Hi all,

I needed to take my XK to the MOT and won't start... I tried charging the battery but alas I think it needs a new one.
Anyways, I want to jump start it to drive it to the garage (I have a mini I can use for that). However, when reading the manual, it says if you jump start it (boost start), the other vehicle's engine should not be on.... I am a bit puzzled as I thought this risks draining the other vehicle's battery... 🤔 Any views?

(Even though I had on my to do list to buy a trickle charger, I let the battery drain a few times and I think it won't charge properly anymore now...)




Thanks

 

When jump starting from another vehicle it is always the case that you should have the donor vehicles engine off.
otherwise once the car has started you could have two charging CCTs working against each other which is not a good idea.

 

I have always boosted a car from a running vehicle never an issue, did the same to my jag a couple years ago.

 

In the ‘old’ days it was normal to jump from a running car, but with all the electronics in modern cars, there’s too much chance of frying something.

 

Ok, better play it safe. But will it not drain the other car's battery?

 

It will take some charge out of the donor car's battery but it should start well before the donor car's battery is drained. However, you will need good thick high-current cables with strong clamps as the V8 draws a high current. Once the Jag has started you can recharge the donor car battery or take it for a long run.

If the Jag engine turns over too slowly to start or the jump cables start to heat up, your cables are not up to the job. If you have a second set of cables you can use them doubled-up to enable more current to be passed.

Richard

 

I usually try it first without the donor car engine running and that usually does the trick. However, if it doesn't start but sound close to firing, I start the donor car to generate a bit more ooomph, I've never had a problem with either method but having good cables and clamps is essential for large capacity, high-compression engines.

Richard

 

load dump damage

use a jump pack

 

While I've yet to come across the actual bulletin, this older article notes Jaguar recommends against it siting damage the the engine harness.

fwiw

https://chiptuning.com.au/2015/06/23...ing-procedure/

 

If it does then you need a new battery in the donor vehicle too.

There's a lot of sensitive electronics in the Jaguar and a 'spike' could do expensive damage. Probably won't but why take the risk?

Graham

 

Ha yes didn't think about that... :-( My cables are probably not up to the job for such a large engine (they are not tiny but probably designed for like a 2.0L engine... Can't find any markings on them.)

 

easy way to have two cars with dead batterys if you ask me. If dead car dosent start from boost it might have sucked enough juice out of donor car so that it won't start. I will go with what has worked a 100 times for me.

 

my wife bought one of those small Portable Power Bank Jump Starter things for each of our cars. i was a little annoyed until of course I needed to use it in my Acura several times and my daughter used hers to. small and buys some peace of mind. have not needed for the jaguar yet but i am sure one day i will

 

Yep. I bought one of those battery packs, and have used it (3 - 4) times on a partially run-down battery. Much recommended, and gives peace-of-mind.