After Boost Jeep Stalls

[TurtleJack]

I have a Jeep Cherokee. 1992. My battery died two days ago and I got a boost but it stalled immediately after taking my foot off the gas. I then started it again and revved it for awhile but as soon as I took my foot off the gas it stopped. Without having the cables hooked up it doesn't start at all. Seems something is going on with the gas flow. I've been boosted at least 3 times in the past two months because my battery dies and I'm an idiot who leaves the radio going for about ten minutes. My gauge doesn't seem to indicate my battery is low but aside from this I've been boosted successfully until now. I'll take it in but I don't want to have them logging in hours trying to figure out the issue either. But I hope with some answers it narrows it down for us.

 

[Zenmervolt]

Battery is so dead/damaged that it cannot supply enough current and you're running entirely off of your alternator, which is trying to sink so much current into the battery that it cannot keep up at idle, causing the engine to stall.

Leaving the radio on for 10 minutes, unless it's a ridiculously over-powered aftermarket system, isn't even remotely close to enough drain to kill a good battery.

My guess here is that you have a bad battery and a weak alternator/voltage regulator.

Regardless, the issue is unlikely to be fuel flow; fuel flow problems generally mean that the engine runs fine at idle but stumbles when you give it more throttle.

ZV

 

[LTC8K6]

Yes, this is most likely a battery / charging system problem.

 

[TurtleJack]

Battery is so dead/damaged that it cannot supply enough current and you're running entirely off of your alternator, which is trying to sink so much current into the battery that it cannot keep up at idle, causing the engine to stall.

Leaving the radio on for 10 minutes, unless it's a ridiculously over-powered aftermarket system, isn't even remotely close to enough drain to kill a good battery.

My guess here is that you have a bad battery and a weak alternator/voltage regulator.

Regardless, the issue is unlikely to be fuel flow; fuel flow problems generally mean that the engine runs fine at idle but stumbles when you give it more throttle.

ZV

Fantastic, thank you for your time and knowledge. Much appreciated!

 

[TurtleJack]

Yes, this is most likely a battery / charging system problem.

And thank you. The confirmation is reassuring.

 

[LTC8K6]

A similar thing happened to me on vacation. The battery in my 2008 Jeep GC with the Hemi just gave up one morning.

I got nothing when I turned the key. One cell was completely gone and the voltage was right at 10V, meaning the other cells were weak, too.

Tried to jump start it. It cranked over great while hooked up to the other vehicle. But it would not actually start.

My battery was so bad, that it was dragging the voltage too low for the engine computer to be happy. There is such a high electrical load on modern vehicles. If the computer doesn't see good voltage, and good signals from the sensors, the engine just won't fire up.

We had to wait about 15 minutes for my battery to recover just enough to get the system voltage high enough. Then it finally fired up.

Old vehicles don't have these problems. There is no engine computer looking for proper voltages and proper signals from sensors.

 

[TurtleJack]

Okay, so the update is I went and got a new battery, put it in and it started! I thought that was that... However, I went to start it today and dead. It's not clicking so it sounds better than the last one but seems something is draining it. ?! Do all signs point to alternator or am I showing my mechanical ignorance?

 

[TurtleJack]

A similar thing happened to me on vacation. The battery in my 2008 Jeep GC with the Hemi just gave up one morning.

I got nothing when I turned the key. One cell was completely gone and the voltage was right at 10V, meaning the other cells were weak, too.

Tried to jump start it. It cranked over great while hooked up to the other vehicle. But it would not actually start.

My battery was so bad, that it was dragging the voltage too low for the engine computer to be happy. There is such a high electrical load on modern vehicles. If the computer doesn't see good voltage, and good signals from the sensors, the engine just won't fire up.

We had to wait about 15 minutes for my battery to recover just enough to get the system voltage high enough. Then it finally fired up.

Old vehicles don't have these problems. There is no engine computer looking for proper voltages and proper signals from sensors.

Older, as in a 92?

I appreciate your story and input. The new battery didn't take either... :/

 

[LTC8K6]

If you can use a multimeter, measure the DC voltage at the battery terminals with the engine running. Or if there is a voltmeter on your dashboard, you can just look at that if it works.

That's a basic test to tell you if you have a working alternator.

You want to see about 14.5 volts or so with the engine running.

With the engine off, you want to see about 12.5 volts or so.

 

[Zenmervolt]

Starting to sound as though there's a short somewhere that is causing a drain with the engine off or the alternator is not supplying enough current to charge the battery once the engine is running.

Testing voltages will tell you whether the alternator is working and will give you insight into what the battery's state of charge is, but likely won't show you parasitic loads while the engine is off. To do that you'd need to measure current draw, which I generally don't recommend to a novice in cases like this since, depending on the amount of current draw, it may be too much for a cheap multi-meter to handle.

ZV

 

[tortillasoup]

Starting to sound as though there's a short somewhere that is causing a drain with the engine off or the alternator is not supplying enough current to charge the battery once the engine is running.

Testing voltages will tell you whether the alternator is working and will give you insight into what the battery's state of charge is, but likely won't show you parasitic loads while the engine is off. To do that you'd need to measure current draw, which I generally don't recommend to a novice in cases like this since, depending on the amount of current draw, it may be too much for a cheap multi-meter to handle.

ZV

to further this point, a bad diode in alternator, bad ignition switch, radio or some other stuff can cause such a drain....


I would also clean up your electrical grounds sufficiently shiny as that can affect charging rate though that wouldn't necessarily explain a dead battery overnight.

 

[Sabrewings]

I suspect a parasitic loss as well. That's the only reason a new battery should have died like that.

How I would proceed:

1.) Throw the battery on a stand alone charger. If you don't have one, I suggest getting one. They're very useful. I have a Schumacher. Otherwise, connect a donor car for a while before starting (30 minutes), then disconnect.
2.) Start the car.
3.) Check voltage with the car on. Is it around 14V or higher? If so, congratulations. Your alternator seems to be in good shape. You could even wait for the car to warm and drop to a normal idle and verify voltage at the alternator's slowest speed.
4.) Stop engine. Turn on headlights for 30 seconds, then turn them off. Now check battery voltage. 11.8 or higher? Battery seems ok.
5.) Remove the negative battery terminal and connect a multimeter inline in ammeter mode. You should see very little current being drawn on such an old vehicle. Under a tenth of an amp. If you see more, start pulling fuses until it drops to acceptable levels. Whatever you pulled to get it to drop has your drain. Troubleshoot from there.