Jump leads - beware !

Silvera

The 'what emergency kit' thread reminded me of this -

If you own a modern car (i.e. if it has an ECU etc) do not use standard jump leads when you have to jump start the car ....... or another car.

Why?
because standard jump leads could cause an electrical 'spike' when jump starting, which could damage your ECU.

- Either buy new leads with the safety device attached,
- buy the safety device and fit it to your existing leads, or
- buy the jump lead that goes from the cigar lighter in your car to cigar lighter in the other car
I don't know how effective this type of lead is as the cable is very light. May be ok if your battery is not too run down.

Just a 'heads up' for you guys.

Silvera.

(P.S.- I didn't damage any ECU, I just read that this can happen with standard leads)

Capt'n Midnight

How about the Beamers with the battery in the boot and fitted with explosive bolts to disconnect it in the event of a crash ?

Is the safety device anything more than a ferrite ring ?
If so then could whip one out of a dead computer psu

Heathen

thanks for that Silvera never really thought about that

lomb

where do u buy safety device silvera? must get one.

Silvera

I haven't bought one yet either.

I saw one advertised in a UK mag for £17. I presume any good motor factors here should stock them.

The safety device basically has c.six 'pins' enclosed in a plastic case which clips over your leads, and the 'pins' push into each lead.
Actually,it may be easier/quicker to buy new leads.

lomb

probably right. 17 £ is nearly 30 euro......

Capt'n Midnight

Do both leads fit in the one case ?

Silvera

yes, but they are seperated by a plastic section.

mike65

My car has an Overload Protection Relay connected to the ECU I presume its
to protect against voltage spikes and such like.

Mike.

Seth Brundle

Capt'n Midnight wrote:

How about the Beamers with the battery in the boot and fitted with explosive bolts to disconnect it in the event of a crash ?

My owners manual states that one of these types be used rather than normal ones. Given the cost of a new ECU I think Id rather fork out for the leads!

trotter_inc

mike65 wrote:

My car has an Overload Protection Relay connected to the ECU I presume its
to protect against voltage spikes and such like.

Mike.

I made an ECU for my final year project in college - most modern ECU's have this relay which is exactly for the reason you mentioned.

fletch

I also remember reading somewhere that you shouldn't push start modern cars anymore because doing so can force un burnt petrol into the cat converter & wreck it which of course can cost circa €1000 to replace

lomb

yeah but saying that a drove a cated car for 3 weeks on 3 cylinders with loads of unburnt fuel coming out of it and did the nct the other day and it passed with a very wide margin on the CO emmissions so that tells me u dont need a cat to pass. (98 car )

DukeDredd

Don't BMW's have connections in the engine compartment for connecting jumpleads so as not to jump directly through the battery?

Seth Brundle

some BMWs have two connections in the engine bay - but I think both are earth points

mike65

trotter_inc wrote:

I made an ECU for my final year project in college - most modern ECU's have this relay which is exactly for the reason you mentioned.

I'm impressed!

Mike.

mackerski

kbannon wrote:

some BMWs have two connections in the engine bay - but I think both are earth points

My E46 has a battery in the boot and a positive terminal (with cover) in the engine compartment for jump-starting. (for the ground, you pick your own). I can't recall the manual expressing a preference for clever jump leads.

Dermot

hefty_langer

Corredct me if I'm wrong (and probably am...)
but I read somewhere that if you are going to jump start a car you should have the headlights turned on to protect from any voltage spike...
..Would this protect your ECU? or just an old wives tale?

Villain

Is it true if you jump start some Renaults, it could cause the airbag to go off??

Probably a myth

mackerski

irish1 wrote:

Is it true if you jump start some Renaults, it could cause the airbag to go off??

It might if you try to start it in first and it's nosed in alongside a wall.

Dermot

Villain

mackerski wrote:

It might if you try to start it in first and it's nosed in alongside a wall.

Dermot

lol very good I like it

trotter_inc

mike65 wrote:

I'm impressed!

Mike.

It was only for an Astra - '98 I think. Did it down there in WIT in Waterford, they have sh*t loads of engines mounted on wheels that the mechanics in FAS use which is great!

Seth Brundle

mackerski wrote:

My E46 has a battery in the boot and a positive terminal (with cover) in the engine compartment for jump-starting. (for the ground, you pick your own). I can't recall the manual expressing a preference for clever jump leads.

Dermot

<Geek mode>
My (1997 E39 523i) manual states:-
"Use only cables with fully insulated battery post clips, e.g. to German DIN 72551 standard or equivalent"

It also mentions:-
there is a + terminal on the engine which if your car is being started will connect to the + of the donors battery.
There is also a nut on one of the strut housings to connect the - terminal of your car to the - terminal of the donor battery (or a suitable ground on the donor vehicle) .

mackerski

kbannon wrote:

<Geek mode>
My (1997 E39 523i) manual states:-
"Use only cables with fully insulated battery post clips, e.g. to German DIN 72551 standard or equivalent"

Yup - that's about the minimum cleverness you can get away with in a jump lead.

Dermot

Seth Brundle

so I see!

DukeDredd

Bloody hell - i don't know why so many people still think BMW's are the best - look how fricking complicated it is to jump start one. And the fact you have to jump start it in the first place should be telling you something.

mackerski

DukeDredd wrote:

Bloody hell - i don't know why so many people still think BMW's are the best - look how fricking complicated it is to jump start one. And the fact you have to jump start it in the first place should be telling you something.

It's about as complicated as for most cars, no? Apart from having to think about where the positive terminal is.

Dermot

knifey_spoonie

What you shold do is turn the key to acc.then on to let tho power trickle trough, if a car is completly flat and it has airbags a surg of power can set the airbags off so its best to leave the ignition on the on posistion for about 30 secs.

If you do this you wont kill your ECU

P.S. above advice given to be taken at the users risk.

Tenshot

hefty_langer wrote:

I read somewhere that if you are going to jump start a car you should have the headlights turned on to protect from any voltage spike...

I don't know about protecting from voltage spikes (maybe it does) but I always have the lights on anyway so that I can tell when the jump leads have got a good strong connection -- the lights get much brighter.

Father Hackett

Last threads all make sense but... in a FIAT owners manual from some year's ago; it advised to turn off all items (including headlights) as 1) switched on halogen light may get blown by a voltage spike [>14v] 2) Puts increased strain on both cars electrical systems involved when it may need all current/voltage available.
And FIAT should know; more lightl to end up jump starting at some point!!

As an aside; ECU blew on my FIAT due to dodgy battery connector (Battery itself was fine)... so some ECU's at least can't cope with Voltage drops/peaks.. 360 odd quid (old money).. so wanna be very careful installing/removing battery connections