Hi all,
Got a 1996 SC300 in overall very good shape and low mileage. It's not being driven much, as it is a "weekend car".
It does not start now on its own but only with a jump. I drove it after a jump, then parked it and it did start on its own after some hours, but longer than that- not.
Checked the battery (only 6 months old) and voltage seems to be fine above 12V. Also checked it after starting and it was above 14V (maybe above 15), so alternator appears to function and charge.

When I try to start now, there are no lights in the dash at all. (Another time, I could hear the tic tic sound of a bad starter. Now, not even that).
*Additional info fyi in case it helps, the following were done 5 months ago: valve cover gasket set, intake manifold gasket set, radiator cap, air filter, spark plugs, plugs wire set, distr. cap & distr. rotor.
Any idea what might go on here?

Many thanks!

 

Hello,

How exactly do you place the Leads when Jumping the car, particularly the Ground Lead?

I've had a similar case a little while back, it turned out that the main Ground Strap that connected the Engine with the Chassis, even though it looked fine on the outside, had rotted completely on the Inside, such that when I attempted to short the Battery with it later on (which, please don't do that if you are not sure if what you are doing), not a single Spark came out. After it would start, the entire car would run on just a few Auxiliary Ground Straps around the engine, which were enough to keep it going, but not nearly enough to stomach the load generated by the Starter.

Testing the Ground is very simple, all you need is to attach one end of your Jumper Leads to the Negative Battery Terminal, and the other to any Solid Metal Spot on the Engine Block, like the Alternator Mount for example, then make sure that the wires are away from anything that's moving and try Starting the Engine, see if anything improves. Make sure to avoid the Intake or Valve Covers for the Ground Points though, while they are technically bolted to the Block, they are attached through Gaskets, which may not provide a solid contact.

Hope this helps and best of luck!

 

Thanks Arsenii. For the ground test, do you mean attaching the black to the negative, the red to a metal part, while the other side of black/red is attached to the other car's battery? (my concern in "playing" with cables is to fry the computer)

 

No, not at all.

The intention is Not to use Jumper Leads for their direct purpose, their task for this test is to serve solely as a Conductor in place of a potentially fried Ground Strap, the task is to use the Jumper Leads to Bypass the factory Ground Strap, if the Starter would Engage afterwards, it would indicate that you need a New Ground Strap.

You only really need just One of Two Leads - connect one end of a Negative Lead to the Negative Battery Terminal, and the other end to just about any Bare Metal Surface on the Engine Block as written earlier, leaving the Positive Lead just dangling freely, not attached to anything, or if you have two Separate Wires (your Jumper Leads are not Fused Together as they often are), you can simply leave one of those leads aside, it is not used at all in this test.

Hope this helps and best of luck!

 

There’s a specific thread about this on the forum you’ll have to search for but it’ll tell you exactly how to fix this issue and what it is. It’s a couple of years old so I don’t remember if it was the security system doing it or not, but the answer to your question is definitely on here. I remember the thread

 

Thank you all.
In the meantime, I checked it at the local O'Reilly auto parts and the reading showed bad diodes in the alternator. This was tricky since one test showed it was OK and then the rest didn't.
It could start once after the battery got some juice but dead the next morning.
I'll look for this thread since it's not fixed yet. If you find it, please lmk. Thanks!

 

Update - resolved for now. The car was at the mechanic's shop for a couple of days, of which they could not find anything wrong with it, including the alternator.
The battery was dead and they charged it. It starts Ok since then.
I was told that if the battery dies completely, a jump and then some driving will not keep it charged. It needed a special charge to get it back to normal, which I didn't know before.
(Reminder - I was with the car at the local O'reilly Auto parts, where they tested the battery (only 5 months old) and the alternator. They got a good charge read for the battery and a good charge but also a "diodes" notification for the alternator.)

If anyone finds the thread mentioned above, I'd still love to read it.

many thanks!

 

How exactly was the test performed? There used to be a time when they would pull it out of the car and put it on an actual, separate Test Stand, was that the procedure performed at the Parts Store, or did they just hook up some tool to the Battery with the Alternator still in the car and called it a day?

I have actually never heard of anything like it before, and that's coming from the guy who will consistently forget about a Dome Light or something else for a whole night at least once every year. I do wonder what is meant by a "Special Charge" in this case, can you get any more details about it..?

There are speculations that Higher Charging Voltage (upwards of 16-17V) can break down the Sulfates that are deposited onto the Plates if the battery sits Discharged for a long period of time or is otherwise completely Unmaintained, but at that point it's pretty much a gamble with a solid chance that you will still need a new Battery anyway, but with an added bonus of a nagging thought that your car may simply refuse to start again when you need it. That's just about the only special procedure that I know about.

That said, as mentioned, all that applies mostly to cases when the Battery was quite neglected for a period of time. If your battery has been sitting discharged for less than a Day (Two at the most, depending on the state of discharge), all you really need is to just start the Engine and drive around for at least 30-40 minutes, that should be sufficient to get the battery back to Full Charge without any negative effects, and unless there are some other issues with either the Car or the Battery, you don't have to do anything more to it.

Again, it depends heavily on what procedures were performed, and how both shops came to the conclusions that they got. To test the Alternator, it's really not enough to just poke the Battery with a Voltmeter and call it a day, especially if my theory about the Damaged Ground Strap is true, which is still an option. Below is a great video that goes into more details on all the procedures that can be performed to test the Alternator, I would strongly suggest to follow all of them and see what results you would come up with.


Hope this helps and best of luck!

 

The test - no pulling of anything, just a hand-held device that reads voltage and could also give some diagnostics.

"special charge" - these are my words, not a quote. I assume that they hooked it to a charging device that they have in the shop. It works so far better than me jumping the car and driving it.
The car was sitting and not driven (and probably with a dead battery) for more that a day. More like weeks. I assume it brought it to a "pretty dead" condition. Not sure about technical specs.
I'm monitoring it to see if this fix sticks. or more will be needed.

​​​​​​​Thanks a lot for sharing this video.

 

Well, that's not a test, tools like that have to do a lot of approximation, as they don't have any physical ways of interacting with the systems, so, just like archeologists, they have to simply make do with what they have available, which can sometimes lead to a lot of rather strange conclusions..

Again, I would suggest to perform the test described in the video linked earlier, there really is nothing complicated about them, but they will give you a much better idea of what's going on than just a simple all-in-one magic box.

Unless they managed to twist the physics into some peculiar knot, your car pretty much is the Charging Device, just not as efficient, seeing that you have to have the Engine Running for, again, at least about 40 minutes.. I was more curious about the specifics of the Device that they are using, whether they are using increased voltage, adjustable ramps, reverse polarity, etc..

At this point then I would strongly suggest to consider getting a new Battery, especially if it's a car that you rely on, or turn Off anywhere but your home or garage. While it could be fine, there is always the chance that a fried battery is the source of the issues you had. If the car sits for prolonged periods of time, either Disconnect the Battery, or, even better, get a Trickle Charger, which would not only maintain the Charge, but it would also do Controlled Discharges, as batteries don't like sitting Fully Charged either.

Hope this helps and best of luck!

 

Thanks for all your recommendations!!!