jump start positive earth from negative earth

[beertownmorris]

hi, sorry if this is a stupid question, but if you don't know the answer......
I recently acquired a morris and have had little time to use it since
Now I cannot start it. It started ok 3 months ago.
Engine turns over fine for a few turns, then the battery runs flat
I have charged the battery, but same thing happens
I could get a new battery, but wanted to check that this is the fault.
Question is, can I try to jump-start the morris, which has a positive earth, from a car with negative earth?
If so, do I still connect positive to positive, negative to negative?

Thanks
Andy

[PSL184]

NO !!!!
If the battery is going flat after turning the engine a couple of times then it is dead and needs replacement. Check the voltage with a meter. Anything less than 12.5 volts will not start the car.

[bmcecosse]

YES! Of course you can jump start it - and yes you must make sure it is connected +ve to +ve and -ve to -ve - just make sure the two cars are not touching each other. So the earth on the donor car will connect to the battery -ve on the Minor, and the earth on the Minor will connect to the +ve terminal on the donor. Run the donor engine for 5 minutes at fast idle before attempting to start the Minor. It could be you DO need a new battery - but may as well start it on the jump and see what happens after that.

[PSL184]

and risk blowing the ecu if you are using a modern to jump start.... at your own risk and not recommended by me at all.

[bmcecosse]

Why on earth would it blow the ecu ??????? Is this something from personal experience ? Connect the leads and THEN start the modern and let it run at fast idle for 5 minutes.

[MarkyB]

Modern cars are delicate beasts!
http://www.google.co.uk/search?q=jump+s ... u&ie=UTF-8

If you disconnect one side of the battery from the modern car it should be OK, as long as the owner knows the radio code.

[kennatt]

yes but they mostly talk about jumping a modern off causing a spike in the ecu,we are taking the other way round ecu car to another battery done it loads of time never even considered that it was a problem can't see why it should be.Once the modern is running(So long as pos to pos and neg to neg) all you are doing is asking the alternator to charge until both batteries are full(If left long enough)can see no reason to be wary about it.

[beero]

Welcome to the Forum Andy.
Is it not possible to take the battery off the other car and fit it to the Minor?
As has been mentioned, make sure you have the radio code!

[PSL184]

Is this something from personal experience ?

Not on my own car but a friends Punto was scrapped because the required ECU would have cost more than the car was worth....

[bmcecosse]

He must have done something very silly.......and the car must have been ropey or surely another ecu could have been obtained from a scrappy ??

[IslipMinor]

Connect the leads and THEN start the modern and let it run at fast idle for 5 minutes

As Roy as already said, this is the way to do it, and I cannot see that one car being +ve earth and the other being -ve has anything to do with it. I have jump started a number cars with my 'modern' and used the above process, always remembering +ve to +ve and -ve to -ve on the batteries first, then start the donor car, run it for a few minutes at fast idle, then start the receiving car. Works every time for me with one proviso - the jump leads must have good connections both ends of the leads! But that is another story.