Quick Question - Jump starting

[garycox]

Sorry if I'm being thick here...My friend has a flat battery in his car (Fiesta, petrol) and I offered my van (Transit, diesel) to jump start it.He was advised that this is a bad idea, is this true and if so why? I've used it on my own cars in the past.Cheers

[Mr_Bo11ox]

dont see any problem at all!

[pogweasel]

If you were going t'other way round it would be more 'difficult'.Look at the jump leads you are using. Are they cheap & cheerful ones off the market for a fiver, or are they the jumbo thickness cable, fully insulated jobbies. It makes a difference. Tried to start a Land Rover (enormous battery) off my old BMW (small battery)... result = melted cables. After that I went out and got some super jobs with a really thick core, basically suitable for jumpstarting HGV's/tractors/plant etc and have OBV had nay bother since. A bonus is the priceier ones have much longer leads so you're not pissing about getting the 2 cars 0.03mm between each other.

[Mr_Bo11ox]

Thats not the fault of using a big battery though, its the fault of using flimsy cables.

[kelvin2008]

jump starting modern ECU controlled cars has been known to damage them, I personally know of a BMW petrol 3 series that the AA killed by jump starting and a Rover L series diesel which would only run with the ECU body earthed after a jump. No worries with carbs n dizzies though

[pogweasel]

What? How ridiculous is that. Why are they now designing stuff you can't get running again by simple, logical means? Idiots.That said, how complex is a diesel rover, ECU-wise?

[Richard]

It's always been good practice to leave the leads attached for a few minutes once the dead car has started. If you remove the leads too soon you put a sudden 100% demand on the alternator, which can damage the voltage regulator circuit- and on newer cars it can damage the ECU.

[kelvin2008]

yes its kinda put a stop to me being helpful anymore by offering jumps unless its proper old shite, but I still always carry my meaty set of jump leads ive had for years in the boot. Old habbits die hard.Actually that rover L series diesel engine is quite a complicated system, got a cat, turbo boost control, intercooler, EGR the lot, long production run to from 1996 till death of rover and was fitted in the MG hot versions of the 220 and 420. Firmly in shite territory now too.

[Milford Cubicle]

Does it? My ECU-controlled Ford Scorpio TDi got a jump off an even more complicated Fiat Multipla JTD recently.

I've never heard of the L-series problem either, my Rover 220Di got a jump start or two because of its crappy battery, but it never caused any problems.

Have you been putting the earth lead on the ECU or something?

[kelvin2008]

http://www.bba-reman.com/content.aspx?c ... diesel_ecu

[Milford Cubicle]

Hmm, didn't kill mine. I imagine they're more liable to dying due to their crap location.

[kelvin2008]

its the "one way valve for electricity "power transistor between the ECU mainboard and the outer casing that blows hence if you earth the casing it still runs, the ECU is also linked to the immobiliser so just plugging in another one from scrappie doesnt work

[andrew e]

Jumped a stone age 98 E39 (runs a nikki carb ) with a 05 Rover 25 facelift (had electronic brakeforce and rusty hinges ) No problems. Not sure why it went flat mind.

[andrew e]

Twin choke Nikki you know, I'ts on last remaing payments from the 1987 Kays catalogue.