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Engine Smoking when Battery Connected


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smokingengine
New User

Oct 1, 2016, 10:15 PM

Post #1 of 10 (1875 views)
Engine Smoking when Battery Connected Sign In

1995 Jeep Cherokee 4.0L

The battery was dead so I hooked up another car for a jump. The car started, but would die the second the cables to the other car were disconnected.

Tried leaving the car running while connected for 20 minutes or so with the engine running in the hopes of charging the dead battery, but the battery was too far gone and a write off. At the end of this, something in my car engine started smoking very slightly, just a faint smell like burning plastic but no visible smoke.

Bought a new battery and hooked it up. Hooked it up properly, didn't reverse the polarity or anything.

But when the battery is fully connected, something starts immediately smoking quite heavily. Dark smoke, toxic burning plastic smell.

I welcome theories as to what part the smoke is coming from and next steps.

Thanks for taking the time.


Tom Greenleaf
Ultimate Carjunky / Moderator
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Oct 2, 2016, 1:37 AM

Post #2 of 10 (1864 views)
Re: Engine Smoking when Battery Connected Sign In

EeeK! When a battery is that dead that a vehicle would stall with cable removed the alternators of both probably were working WAY TOO hard to charge the impossibly dead battery.


Late now but probably see evidence at the Jeep's alternator and wiring.


I'll strongly suggest jumping vehicles be left to jumper boxes or to a charged battery which they are not involving another vehicle. If unknown or known why a battery is low or dead meaning zero activity it really has to be checked out and charged or risk a string of new problems possible,


T



Discretesignals
Ultimate Carjunky / Moderator
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Oct 2, 2016, 9:07 AM

Post #3 of 10 (1856 views)
Re: Engine Smoking when Battery Connected Sign In

Let me get this right, you left both vehicles running for a long period of time with their charging systems connected together? If so, that is not definitely not smart. The Jeep has EVR built into the engine controller and was probably sensing the other vehicles charging system along with its own dead battery. I can see how it would fry EVRs or even the field in the alternator.


You should do a really good visual inspection before going bananas with connecting up power to it again. Use your nose to see if you can find the source of the burning. Last think you need is an electrical fire. Believe me, vehicle electrical fires are no joke.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Oct 2, 2016, 9:16 AM)


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Oct 2, 2016, 11:34 AM

Post #4 of 10 (1845 views)
Re: Engine Smoking when Battery Connected Sign In

This vehicle is almost certainly going to be a real pest and pricey to fix.


Just suggest you check the donor car now and without messing it up see if it's charging system is even putting out more that 12.6V when running. If that car was trying to charge what seems like now dead short it could have problems,


T



smokingengine
New User

Oct 6, 2016, 5:37 PM

Post #5 of 10 (1821 views)
Re: Engine Smoking when Battery Connected Sign In

Well, I won't pretend that what I did was intelligent.

That was a rule I had never been told - don't keep a jump going longer than a few seconds.

Can anyone tell me what the likeliest parts are for potential damage here beyond my alternator?


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Oct 6, 2016, 6:29 PM

Post #6 of 10 (1819 views)
Re: Engine Smoking when Battery Connected Sign In

Did you find the source of the smoke? Does your alternator smell like burnt wires?





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


smokingengine
New User

Oct 7, 2016, 10:39 PM

Post #7 of 10 (1801 views)
Re: Engine Smoking when Battery Connected Sign In

As it stands, nothing else visibly looks like a candidate for damage. Had to do some cleaning on the undercarriage to inspect cables, parts and wiring and burnt smell has pretty much dissipated. Looking into the alternator from outside through the slots, it looks like the wiring inside may have undergone some blackening or melting.


Hammer Time
Ultimate Carjunky / Moderator
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Oct 8, 2016, 4:55 AM

Post #8 of 10 (1796 views)
Re: Engine Smoking when Battery Connected Sign In

If that's the case, the alternator will smell burnt.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



smokingengine
New User

Oct 12, 2016, 2:49 AM

Post #9 of 10 (1771 views)
Re: Engine Smoking when Battery Connected Sign In

I haven't been able to smell burning from the alternator, though I haven't removed it for close inspection and can't get right up to it while it is in place, so I am sniffing at it from a slight distance.

In retrospect, I THINK the smoking happened only when the battery was connected AND the engine was actually running.

Thoughts on how this affects the diagnosis?


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Oct 12, 2016, 4:37 AM

Post #10 of 10 (1767 views)
Re: Engine Smoking when Battery Connected Sign In

Of course it only smoked when the battery was connected but whatever burnt at that time is still burnt and will still have an odor.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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