Vauxhall Cavalier (1988 - 1995) - 95 2.0 Jump starting car -why -VE connections this

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Wed 6 Aug 2008 22:07
95 2.0 Jump starting car -why -VE connections this - peter973
When jump starting a car from a booster battery why do they say you should connect the -VE of booster battery to car engine block/bolt (away from battery) & NOT to the -VE of the car battery ??

Yesterday my battery was flat, tried connecting -VE of booster to engine block, would not start, probably not good enough connection.
Connected -VE of booster to -VE of car battery, started ok.

I've never had a problem connecting the -VE and +VE of booster & car batteries to each other.

{added model of car, picked up from a previous posting so people will know the car you're asking about}

Edited by Dynamic Dave on 07/08/2008 at 01:17

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Wed 6 Aug 2008 22:28
95 2.0 Jump starting car -why -VE connections this - topbloke
the reason for connecting the neg terminal to the engine is mainly due to not wanting a spark anywhere near a battery that may have been gassing and subsequent claims for damage or worse, However the poor/non starting when the neg clamp was put on the block may be the cause of the flat battery not unuasal for the earth leads to corrode on these vehicles
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Wed 6 Aug 2008 23:07
95 2.0 Jump starting car -why -VE connections this - defender
I was also taught that as well as the possibility of battery gas going bang that a flat battery will soak up some of the power from the jump leads that you are trying to start the car with and that connecting negattive lead away from battery prevents this
however with many newer cars with modern electrics it is often safer to put both leads on to the battery and run donor for 5 or ten minutes to boost battery then remove leads before starting as there is less chance of damage although you can get jump leads with an anti spike device fitted which prevents damage

Edited by defender on 06/08/2008 at 23:08

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Wed 6 Aug 2008 23:18
95 2.0 Jump starting car -why -VE connections this - peter973
I've searched for old threads & there seem to be many different views on the way to jump start a car & the reasons why !!

Jump starting: conflicting advice
www.honestjohn.co.uk/forum/post/index.htm?t=38895

Jump starting
www.honestjohn.co.uk/forum/post/index.htm?t=24318

flat battery and jump starting
www.honestjohn.co.uk/forum/post/index.htm?t=12728

Jump starting
www.honestjohn.co.uk/forum/post/index.htm?t=4623

I wouldn't mind if I could find a decent connection point for the -VE on my engine block.
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