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Brand new to the forum and I have a question about a 2008 GT Speed that I cannot get started and have run out of ideas. I have started a number of these cars as my friend is a dealer and uses my big driveway as a temporary sport to leave cars now and then. This 2008 GT Speed was brought to my place and left for a long time. Had run fine until it was parked. I now want to get it started and started my journey down this rabbit hole .. At least the key works on this door with a dead battery. I was able to open the hood and use a little power pack on the terminals in the engine bay bay to get enough power to open the trunk.. Part 1 - success. I see the two batteries.. (Small for starter, large for other electrical).. I put a meter on the small batt and it's giving off 12.3V (around).. the large battery is pretty much dead.. (2-3V).. I put a booster on the large battery and waited a bit and jumped in the car. I get the onscreen display.. lights work.. everything is bright and looks good.. I turn the key (right).. and nothing... I try the left then right trick to switch batteries.. nothing.. I checked the connectors on the small battery and everything looks fine.. I even borrowed a brand new (large) battery and still nothing... I then used my own car with cables as the source and did get the "Clunk" sound on the emergency key turn which tells me there is power and the battery is switching.. but nothing from the engine.. I recall a while back getting a slight "grunt" from the starter but this was a while back.. I checked the fuses in the back battery area.. and around the steering column which all look fine.. Short of towing this car away.. does anyone have another idea or trick I can try to get this beast running?
Hello Dave. What is the mileage on the car? The described Clunk is that the starter solenoid Clunking indicating a possible failed starter or locked-up engine. Have tested for codes?
Ron
Thanks for the reply. The car has about 50K. and I should have mentioned the "Clunk" sounds was from the trunk which I believe is a relay which will switch from the starter or the starter and large battery when doing the counter clockwise turn with the key. I am pretty sure the engine is fine. When I parked it, I was starting the car every week or so just to keep the battery charged but left of business and the car sat for several weeks. Small battery seems to be fine (just over 12V).. large left battery is around 3V.. Later today I am going to try and jump the car per the manual.. using + from the small battery and - from the large battery and see how it goes. When I put a charger pack on the large battery its wierd.. everything lights up... doors windows lights and console all work as you would expect .. but turning the key (left or right) does nothing
Hello @fishbone ,
Just a heads-up, the emergency start of turning the key counter clockwise does not switch it from one battery or the other, other a parallel solenoid, therefore putting both batteries in parallel, so if either battery is super low, it will be a strain on the other battery, which is most likely low also, just not as low, also, I would not attempt to many more starter tries with low power as you risk burning out the starter, which is an engine out, turbo removed job to access the starter.
Also, be sure to check all the mega fuses in the trunk, I understand that the "clunk" is in the trunk, but what about the "Grunt" you mentioned from a while back, were the batteries low then also, how long did the vehicle sit, did you have a battery tender on either battery at all ?
Thank You for the reply. Sorry if my Grunts and Clunks are not clear lol.. I only had one "grunt" from the front which I suspect was from having barley enough juice to turn the motor a bit but not start. I have since removed the large battery and put on battery tender. Its been charging for about 24 hours and went from 3V to 11.8 after 24 hours... I checked the small starter battery (still in the car) and it reads about 10.6V.. I am thinking of charging that as well.. I think it needs to be around 12V+ as well? I checked all the fuses in the trunk and under the steering column and they all look good.. so I am hoping after some good charging I can get this best fired up.
You need more than a Battery Tender to put a full charge on the battery. Use a 10 amp or better charger. Harbor Freight has one that's on sale for $35 that I use and like. https://go.harborfreight.com/coupons...0581-60234928/
However, that being said, I recently had to bring it to the shop for an overnight charge/conditioning to bring back the house battery.
Thank You Bruce.. My Father has a 10amp that I am going to try. Cheers!
I also ran a quick Ross Tech Scan as well.. The Acc Auth error at the top also makes me think my Fob may be bad,. I did swap the batt on that as welll..
I think all those communication errors may be due to the low voltage on the house battery. How old is the battery? Here is Florida we're lucky to get 3 years out of one.
Great question. I am not too sure. This car came from Dubai. My buddy is a car dealer and does high end stuff.. Mclarens etc... I have a large driveway so I've become a sort of storage spot for him.. lol.. I pulled the batteries tonight and got a nice 75A charger my father lent me... I put some pics below of the starter and main battery. Not sure if any markings on here will tell the date. The starter battery says fully charged and I metered it at 14.6V with nothing attached so I think it's fine.. the large battery is metering at 12.4V and looks like it needs some juice.. the new charger I attached is showing 65% charged.. a new battery may be the fix.. I drive an RS5 myself.. but I assume a new large battery will run a few hundred bucks? is that about right? will try that next..
I also agree with your comments about the errors.. computers are probably throwing wierd codes due to low power.. thanks for your help.. will let you know how the charge goes
That sticker to the left of the positive terminal on the big one shows a date of Feb 19, 2017 so don't be surprised if it needs replacement. Dubai is even hotter than Florida! About $200 for the new battery in the US. Costco has good prices. That's an H8 size... same as I use in my Jag XK8. The 35 over 16 stamped on the negative terminal of the smaller battery may indicate week 35 of 2016. That one is an H5 and runs about $170. Or you could go to Bentley and pay at least double. Since the smaller battery is only used for starting they typically last a little longer. Hope the high amp charge gets you going.
Thank You! I like the Costco option.. Will give the charge a try, but based on your 3 year usage comment, I'm probably just buying some time on something that should be replaced.. Got the big battery on the charger will see how it goes.. Have a great night!
I now have lots of charge in both batteries, but still no-go.. everything lights up.. remote trunk, console, lights, all looks good.. but can't fire the starter..
I may have re-connected the batteries in the wrong order.. I read somewhere that I may have tripped some battery module or something which may have disabled the ability to start the car. Does that make sense? Is the rats nest of cables needed to start the car? it seems almost like a blown fuse to the starter or something as everything is bright and ready to go.. but the key does nothing.. parallel or starter battery only.. I was also thinking maybe one of the terminal cable in the engine bay could be used to start.. I used a small 12V pack to get the trunk open when I first tried to get the car going.. maybe the other terminal in the engine bay could be used to boost? I did find the little cable on the passenger side that allows me to move the gear leaver to neutral.. I might just do that and tow it.. lol. good thing this is just a science project and not my daily driver.. cheers.
08-04-2020, 05:27 PM
.. At least the key works on this door with a dead battery. I was able to open the hood and use a little power pack on the terminals in the engine bay bay to get enough power to open the trunk.. Part 1 - success. I see the two batteries.. (Small for starter, large for other electrical).. I put a meter on the small batt and it's giving off 12.3V (around).. the large battery is pretty much dead.. (2-3V).. I put a booster on the large battery and waited a bit and jumped in the car. I get the onscreen display.. lights work.. everything is bright and looks good.. I turn the key (right).. and nothing... I try the left then right trick to switch batteries.. nothing.. I checked the connectors on the small battery and everything looks fine.. I even borrowed a brand new (large) battery and still nothing... I then used my own car with cables as the source and did get the "Clunk" sound on the emergency key turn which tells me there is power and the battery is switching.. but nothing from the engine.. I recall a while back getting a slight "grunt" from the starter but this was a while back.. I checked the fuses in the back battery area.. and around the steering column which all look fine.. Short of towing this car away.. does anyone have another idea or trick I can try to get this beast running? 
