Cross posting from V6 Technical : Battery cable replacement

neumann · Post by **neumann** » March 26th, 2007, 2:01 pm

Sorry if this is poor etiquette but am cross posting this form the V6 Technical/Performance Forum:
http://www.mx-3.com/phpbb2/viewtopic.php?t=58158

I have to change out the negative battery cable in my 1994 GS manual transmission. It finally went spectacularly bad. The Positive cable is okay but I am replacing the positive terminal. Ironically I had the parts already but was just hoping to do the work after I store the car for the summer. Unfortunately I have to get the car emission tested in the next two weeks.

I am a mechanical idiot so this may seem totally obvious, but where does the negative cable connect? All of the wiring is routed through conduits and wire loom and covered in filth so I am trying to do this while disturbing as little as possible other stuff.

One of the battery cables appears to be connected to the starter like the figure on page G-035 in the OSM, but my rank idiocy and fear of fireworks leads me to not want to test the probabilities.

Any help appreciated

PATDIESEL · Post by **PATDIESEL** » March 26th, 2007, 10:10 pm

I know it will be a dirty job, call Mike Rowe. LOL
Really, take the cable out of the conduit by "carefully" splitting the conduit with a sharp razor. Then, ONE AT A TIME, replace the cables the same way the OEM ones were ran. It is the safest, easiest way to make sure the job is done right. Make sure to buy the proper ends to hook the cable back up the starter, battery, ground points so that you don't get stuck with no cables and no way to the store to get what you need. Make sure to soldier the cables into the connectors so that you get a good solid connection. If the connection is bad the car might start and seem to run fine, but you'll be frying every thing they are connected to b/c the electricity cannot run smoothly.

justin22_22 · Post by **justin22_22** » March 26th, 2007, 10:35 pm

don't solder the wires, it breaks them down. I'm an electrician, not going by what I heard from a friends friend. Just make sure you crimp them good, and use the right size.

PATDIESEL · Post by **PATDIESEL** » March 27th, 2007, 1:17 am

So was I, and I've never heard that before. I don't think you are going to break down a wire that size with the heat needed to melt soldier. I understand that you are saying it would aneal (sp?) the metal, which is basically metal fatigue, but you need more heat than a quick torching can provide.
Anyway, do as you like. I soldier every wire and have never had an issue. However, I've seen plenty that weren't soldiered that either come loose or have a poor contact.

neumann · Post by **neumann** » April 2nd, 2007, 1:47 am

Okay, so I took the conduit apart and traced the negative battery cable down to a ground point on the engine block. It also has a ground to chassis up near the engine mount which appears to just be a stripped area of the cable with a copper connector crimped on.

When I was at the store, I didn't see any cables with this configuration. I did see short cables and various combinations of cables ending in simple attachment points or terminal post connections.

Is there an actual cable with the chassis ground?

If not can I just strip an area of wire and find some type of conductive crimp on connector?

Should I just attach one cable from the negative battery post to the chassis ground and another cable from the same chassis point to the engine block?

PATDIESEL · Post by **PATDIESEL** » April 2nd, 2007, 9:19 am

A normal negative cable should be run from the battery to the chasis. Any other grounds that are also connected can be run using a similar to stock size stereo wire. The crimp on ends can be bought at most any stereo shop or parts store as well as upgraded battery terminals if needed. I usually buy the type replacement cables that have the battery terminals that bolt the wire down and are NOT crimped. This is so that you can mess with the wires and then reattach them instead of having to buy new battery terminals. On the ends where the cable attaches to the starter, fuse box, and ground points make sure to use a good crimping connection. Loose or bad crimps will result in failure of one or more parts.

neumann · Post by **neumann** » April 2nd, 2007, 9:59 am

Thanks Pat, great info as always. You really are a valued resource.

The cable that i have for negative battery has bolt on connections at each end, with the battery side bolted to post terminal connector things. I initially have bolted the other end to the engine block where the original cable ended.

I have not yet re installed the battery, but I figured I would face three choices:

1. Using parts I have. Connect battery cable from the negative to chassis via bolt on the other end. Connect the same point via bolting another spare battery cable and terminating bolted to the engine.
Cons: Not sure if the two cables bolted together through the bolt holes in the ends at the chassis point would maintain a solid contact?

2. Buy some type of bolt on connector and strip a section of wire to ground to chassis, on its way to end at the engine block. This appears how the original was done.
Cons: Stripping a section of the negative battery cable.

