter.
Great numbers all w/in range.
Originally Posted by Sugar Bear
It would be easy to unplug the alternator, start the car and then see if it shuts off. If it does shut off it is a bad diode, if it doesn't it is something else....you learned and now know that the output voltage is ok. The alternator can produce sufficient voltage and at the same time have a bad diode. Diodes have a few failure modes/results.
I unplugged it, and ran it for a minute. Didn’t have any problems. Next up I might check voltage at the starter. And by the way, I do have a test light or 5 for some reason. Don’t know how we collected so many…
If you plug it back in does the initial problem return?
The inability to turn off seems to be intermittent (my favorite type of electrical problem) whether the alternator is plugged in or not, but the starter clicks happen every startup.
There is a diode setting, but I’m not exactly sure where to put the leads.
I have to look it up each time also. The point though is you want no output to the case from the post. You generally go RED to case then BLACK to post (I think); then, reverse the order (I think). Don't count on my memory. I'll have to look it up, also. Check YourTube or research it. There's a test procedure in my DMM instructions. You might find one in your DMM manual.
Hmm. My experience with starter clicks has been poor connections due to loose battery clamp, corrosion on battery terminals/wires, or th starter solenoid.
I did the test after unhooking the battery, and it gave a reading of 193 in both directions. Doesn’t sound right to me. Could a leak of AC also cause weird noises to come through the stereo? That’s been happening recently and I didn’t give much thought to it.
In regards to starting, we have a starter from a 455. Would it provide any benefit to put that one on, or should I just start with replacing the solenoid? All the battery cables and clamps look good.
I did the test after unhooking the battery, and it gave a reading of 193 in both directions. Doesn’t sound right to me. Could a leak of AC also cause weird noises to come through the stereo? That’s been happening recently and I didn’t give much thought to it.
Yes. An AC leak will cause interference in the radio. You should have DCV in one direction only. If in both directions you have a leaking diode. I'm out of pocket at the moment. Your reading in one direction should be between .400 mV and .800 mV if I'm not mistaken. Plenty of information/videos to test ALT diode(s) out there. Just don't have time at the moment to be more helpful.
If you're still in NJ and need alternator or starter repair, Trenton Starter & Generator on Mulberry Street is very good. They rebuild your part and do it in house.
My 68 did this.
The starter drive gear stop (c-clip) broke which then caused the starter drive to over shoot into the nose. Which kept the drive fork against the contact wheel inside the solenoid.
Basically closing the starting circuit, The solenoids S, R and main battery terminals were held against the contact wheel simulating starting the engine. The starter wouldn't release thus the car stayed running. In my case the starter was spinning with the engine. The nose was cracked too. So in my case it was one and done once I shut it down.
My friends witnessing this whole episode said they've never seen me move as fast as I did from exiting the car to opening the trunk to grabbing a small crescent from the tool box to opening the hood to disconnecting the neg battery lead. They said like 15 seconds.
After installing a new starter I also installed a high quality battery disconnect.
My money is on the starter solenoid or the ignition switch.
MAW replace both main battery cables if they are original or aftermarket junk. Load test the alternator and battery. Rebuild the alt and starter dont replace new junk. Keep the cores.
Last edited by droldsmorland; March 30th, 2024 at 08:52 PM.
I was able to replace the starter today, and found it was covered in muck and had an extremely loose connection. Happy to say there are no more starting issues.
The 455 starter looks like it needs a different bracket, because the support hole doesn’t line up, but I think it will hold for now. The next step seems to be to take the alternator somewhere for a test. To my knowledge, the alternator is original.
March 29th, 2024, 08:50 AM
