Jump-start chaos - I have a strong suspicion!

Hi,

I have a question about a problem a friend of mine is experiencing.

Here's the translation:

"The vehicle is a JEEP Cherokee, manufactured in 2002. When the lights were turned on, the battery was completely drained. Afterwards, a jump start was attempted using another vehicle. During the jump start, both cables (positive and negative) came into contact with the Jeep, and there was a significant spark." The whole thing was immediately discovered. That's how it was explained to me.

After that, the vehicle was restarted, but it would stall while idling. You have to press the accelerator to keep it running. The fuses and other components were checked, but the defect persists.


To me, it sounds like the engine control unit (ECU) might be damaged. At the very least, something related to the idle speed control has failed. What do you think? I've suggested that he start by reading the error codes.

I would instinctively suspect that the Plus cable might be shorted to ground somewhere. Depending on where it happened, a large electrical cable could have been burned through, or something could have been welded onto it (an extreme example: jump start cables falling onto a fuel injection line...).

Regards,
Guste.

For your information:

The vehicle is a gasoline-powered car. Today, it will be checked for error codes at the , and then we will receive the results. I will report here if there is any new information.

"To me, it sounds like:"
Battery completely dead, and possibly the alternator is damaged.

Because a gasoline engine needs a lot of electricity to run, and if the battery doesn't provide it and the alternator isn't supplying it, nothing will work.

m;

Hi,

There's some new information.
The vehicle sustained no damage. In the morning, after driving a few kilometers, the scooter stopped accelerating but didn't turn off. (The battery was probably being recharged by the ride).

Despite this, he drove the Jeep to the diagnostic tool to read the error codes, but the vehicle then stopped working again. The friendly person then told him that everything was okay, but he would need to drive the car for a while so that the system could recalibrate itself. (Perhaps it's related to the throttle body?)

As promised, done.

The vehicle is running again, no problem.

"Question: Are engine control units (ECUs) somehow protected? Or do they have built-in safety mechanisms to prevent such events?" Best regards.

luiggi wrote:

Question: Are engine control units (ECUs) somehow protected? Or do they have internal safeguards to prevent such events? Sincerely

Most of the time, they are protected, but not against 200A. If you overdo it, you get everything briefly.

In the event of a short circuit, very little can happen because the control units only receive an undervoltage. I once experienced the same problem with the engine stalling in the LL (low load) on an Escort (2.0) that had a faulty battery (a cell was defective).

Really?

I always thought that a short circuit involved high voltage surges. Or am I wrong now? Best regards.

At the moment of the short circuit, the voltage drops (=undervoltage). Very high currents can flow, which can damage the battery and also cause cable or circuit board connections to burn out (similar high currents to those found in a welding machine).

At the moment the short circuit is cleared, however, one or more very short (but high) voltage spikes often occur.

Due to the inductance of the wiring, it acts like a coil that wants to maintain the flow of current, and therefore causes a significant increase in voltage when the short circuit is cleared.

You are both right .

PS: Only the (harmless) undervoltage can be measured with simple measuring devices. The (harmful) voltage spikes can only be measured with an oscilloscope or similar device.

Regards,
Guste.

In this specific case, I would disconnect the battery completely, charge it, reconnect it, and that should fix it.

...or simply try something different