Engine dies shortly after a jump start

My battery has been allowed to discharge and cannot start the car. A jump start gets the engine running immediately, but after a minute or so the engine dies. Can the engine run with a badly discharged battery?

Right now my battery is undergoing a slow charge from my battery charger. Hopefully that will take care of the problem, or my battery may be shot and need replacing.

Anyway, your thoughts about whether or not a car can run (after jump starting) with a discharged battery are most welcome.

Reply to
Papa
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Yes but *only* if your alternator is working property and charging properly. Do you know if your alternator is charging ok?

If not, that could be why the battery discharged (unless you know it was some other cause like leaving your lights on or something)...if the alternator was not charging properly your car then cannibalized the battery instead until it was too low and couldn't support running the ECU, etc.

Reply to
Matt B.

Very good advice.

Reply to
Joseph Meehan

Thanks, Matt.

I had been installing some new headlights, which involved adding relays and a lot of testing (turning on the lights with the engine off ) as I completed each circuit. I don't think I created any shorts. However, doing all of that testing could have completely, or nearly completely, discharged the battery. Anyway, I put the battery on my charger overnight and now it appears to be fully charged again - but I haven't had time to check it out yet.

When I tried to restart the car yesterday right after it died shortly after the jump start, my VDO voltmeter (the one mounted in the car) showed that the needle was pegged all the way to the left. Maybe I did create a dead short somewhere. If so, I have a lot of tracing to do.

Regards.

Reply to
Papa

Follow up:

After recharging my battery on slow charge overnight at the rate of 12 amps, I measured the voltage across the battery posts with nothing connected to the battery. My voltmeter showed about 11.7 volts, which AFAIK is inadequate (should be about 12.6 volts) and may indicate a battery on its last legs.

I then re-connected the battery to the car and was able to start the engine immediately. The VDO voltage gauge read about the same as the no-load 11.7 volts shown by my voltmeter. Revving the engine did not cause the voltage to increase. Turning on one of my lighting circuits caused the VDO voltage gauge to get slightly lower, whether running at high speed down the road, or just idling with the transmission in neutral.

At least now the car will start, will run without stalling, and shows a positive voltage on the VDO voltage gauge rather than pegging to the left like it was doing before charging the battery.

I think I need a new battery. Please let me know what you think. Thanks.

Reply to
Papa

Read DC at the battery with the engine off. Then with the engine on, at about 1500rpm or so, you should get something on the order of 14V+/- at the terminals with a partially discharged battery, dropping back to

13.6V +/- at full battery charge. If you are seeing anything less than this, either your voltage regulator or your alternator is suspect.

If you have 12.6V steady-state with the car off, that is the correct standing voltage for the battery. Less, the battery is suspect. On occasion, a regulator will fail and in the process boil out a cell in the battery, leading to the next question:

Have you checked the water in the battery? Even so-called 'maintenance free' batterys can be checked.

Peter Wieck Wyncote, PA

Reply to
pfjw

Hi Peter. Thanks for responding.

Yes, I checked the water before charging the battery. It was low in all cells (just about level with the plates, or slightly lower), so I had to add distilled water before recharging. During the recharge no signs of heat or fumes appeared.

I just checked my voltmeter readouts again, with the battery connected to the car. With the engine off and nothing turned on my voltmeter read about

11.5 volts. With the engine running at 1500 RPM and nothing turned on my voltmeter read about 11.0 volts. Turning on an item such as the parking lights caused a slight lowering of the voltage, regardless of the RPM.

Regards.

Reply to
Papa

Mpffff.... It really sounds like either your voltage regulator or alternator has crapped out. That was my immediate thought based on your statement that it would not run _at all_ unless it was still jumped or the battery was recharged. In any case, the cure is the same... new/rebuilt alternator with new regulator. And if the existing battery is 'older', a couple of deep discharges will pretty much kill it as well, so you may be in need of a complete transplant, battery & alternator.

Good luck with it.

Peter Wieck Wyncote, PA

Reply to
pfjw

Sometimes it won't, and sometimes a battery is just plain shot and must be replaced. I've had the same situation several times -- it'll jump-start, and then die. The battery just won't take a charge anymore.

Used to be that a battery died gradually, you'd hear the engine crank slower and slower, the lights got dimmer and dimmer, and you knew well in advance that it was going. Nowadays, it's just and they're dead. I suspect it's because all of the digital circuitry in modern cars has a threshold voltage below which it won't operate, whereas in the old days the lights just got dimmer and dimmer until the voltage went to zero. Five or six years is about all you can hope for from a battery.

Reply to
Brian Running

Reply to
none2u

You're probably correct, but one more question before I start buying parts - could a dead short cause the same symptoms? Thanks.

Reply to
Papa

On the alternator, the brush/voltage regulator are usually one assembly and are usually replaceable separate from the alternator (and are cheaper...about $40 or less for the brush/regulator). Before you buy an alternator, pull the brush/regulator out and check the length of the brushes against the specs in the bentley. if they're below minimum spec, just replace the brush/voltage regulator only. Also, they are spring-loaded (as they wear, a spring pushes them out) and make sure they are not just gummed up and "stuck". That can happen...a diesel Eurovan driver on another list had that problem recently. The brush/regulator usually just unbolts from the back of the alternator via a couple of screws. It's a 5-minute thing to check/change it.

Reply to
Matt B.

Excellent suggestion, Matt. I found several in the $20 to $45 range on the internet.

As it turned out, the fault was due to the voltage regulator. A couple of small 18 gage wires were pulled loose (probably because of my big hands while I was installing new headlight wiring in tight spaces). These 2 wires (one was brown so it must be a ground) are located at the end of the alternator opposite the pulley. Not sure what they are for, but I assume they are part of the regulator circuitry.

After reconnecting these 2 wires, the VDO voltage gage started showing voltage levels above 12 volts with the engine running and all lights on. Before reattaching these wires the best I could get was 11 volts with the engine running and just one set of lights on. I'll do a more precise measurement tomorrow.

I think I'll get a new voltage regulator anyway, since the cost is low and my existing one is very old and probably has nearly worn out brushes.

Thanks to both of you, Matt and Peter. Very much appreciated.

Reply to
Papa

If your meter reading of 11.7 is correct - after an all night charge of the battery - it's on it's last leg and will fail soon. The replacement of the brushes is simple and ususally can be done without removing the alt. from it's mounts.

Reply to
samstone

Final tests after Voltage Regulator wiring repair:

Ignition key off current drain test --- less than 0.1 amp (actually less than that) Negative battery terminal disconnected from ground cables, one multimeter lead connected to negative battery post, other multimeter lead connected to ground cables.

Engine off, ignition key off, battery voltage test --- 12.38 volts Battery fully connected to car's system, multimeter leads connected across battery posts.

Engine on, 1500 RPM, voltage test --- 13.8 volts Battery fully connected to car's system, multimeter leads connected across battery posts.

Reply to
Papa

Fixed then!

Congrats!

Peter Wieck Wyncote, PA

Reply to
pfjw

Thanks. All of you helped me resolve it quickly. This is a great forum!!

Reply to
Papa

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