3. Try and fine a cable with a mid point ground already built in.
Cons: Have not seen this part.

PATDIESEL · Post by **PATDIESEL** » April 2nd, 2007, 4:44 pm

I think that I ran two seperate wires. One from the battery to the engine (acutally I think it is connected the trans, but just go with that the factory did). Then from there to the chasis ground near the window corner. I used O ring connectors at the engine and chasis grounds to make sure everything stayed put. Make sure to clean the spots where it grounds to. The threads and bolt are not the connection, the pinch between the connector and the metal of the engine or frame is where the grounding acutally happens.

neumann · Post by **neumann** » April 3rd, 2007, 6:04 pm

On my way home last night I stopped at the store. They had a grounding strap with copper core bolt holes at either end and it looked juuuust long enough to span between the negative battery post and the contact point for the chassis ground.

At home I installed and it started up fine, idled it for a while. This morning I decided to drive the car to work. About a mile from home it stalled repeatedly. I pulled over to the side and looked under the hood. The new negative battery cable was kinda loose at the post. I think what had happened is that the ground strap attaching at that end had chewed up just enough space that it prevented the nut from being screwed on all that much and it shook itself loose. I grabbed a ratchet out of the back and cranked it down as hard as I could.

I pulled out the portable battery booster thing I have that plugs in the cigarette lighter. After about 20 minutes it turned over but would not start. After another 10 minutes it started and so I drove it home to switch cars. I am going to charge the battery tonight and see how she is in the morning.

PATDIESEL · Post by **PATDIESEL** » April 4th, 2007, 2:45 am

Make sure that cable has some looseness to it. The motor moves more than you would think. It will need some slack so that it doesn't pull on the connection points. You should consider putting a second grounding strap on the passanger side too. The MX is not grounded very well and I have seen many members post about improved performance from adding a ground or two.

neumann · Post by **neumann** » April 4th, 2007, 3:42 pm

Pat

Yeah, I will get another ground cable. The one I got for the chassis ground is like a ribbon cable with about an inch and a half of slack. I have connected it to the terminal connector attached to the negative post.

There is a fair amount of slack on that cable which is 4 gauge which is bolted to the transmission housing (you were correct)

I was just happy it was running this morning. It idled fine, although on my way to work it was running a little rough on acceleration. I assumed it is not in limp mode, no CEL light is on.

Is there a period of time after pulling the battery that the ECU takes to re-set itself? On one of my other cars, it would always drive like a piece of crap for about 5 minutes after the battery had been re-attached. I drove the car about 20 miles this morning on my commute and it just seemed as though it stumbled a bit accelerating from low RPMs in low gears and also did not rev as freely in 4th or 5th

Do you think the quality of the chassis ground cable or its contact points could causing rough engine performance? Could I have damaged something electrical that causes this?

I am going to check my intake for air leaks, which I expect could cause the roughness accelerating from idle. Anything else to look for?

I would not be too urgent on this except for the fact that I need to get the car emissions tested in the next three weeks.

PATDIESEL · Post by **PATDIESEL** » April 5th, 2007, 12:45 am

I don't mind helping at all.
It could be either intake leaks, ground connections or the power connections. Do a double check of the power connections and all the cable ends. Make sure they are tight. Tug on the wire a bit and if it starts to slide out of the connector it needs to be redone. The ground points need to be cleaned and then wire brushed to make sure they have a good clean metal to metal contact with no corrosion. This inclused bare metal like the trans. Aluminum does oxidize, so make sure it is clean. I also use di-electrode (sp?) grease on the ground connections. The grease will permit a strong elec. current to pass through and keep the contact surface from oxidizing. If you haven't messed with the intake I would not bother with it much more than a decent check.
To reset the ECU of codes and clear limp mode if it has gone to that- remove the positive battery cable, press the brake pedal for 15 seconds and then reconnect the postive cable. The ECU doesn't store much power and using the brake pedal turns on the brake lights which will eat any remaining power in the system and reset the ECU. However, from what I know there must be a stored code for limp mode to stay on. Therefore you should have a CEL light if in limp mode, but it is still worth a shot.

neumann · Post by **neumann** » April 5th, 2007, 10:35 am

Thanks Pat

I was worried that is was the distributor which I hear is a known weakness on these cars, but I likewise assumed that if it was missing a cylinder or something I would get a CEL.

The CEL has always appeared to function as I have seen it and pulled codes for O2 sensors and Crank Position Sensors and replaced both.

I will recheck the connections and maybe replace the positive cable too. I bought the part. The connections to the battery appear solid. On the other side they are tight but could be dirty. I was planning on getting a better ground strap anyhow.

I think there is a hairline crack on some air intake tubing which I will check for.

The car appears to be idling a little lower than normal at temp (maybe about 700 RPM when before it seemed more like 850?) and the hesitation appears to be between idle and about 2500 RPM. It is intermittent, which I figured was less likely to be disty and more likely the things you suggest.

In high gears there seemed to be an occasional stumble above 4000 RPM, (eg when highway passing in 4th gear) although again inconsistent and I was able the rev to 6000 in 2nd gear effortlessly.