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One stupendously dumb mistake

3K views 31 replies 11 participants last post by  homestd 
#1 ·
Ok, So I bring my dead battery to Wally World to trade in for one that isn't dead. I have put a set of the 2-pack green & red felt battery terminal thingies with it as I have none. I am not really watching the guy closely when he open the pack and puts them on the battery. I get out and go straight home. Now, before the old battery died this Jeep, which had been sitting for over a year started right up and ran great.
So, I hook up the new battery I noticed a spark out the side with the starter, but there is no way I could see what is was because it happened quick...and was over. I disconnect the battery and after I have a look around hook the battery back up and now the horn is stuck on and so are the headlights. I'm thinking it is because it sat for so long. NOT! So I pull the fuse for it/them.
But now the starter just spins, but it doesn't turn the engine over. I try to jump it, but now this is when I noticed that the guy had put the colors of the velvet "washers" reversed!!!
So, I disconnect the battery, reverse those felt "washers" and start over.
Now the starter turns and it engages the engine, but no matter what...it will not start now.
1st Question: Any idea as to what the spark from the general vicinity of the starter was?
2nd Question: Will a diagnostic tool tell anything if the engine cannot start or is not running?
3rd Question: How do I trouble shoot what is happening?


Any help would be greatly appreciated!
Thanks!
 
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#2 ·
Did you check any fuses? Did you have any wires touch metal which would have caused it to spark? Look and see if you can get it jump started. I don't think those red and green washers would have caused any issue, as they just help with corrosion supposedly. I worked with a guy who thought his battery was bad so he got another one at the auto parts store. The car wouldn't start so he went back and cursed out the guy at the auto parts store, his girlfriend kicked over a display in the store. She was arrested, he was told never to go back in the store. Turns out a fuse was blown and after it was replaced, the car started. Strange but true story.
 
#3 ·
. . . I don't think those red and green washers would have caused any issue, as they just help with corrosion supposedly. . .
Unless, instead of looking at the terminal posts or the markings on the case, you rely on them for polarity & connect the battery the battery round the wrong way.

The starter might've survived going backwards (that's why it spun, without turning the engine) - but not so sure about the, albeit limited, electronics.
 
#5 ·
First, what Jeep are we working on, is it the 2000 XJ or something else?
I'll assume it's the XJ

Yes check the fuses, then check for spark, if no spark, then you have to diagnose the
ECU, crank/cam sensors there is a good chance one or all of these where damaged.
 
#6 ·
Ok, yes, I went by the color of the felt washers instead of the polarity makers on the battery itself. Me=idiot. I really can't believe i did that, but i did, no one else I can really blame which makes it even worse. :crying2:
Where it is now is that the engine was turning over great, but just would fire. I will be pulling and checking fused tomorrow. I am wondering if there are any fuseable links that I might have popped?
Damn shame this happened because even though I wasn't using it, it ran incredible. I had changed the head to one of the TUPY (?) heads as the old one finally cracked all the way.
 
#7 ·
fig-happens all the time to people. Last summer the battery in my Kawasaki street bike needed to be replaced. The terminals are the opposite on some model batteries. + on right, - on left, this one had the - on right and + on left. I hooked up the battery, hit start button and then heard a pop. A fuse was blown. Thank goodness I realized what I did, and went and got a battery with the terminals the correct way as the positive cable don't stretch on those. Lesson learned-bet its a fuse.
 
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#9 ·
I wouldn't have thought a fuse would care which way the current flowed through it - after all, they're not directional or relays (a common cause of XJ's not starting) for that matter & a starter's a tough old bit of kit & will survive some abuse but electronics are a very different matter. ECU, crank position sensor & cam position sensor are all different parts - & there are a few others.

A diagnostic tool must be able to pull codes even if the engine's not running, otherwise you couldn't diagnose non-starters.

There is a fusible link; it's the light green wire at the front of the underhood fusebox.
 
#19 ·
The fuse duzn't care, but the stuff connected to it sointily do. I would guess the PCM, alternator and those kinda thingys don't like to be reversed. As for the starter, there is always a residual current flowing in the field, and possibly in the armature . When you reversed the polarity, you could get a spark.
 
#10 ·
I would be concerned about that spark the OP said came out by the starter. Look for burn marks by the starter. I think they can be tested at an auto zone or good auto part stores. OP fig did you crank it over several times before you saw the mistake? If so could have damaged more things but still saying fuse, or now fusible link or starter.
 
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#12 ·
Oh yes, I cranked it quite a few times as I still had no idea the thing was reversed and not even suspecting that. It was actually one of those small jump started devices that tipped me off. It had a constant beeping sound which was a code for it being improperly connected. It looked right to me, but when I looked more closely I discovered my dumb@$$ mistake. As I go through the discovery process I'll provide an update or updates. Who knows, maybe I'll get lucky!
 
