Bad ground symptoms?

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Thread: Bad ground symptoms?

  1. #1
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    Bad ground symptoms?

    Hi guys

    OK so Ive posted something similar before but still no resolution. Was going to attempt to let the autoelec take care of this in between the r154 conversion but thats a bit delayed so thought Id tackle this on my own so I can at least start my car without the help of another. too scared to even run the brand new engine in as it needs a tune so it stalls in first gear and I cant get it started again due to this problem.

    I can only ever start my car if its boosted by another running car.

    Symptoms : When I turn the key it clicks (not fast rapid clicking like a bad battery connection , just clicking )

    I replaced the starter with a freshly rebuilt one.

    I have tried the 30A relay mod, didn't seem to make much of a difference

    Left the car overnight connected to the battery:

    Reading when i turned the car off :11.7 V

    Reading the next morning : 7.7 volts.

    It seems as if I have something draining my battery .

    In saying that, after I starter the car with the help of another car , and drove around for half an hour , and then switch it off and immediately try to start again all I hear is the click. Shouldn't the alternator have charged the battery enough to at least start the car immediately after it was shut off.

    Before I take my car to the autoelec I was wondering if these are symptoms of having a bad ground?

    Theres a thick black wire connected to the inside of the engine bay with the other end connected to nothing. Would anyone know what this black wire is supposed to be connected to. Ground maybe?

    Lastly, does anyone have an overall diagram of all the parts of the 7mgte and the electrical connections.

    Yes I have the TSRM , just looking for something a bit clearer and a bit more detailed - what each part is etc, where each wire should go etc.

    Oh and I posted this on two other sites in the hope of getting a wider range of responses,I'm sure some will flame because of this , why...I don't know.

    Anyway any help is appreciated, thanks in advance guys

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  3. #2
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    Remove battery and have tested at a auto parts store
    If the health and CCA rating is close to spec then do a parastitic draw test
    If ya don't know what that is then Google it
    Sry I'm on my phone and can't provide a link

    You can have a perfect voltage of 12.6 at the battery all you want
    But what really plays a big role is the CA and CCA
    Those pretty much mean how much amps the battery can put out for a certain amount of time
    Say your 650cca battery actually only has 100cca due to low health
    When you apply let's say 100 amp draw from the starter
    The amps the battery have available is not enough to provide the 100amp the starter is requesting over a given period

    87 turbo supra 5spd targa
    09 corolla

  4. #3
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    Quote Originally Posted by jonahs_supra View Post
    Remove battery and have tested at a auto parts store
    If the health and CCA rating is close to spec then do a parastitic draw test
    If ya don't know what that is then Google it
    Sry I'm on my phone and can't provide a link

    You can have a perfect voltage of 12.6 at the battery all you want
    But what really plays a big role is the CA and CCA
    Those pretty much mean how much amps the battery can put out for a certain amount of time
    Say your 650cca battery actually only has 100cca due to low health
    When you apply let's say 100 amp draw from the starter
    The amps the battery have available is not enough to provide the 100amp the starter is requesting over a given period
    put your big black wire back on,it should go from body to engine block.no main earth can cause your symptom. then follow above. if you realy get stuck PM me and we'll sort something out.

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    Quote Originally Posted by aloshan View Post
    Theres a thick black wire connected to the inside of the engine bay with the other end connected to nothing. Would anyone know what this black wire is supposed to be connected to. Ground maybe?
    If you are referring to a thick (not as thick as main ground) black wire on LHS fender near the igniter. I believe is should also lead up to –batt post.
    There are lots of pictures of stock Supra “under-hoods”
    Just do a “google image search”

    Quote Originally Posted by aloshan View Post
    Lastly, does anyone have an overall diagram of all the parts of the 7mgte and the electrical connections.
    The following link is the most complete diagram I have found online:

    http://www.cygnusx1.net/Supra/Librar...px?S=Main&P=35

    Also, i am new here and am still learning all these HTML reply codes that are visible on my screen here. Sorry if this message is bold, blue, moving, italic, or upside-down

  6. #5
    Moderator SideWinderGX's Avatar
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    The alternate sounds fine if you drove around with no problems. Might be a bad battery that just can't hold a charge, go have it tested like someone else said.

    That being said, checking and replacing your grounds is a really good idea, I would do it.

  7. #6
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    seems to be a bad ground + massive parastic drain from somewhere( i can literally see the volts drop by 0.1 on my multimeter with the car switched completely off). Im just going to send it to the auto elec and get the wiring done brand new from the ground up.at least that way I have peace of mind. oh btw , this is the black wire that isnt connected to anything I was talking about :


  8. #7

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    I would definetely reccommend getting the schematic and checking gnd points etc, which the wire in the above picture looks like a chassis gnd. Without that chassis gnd many electrical issues become possible hook the earth gnd back up then recheck. Id also check your block gnd, and get rid of those terrible cable ends!

    If you have DVOM you can check your resistances to ground by simply poking the test lead into the post and other on the block and then on the fender to ensure the whole car is grounded.
    Also if you pull your battery and charge the battery and it doesnt recover to at least 12.4 outside the car after charge then the battery is toast, which you can also check using DVOM(Digital Volt and Ohm Meter)

    Just remember though batteries themselves can be parastic draws because they have 6 cells, if one cell is toast it will discharge the other 5.

    If none of this helps shoot back and Ill explain how to do a parastic draw check, Hope this helps you out.
    Last edited by Bigtimr; 10-16-2011 at 02:42 AM.

  9. #8
    Moderator SideWinderGX's Avatar
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    That is a chassis ground. Its not in the same spot as mine but doesn't matter.

    It sounds like a parasitic drain but bad batteries will do the same thing. You can charge them up and they will discharge as the chemical reaction inside the cells reverses because of a leak or something. Go try a new battery before you do anything, and get a new wire for that chassis ground and I'd say you're good.

    Only way to tell if its a parasitic drain is to test the current flow when the car is off and make sure it isn't anything more than a few milliamps.

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