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The mkiv Supra Owners Club

Car wont start, and its not the battery!


Sean1933

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I started the car up this morning no problem and drove to work.

 

Got to my car tonight, disarmed with key fob, and turn key to ignition, dash lights up as normal. As soon as i turn it to start everything cuts out. Now there is no dash lights or anything...its like a massive short curcuit.

 

Jumpstart the car and everythings fires straight up. Drive home and park on driveway...turn off and back to ignition and everything is lit up as normal...turn to start and the everything goes out and its now dead as a dodo again...WHAT THE HELL!!! Then i think fuck it and go in my house, 2 secs later the alarm goes off! So i go out and turn it off, battery is dead again.

 

Only things i have done recently is fit HID conversion 3/4 days ago which is simple..and i had the g/box out last weekend to change the clutch...

 

Ideas on a post card please! :search:

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My reasons for not thinking its the battery is because it powers everything fine until you try to crank it, then its dead. If it was the battery wouldnt it just click as not enough power to crank. Its not like the lights go dim when i try to crank...it all just turns off straight away!

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nope never had the problem before. Just jump started the car and then disconected jump leads and managed to crank the engine 3/4 times just of the battery. didnt seem really strong but still started. Took the battery to halfrauds and they checked it, good battery it said! :( I left it with them and am going back tomoz morning to check again to see if it held the charge.

 

Is there anyway to check the alternator is working properly?

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Well when i jump started it i only conected the positive and it started up fine. MY worry is could it be the alternator which are expensive!!! How can i check?

 

You only connected up the positive? you must have had a lead going body to body at the very least.

 

It is sound more like a grounding strap issue. You say you changed the clutch, did you make sure you connected back up all the grounding straps. I believe there is one on the clutch bellhousing.

 

Easiest way to check, use a single jumper lead and connect the negative pole of the battery (make sure only the negative) and somewhere on the engine together.

 

Then try start it.

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Im sure i connected the bellhousing one back up, but i will go check.

 

When i say i only connected the positive i meant from the other car. Battery was still connected so it would have been grounding as normal.

 

I checked the voltage of battery when running and it was approx 14v...that says to me its charging. Anyone disagree?

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When i say i only connected the positive i meant from the other car. Battery was still connected so it would have been grounding as normal.
You only connected one jump lead (the positive) between the two cars? I wouldn't have thought that would work.

 

I checked the voltage of battery when running and it was approx 14v...that says to me its charging. Anyone disagree?
It shows the altenator is making power to charge the battery ok, it doesn't prove that the battery is taking the charge though.

 

Do you have another battery you can try on the Supe?

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yep only connected one lead. I was abit miffed. but both batteries (in each car) were grounded so i can see why it would work. doesnt have to be grounded to the thing it is powering.

 

Im glad the alternator is working, not too worried about getting a new battery just didnt want to need a new alternator...£££

 

Going back to halfrauds in a bit to retest the battery...if they say its fine then im really confused. Going to try another battery now...watch this space.

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why did it start then!!???

 

Just got back from halfrauds...they said the battery is fine. I brought it home, car started fine. Just got bac kfrom a long drive and tried to start it up...started fine.

 

I want to know why it wouldnt start, batteries dont just die for no reason!

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Yes they do, I've had loads of batteries fail on various different cars.

 

Check the voltage across the battery on its own, should e around 12v

 

Get someone to crank the engine while you measure the voltage, shouldn't drop below 10v

 

As mentioned, with th 14v when running it shows that the alternator is fine.

 

A bad battery can show good voltages on its own and under charge but show up any problems when cranking - I had this on an old AX; the battery seemed fine until the engine was turned over, when it only gave out 6v!

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Guest gzaerojon

my money is on a dodgy corroded or loose battery terminal, remove them and give them a good clean with a wire brush or sand paper. When you turn on the ignition it will all light up with a poor connection but as soon as you crank it, the extra current draw will lose the circuit. I'm pretty sure you disturbed the connections with the jump leads, hence it started, and there's no way you can jump start a car with just 1 lead, it's impossible

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Guest gzaerojon

also just to ad, make sure the sidelights are switched on when you re connect the battery, if you get a spike it will save your ECU from blowing :)

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