Won't start, new battery, plenty of voltage...

[levdeb]

So our 2006 Cayenne S doesn't like to start. The battery is 100% charged. Hop in, turn the key, and it just clicks, lights all go out, and then locks the key in the ignition. Hook up the voltmeter, and there is at least 15v... Hook up the battery pack to jump start, and it fires right up... every time.

I've (in the past) tried using a battery cut off switch, replaced the cables, replaced the battery, and more. Now I am starting to hear about where the cable goes thru the firewall to the starter being a potential problem. I can't find any diagram to show where this is. I'd like to do some sort of continuity check from the inside to the engine bay.

Again, plenty of power on the engine side of the firewall. Seems like the power is being lost from the key to the starter.

Please help. Thanks!!

Oh, and only the one battery, none in the trunk.

[honerboys]

is the battery under the seat on 06's - might be bad connection at battery terminals - if they are dirty you could still see enough volts but it can't push enough amps through to spin starter - where are you measuring the voltage - jumping posts? - check for corrosion there also

[levdeb]

Originally Posted by honerboys

is the battery under the seat on 06's - might be bad connection at battery terminals - if they are dirty you could still see enough volts but it can't push enough amps through to spin starter - where are you measuring the voltage - jumping posts? - check for corrosion there also

Morning! So its under the seat. I have new battery, new cables, and did the splices in the footwell. HOWEVER, something new today...

I had the Cayenne on a charger all night (at the posts in the engine bay). This morning I went to the garage and there was a CLICK sound. It was the 404 relay in the engine bay fuse box for the fuel pump.

ALSO, when I tested the voltage (at the posts in engine bay), it was only 2.5v. And so I tested it at the battery itself, and it was also 2.5. I took the battery out and put it on my bench, and tested it one more time, and it was around 10v...!?! I've had the charger on it for maybe 2 hours and its 100% charged.

I just found where the positive cable runs from battery to engine bay and its all clean and tight with good continuity.

So, even more confused today...!

Thanks for the insight though. Appreciate any extra set of eyes on this problem.

p.s. I do have durametric setup, but its not shown anything out of the ordinary...

[honerboys]

so you had it on charger all night.. charging it from the jumping posts in engine compartment and it only had 2.5 volts but when you charged it on bench it was fully charged in 2 hours?? - might there be a problem at the jumping posts - will battery start car now? - i don't know what the clicking fuel pump relay means - but cars do weird things when battery voltage gets too low

[levdeb]

Nah, it still doesn't start the car every time. However, if I leave the battery disconnected, and ONLY use the engine post to jump it, it fires up every time....?! Very frustrating!

[honerboys]

according to diagrams the battery cable runs to the jump post then another cable runs from the jump post to the starter - can you start the car with your bench charged battery connected to jump post? - if so i'd say your problem is between the battery and jump post - you mentioned splicing wires somewhere - are the spices good? - also between battery and jump post there appears to be a large fuse - says it's down above the battery - also something called a battery sensor ..not sure what that does or if it must be reset after dead battery? - here's what i got

[levdeb]

Originally Posted by honerboys

according to diagrams the battery cable runs to the jump post then another cable runs from the jump post to the starter - can you start the car with your bench charged battery connected to jump post? - if so i'd say your problem is between the battery and jump post - you mentioned splicing wires somewhere - are the spices good? - also between battery and jump post there appears to be a large fuse - says it's down above the battery - also something called a battery sensor ..not sure what that does or if it must be reset after dead battery? - here's what i got

The splices are those common ones in the footwells that get wet, so we started there.

The battery is new, but when its plugged in (ground cable connected) it won't start. If I unhook that cable, and use the posts in the engine, it fires right up. I will use your schematic and dig a bit deeper. Thanks so much!!