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The mkiv Supra Owners Club

Battery not charging/ poor earth fix


Marcus GTE

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I've been having a few issues with the car not wanting to start all the time over the last month or so.

 

Typically it would struggle to fire up in the morning, turning over very sluggishly.

 

Sometimes I would get rapid clicking like you get when the battery is flat, but it was very temprimental and I was in fear that if I drove it anywhere I'd get stranded.

 

After some searching on here everything from done batteries to starter motors and alternators being gubbed were suggested but poor earth was suggested a few times by multiple people.

 

To cut a long story short here is how I solved my problem so you can solve yours if you've done a search and find the same symptoms.

 

I had been doing some work removing the battery so I probbably upset the conection.

 

I noticed the terminals were pretty dirty looking so decided to clean them up.

image

 

Undo and remove the negative terminal first then before undoing the positive, loosten the top bolt that pinches the terminal to the earth plate/ wire then you can loosten and remove the positive terminal.

 

image

 

I gave it a quick clean with a cloth, and some steel wool with a light spray of wd 40. I did the same with the negative but didn't remove it. I also gave the battery pins a clean the same way.

 

image

 

The same goes for the plates that are on the positive side (remember to clean underneath)

image

 

After putting back together I made sure everything was done up nice and tight.

image

 

The only thing still to do is put some vastaline over the exposed positive and negative pins to protect them from contamination.

 

I've read this is an old practice due to older style batteries giving off vapour that can cause corrosion and eventually effect the conductivity of the conection; perhaps someone like Chris Wilson could advise on the corect practice here as I'm unsure.

 

I've noticed since the clean up the car starts first time like normal and seems to have fixed my problem :)

 

I also had a power coupling attached that I had no use for so I removed it incase it was causing an issue.

 

Can anyone say what I would use this for?

image

image

image

 

Cheers

 

Marcus

Edited by Marcus GTE (see edit history)
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Guest Roger NE

Well done mate . .

 

To be honest, I'm amazed that people don't do this on a regular basis . . . it's the first thing I always check if a car isn't turning over properly.

 

With a big engine like this the starter will be drawing about 200 amps when first cranking . . . if there was just a tenth of an ohm resistance on the terminals you would lose 20 volts . . but you only have 12 to start with! (get the idea?)

 

As well as the actual terminals on the battery, you also need to make sure the big current terminals going to the starter motor and alternator are equally clean and shiny, as well as the earth leads going to the engine block and the chassis.

 

Just like you have, you need to make sure the terminal AND the metal it's bolting to is nice and clean and dirt/rust/paint free.

 

I do this as a matter of course every couple of years on ANY car . . . I bet most Supras on here have NEVER had it done!

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. . . if there was just a tenth of an ohm resistance on the terminals you would lose 20 volts . . but you only have 12 to start with! (get the idea?)

 

It doesn't work quite like that but, yeah, using the figures in your example it would reduce the power going to the motor by over 90%

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Guest Roger NE
It doesn't work quite like that

 

Well I know that (I have an Electronics Degree) . . . I was trying to give a simple explanation that people could understand !

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R

Well done mate . .

 

To be honest, I'm amazed that people don't do this on a regular basis . . . it's the first thing I always check if a car isn't turning over properly.

 

With a big engine like this the starter will be drawing about 200 amps when first cranking . . . if there was just a tenth of an ohm resistance on the terminals you would lose 20 volts . . but you only have 12 to start with! (get the idea?)

 

As well as the actual terminals on the battery, you also need to make sure the big current terminals going to the starter motor and alternator are equally clean and shiny, as well as the earth leads going to the engine block and the chassis.

 

Just like you have, you need to make sure the terminal AND the metal it's bolting to is nice and clean and dirt/rust/paint free.

 

I do this as a matter of course every couple of years on ANY car . . . I bet most Supras on here have NEVER had it done!

 

Thanks for the contribution Roger. I've seen lots of threads with people having starting/ running problems which can potentially save hundreds of pounds on attempting a fix as I've read people buying batteries once a year etc. all this takes is a couple of hours of your time and although it might not sort everyone with similar problems to what I had its well worth trying before parting with cash.

 

I have an old shogun that was having the exact same problems with and I bet once I do the same procedure to it it will be fine. Makes me wonder if the new £200 alternator I bought for it was needed in the first place! Lesson learned.

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Guest Roger NE

Well the other thing people really ought to also do every couple of years is clean all the electrical connectors under the bonnet - as per my recent post on another thread

 

Plus people should replace their HT Leads every 6 - 7 years too

 

If people didn't neglect the electrics on their cars they would have far fewer problems !

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It's also worth cleaning the earthing straps between the engine lump and the body (on any older car), poor earthing causes a multitude of different (sometimes intermittent, the worst kind) probs once it is there, and you can't always see it just by looking at the connection, you need to undo it and examine properly or you may end up chasing your tail.

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Guest Roger NE

I already said that . . .

 

As well as the actual terminals on the battery, you also need to make sure the big current terminals going to the starter motor and alternator are equally clean and shiny, as well as the earth leads going to the engine block and the chassis.

 

Just like you have, you need to make sure the terminal AND the metal it's bolting to is nice and clean and dirt/rust/paint free.

 

And you're right Ian, a pointless waste of money buying an "Earthing Kit"!

 

If people cleaned up all their electrical connectors every 3/4 years there probably wouldn't be half the problems reported on here!

Edited by Roger NE (see edit history)
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