#13 ·
My younger brother(53) always wanted to help me on my vehicles. One day while working on my XJ, he took a brand new Snap On wrench and dropped it by the battery. I saw sparks and the wrench actually split in half. After removing it with welding gloves, battery simply worked after I cleaned up everything. I have also used batteries to weld things-kind of scary but gets the job done.
 
#14 ·
OP stated the engine now turns over with the battery connected correctly.

Again, check for spark at the plug. Is there spark when then engine turns over?
Electronics do not like to be connected backwards, I believe the ECM may be fried.

As for the spark at the starter, it should be fine as it turns the engine over now.
 
#15 ·
and one positive from all this, fig, is that you will never mis-wire a battery again. i know, i have done it also and one time was all it took to make sure it never happened again
 
#17 ·
I always thought that battery posts were different sizes so (a) you can tell at a glance which is which (b) it's difficult, if not impossible, to make that mistake - although at different times Ford and GM have decided it was an unnecessary precaution/complication/expense. (& I believe the Japanese don't consider the difference needs to be so obvious)
 
#18 ·
The OP said after I asked him, that he cranked on it several times. That will kill other things besides fuses. Lesson learned the hard way. I have seen people hook up batteries wrong with disastrous results.
 
#21 ·
UkXJ-Since you want to doubt me every time, then why wont this vehicle start? I have had vehicles pop a fuse when you hook up the vehicle backwards. Motorcycles will do that too. The OP didn't say originally in his 1st post he cranked on it several times.
 
#24 ·
Yep it takes a diode to make for directional current, like an alternator diode to prevent backfeed.
 
#26 ·
Obviously my simple statement was misunderstood by those that know (far) more about such things than I. Of course I know a dead short will blow a fuse, that's its purpose, but I never mentioned a short, just the fact of the current passing through a fuse the wrong way.

Now, please explain this for me, if (as I was not alone in failing to appreciate) the ECU, e.g., was protected by the diode causing the fuse to blow, once the battery had been reconnected correctly - & the fuse replaced, why won't the Jeep start?
 
#28 ·
Obviously my simple statement was misunderstood by those that know (far) more about such things than I. Of course I know a dead short will blow a fuse, that's its purpose, but I never mentioned a short, just the fact of the current passing through a fuse the wrong way.

Now, please explain this for me, if (as I was not alone in failing to appreciate) the ECU, e.g., was protected by the diode causing the fuse to blow, once the battery had been reconnected correctly - & the fuse replaced, why won't the Jeep start?
How do we know that it didn't? The OP hasn't posted back yet with further information. Not only have you apparently re-written the laws of electrical current flow, you also read minds now? If not, please enlighten us humble masses as to how you know that it won't start with a new fuse, since the OP hasn't posted that information.

Its also possible that just replacing a fuse won't fix it; the damage may go further than that, or it may not. If the ECU has a polarity protection diode, the diode may have catastrophically failed while the fuse was blowing, damaging the circuitry. Reverse polarity can by like a lightening strike, in that it may damage nothing, or one component, or trash everything. You were correct before, in that this may have damaged the crank/cam position sensors, or the ECM. You just appear to be lost as to how electrical/electronics work. We all knew that you didn't mention a short, just that you were confused as to "how reverse current can blow a fuse", clearly illustrating that you are clueless. A short caused by the reverse current can blow a fuse. Thats how current flow works. You should learn to ask questions when you don't know, instead of arguing with those that have more knowledge/experience than you.
 
#29 ·
I only agreed with the statement that a fuse is non-directional so the mere fact of current flowing through it wouldn't cause it to blow, I hadn't thought beyond that because that is the extent of my knowledge - or was because, obviously, I know a little more now.
I didn't even know there were "laws of electrical current flow" (although I may be familiar with the principle - but not by that name) so I could hardly presume to re-write them & far from being psychic, the way I looked at it was, we've not been told it will start, so we work on the basis of last available information, i.e. it won't start but I was wrong to state " . . . & the fuse replaced . . . " although I believed that to be the case at the time.
My long experience of auto electrics is at the simplest battery- switch-(relay)-component-ground level* & electronics are a black art: I have never pretended otherwise although always prepared to learn (but not to be insulted). That is why I have never consciously argued, or even disagreed, with anyone, as it's unlikely I'm in a position to. As I have no wish to irritate/upset those who clearly know more than I, or to offend their sensitivities, I will bow out of this discussion altogether, lest I be tempted to, ill-advisedly, participate again.
* no I haven't forgotten fuses (not because my 1st car didn't have any) it's just that they don't conveniently fall into a fixed position in this circuit.
 
#31 ·
I quite understand where you are coming from. Don't misunderstand my intentions. Yes, I was a bit abrasive, but only after you kept arguing with others about how "reverse current can't blow a fuse". You are correct, in that reverse current itself won't blow a fuse, but electronics can act very strangely when connected backward, including a dead short. Sorry about my earlier attitude, but it just really irritated me when you kept arguing with everyone else. Please, if you have any questions about how all this stuff works, feel free to ask, and I'll do my best to (without an attitude) explain it to you. Cheers!
 
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