Issue connecting battery

Recently got my 2007 Speed 6 back after shop states the engine I paid them to install was knocking, so wanted to get the battery hooked up and hearing the issue myself.

I picked up a size 35 battery from Costco and went to hook up the battery terminals and sparks begin flying to the point that the battery posts started melting. I know it was correct posts, positive on the left and negative on the right. I admit I put on the positive second, but I've done this on other vehicles without issue. So I started again installing the positive first and then the negative and the same thing happened on the opposite side with the negative post sparking and melting a bit (positive side is left and negative was right nearest to the firewall).

I will say I thought the shop I took the engine to was reputable until I experienced the amount of time they had the vehicle, lack of service, and professionalism they showed. Heck, they disconnected the steering column and didn't even put it back before returning the vehicle so I'm under the impression something isn't hooked back up. Does anyone have an idea as to why this would be happening by just installing the battery cables? Before they received the vehicle it had been sitting at least two years. So now I'm figuring I should check over all the fuses, check that they installed the grounds back, and a friend mentioned checking the starter wiring. Unfortunately, I am horrible in regards to wiring, but I'm capable enough to check over all the wiring. And wondering if anyone else has experienced this issue.

Unfortunately, before purchasing this vehicle I didn't do enough research, now I'm in search of a Helms workshop manual for the vehicle to do a better and more thorough check to find the potential issue. I have searched on various forums and everyone else's issue was related to reversing their cables which doesn't match to my issue.

Any help is appreciated. Post didn't need to be this long.
EDIT: And probably should be moved to Troubleshooting instead

 

You are going to need a qualified helper. Manual will be a requirement to help you troubleshoot. Your description of sparks flying means you need to visualize..... everything... Sorry if this seems like no help. Your issue sounds like the previous "mechanic" was really incompetent. So nothing can be trusted, which is different than a vehicle that was working fine and a failure occurred.
My best advice is you need to find a reputable shop and spend $$ sad to say.

 

Thanks for the honest feedback, for some reason it was hard enough to get a shop here that would even install a JDM engine. So I'm going to at least wait until I can get a manual in to make sure everything is in order before I attempt to go that route again. After paying for their "work" I'm not in a hurry to give someone else a bundle so quickly.

 

Sounds like some warn cables somewhere or something's loose. Definitely worth staying with inspecting the main battery harness something could easily be off there if it got pinched during an install.

We have the shop manuals and writing diagram available in our metal member section, becomes available after website donation, funds keep the lights on here and we also have monthly raffles for members typically 1-2 50$ gift cards for vendors of the site

 

I actually have the shop manual on my computer that I located online, however I am one of those weird types that still buys physical books/finds it easier to browse vs scrolling on a computer due to the sheer number of pages. But maybe I'll head there for the wire diagram then. Once I start to get dirty with this car, hopefully I'll begin to feel comfortable enough to deal with more complex wiring.

 

The shop fucked something up with the power cables.

I've never experienced this, but have friends who have had this happen on other cars.

Follow your grounds, and follow the hot cables. Make sure they didn't hook up a hot cable like a ground, or a ground to where a hot cable should be (fuse box, alternator, etc).

Regardless of the battery size, terminals shouldn't get hot, or melt, or any of that.

 

Why did they disconnect the steering column etc? When I replaced the engine in my car I pulled the whole front end off and took it out that way. The suspension was never disassembled. To get the axles out I just loosened the ball joint and pulled the spindle away from the axle to get it out.

If you haven't fixed what they've messed up I suggest you take lots of pictures and document everything you find wrong. Then take them to small claims court. You paid for a service and they failed to provide you with an adequate repair.

 

Check the polarity of the battery as well. I've seen them reversed before.

 

That was my thought as well, which is what was leading me in this direction before doing anything.

Why didn't they reinstall it? Why is the little over radio compartment now broken?
Why did they take all the oily and grimy spare parts and put them in the backseat when the trunk was completely empty?

I had questions about a number of things after the fact. Completion date was supposed to be by the end of March. I didn't get a call, voicemail, or message from them. I stopped in the shop near the end of May and was informed they were having issues getting it started and throwing a crank position code after having to get new wiring for the crank position connection (unknown issue to me). But even after my check in, they went radio silent again until I reached out 30 days later only for them to tell me I had problems with my motor (July 5th). Dropped off the car and had the engine delivered in January.

I've pulled engines before just not a Mazda, but I've never needed to pull the steering column so your guess is as good as mine. I figured they dropped the subframe and pulled from the bottom because they had it on the lift. I did take a picture of the battery I took back as I wasn't even certain it was the brand new one I gave them. But subconsciously I was probably going to snap pics as I already have plans to check over all the new OEM parts I purchased to go in with the install (ignitors, fuel injectors, clutch kit with both bearings, water pump, serp belt, and Fidanza flywheel).

I did see that mentioned in a search, cannot recall forum but I thought that would have been odd. But yes, I can check that out too.

 

Looks like I have the Workshop and Wiring Diagrams coming. Delivery says Saturday but I'm figuring Monday.