battery hooked up backwards

[wstrnco]

I just picked up another liberty cheep,the guy hooked up the battery backwards.
It will only run on two back cylinders.
He replaced ecm&,fusable links I have checked codes all I get is oxy. sencers
I don't think thats the problem .I tried switching coils around ,changed fuel injectors,
no matter what I try it only runs on 2 back cyl. HELP PLEASE!!

 

[Cherrie]

Probably not related to battery, I wouldn't think you could even get the battery connected without it arcing. So much is drawing juice before you even turn the key.

 

[Billwill]

What year/model do you have?

Connecting the battery the wrong way around usually blows the fusible link in the thick wire going from the alternator to the battery, can also burn out some diodes in the alternator and could fry the PCM, TCM and BCM and Front Control Module in newer KJs.

Do you get a spark on the failing cylinders?
You need to check the wiring going to the coil packs from the PCM for continuity and no shorts and the same for the wiring going to the failing injectors.

If you have a short in the wiring going to the injectors or coils then replacing the PCM will simply immediately blow up the PCM in the same area....so you always need to check the wiring before replacing electronic modules. If the PCM has blown its transistors
in that area then it is probably incapable of reporting error codes for those circuits.

Here is a link to the wiring diagrams...download the Service manual for your year model KJ...includes the circuit diagrams. Use a Multimeter to check the wiring:

Index of /manuals/Jeep/KJ

 

[LKWJeeper]

If the battery was connected backwards just like billwill said it will blow a fuse and smoke.

Damn Auto Zone did this to my wife's car and all electronics and ignition didn't work till we replaced the blown fuse.

Check all the fuses and then go from there.

Sent from my LG-D801 using Tapatalk

 

[Cherrie]

Guess anything is possible. I would think that battery cables would arc when trying to hook up. Or battery would blow up. But I'm not gonna try it to see!

 

[tjkj2002]

Guess anything is possible. I would think that battery cables would arc when trying to hook up. Or battery would blow up. But I'm not gonna try it to see!

Shouldn't ark at all with all the modern electronics.A vehicle from say 20 years ago sure but not now.I've dealt with a few vehicles that the owners have hooked jumper cables up wrong,sometimes it just blows the main fuse and maybe 2-3 other fuses but does no other harm but sometimes it messes up the computers with "ghost" problems down the road.

 

[Cherrie]

Shouldn't ark at all with all the modern electronics.A vehicle from say 20 years ago sure but not now.I've dealt with a few vehicles that the owners have hooked jumper cables up wrong,sometimes it just blows the main fuse and maybe 2-3 other fuses but does no other harm but sometimes it messes up the computers with "ghost" problems down the road.

Um yep I'm old. I figured it would be just like welding. Still not going try it.
I'm still thinking OP has another problem.

 

[LibertyTC]

Shouldn't ark at all with all the modern electronics.A vehicle from say 20 years ago sure but not now.I've dealt with a few vehicles that the owners have hooked jumper cables up wrong,sometimes it just blows the main fuse and maybe 2-3 other fuses but does no other harm but sometimes it messes up the computers with "ghost" problems down the road.

^That is why it's time to consider upgrading your Jumper Cables to surge protected ones, that can automatically correct polarity themselves!
Link: Amazon.com: Michelin 5100 Smart Jumper Cables with Surge Protection: Automotive
I keep the smart jumpers under the rear seat. They work well when needed!
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[Cherrie]

"Smart" jumper cables, aren't those just for smart cars?.

I continued to read about hooking up a battery backwards. What I hadn't thought of until reading- most do it when jump starting, your Smart!