Jump start procedures

In news:crtl6q$d5p$ snipped-for-privacy@ucsnew1.ncl.ac.uk, Mark Hewitt decided to enlighten our sheltered souls with a rant as follows

Keep your electric load low, rev to around 2500 rpm - once the leads are connected, obviously.

Once the Cav is running, before you disconnect the leads, turn the heated rear window and the heater on in the Fiesta. Full blast on the fan, but don't use the headlamps [1]. Then disconnect the leads.

[1] The surge when the leads are disconnected can blow bulbs.

| In news:crtl6q$d5p$ snipped-for-privacy@ucsnew1.ncl.ac.uk, | Mark Hewitt decided to | enlighten our sheltered souls with a rant as follows | > Just heard my Dad has broken down again and needs a jump start to get | > his car going, I'll be along later in the day for that... | >

| > My question is how best to provide a car with enough power to be able | > to start, using jump leads.. My car is a petrol '04 Reg Fiesta and | > his is a petrol H Reg Cavileer if that makes any difference. | >

| > Last time we did this he got me to rev the engine hard as he said | > that will put more power through the jump leads, is that the case? | >

| > Also should I keep my own electric load, such as headlights, low or | > high? | > Many thanks for any tips! | | Keep your electric load low, rev to around 2500 rpm - once the leads are | connected, obviously.

Yup!

| Once the Cav is running, before you disconnect the leads, turn the heated | rear window and the heater on in the Fiesta. Full blast on the fan, but | don't use the headlamps [1]. Then disconnect the leads. | | [1] The surge when the leads are disconnected can blow bulbs.

Surely at this stage both batteries will have some charge and will effectively limit any voltage surge.

I have jump started *many* cars without trouble.

I just disconnect the jump leads taking *care* not to touch either car or the other jump lead.

In news: snipped-for-privacy@4ax.com, Dave Fawthrop decided to enlighten our sheltered souls with a rant as follows

Unless the battery on the car that's being jump started is utterly knackered. That's when you get the surge.

That normally does the trick just fine. Have you ever noticed that your headlamp bulbs seem to blow shortly after jump starting a car at night though?

Not every time, but it does happen, hence most car handbooks telling you to put the heater on, etc.

The message from "Mark Hewitt" contains these words:

No. Just a fast idle will be plenty. What really helps is being patient

- take five minutes instead of two and it'll start no trouble. Oh, and don't use cheap jumpleads about as thick as a bootlace - they're useless.

Remove the earth lead off his battery and connect your lead up to that as it means you're powering the car electronics and not charging his battery whilst you jump start the car. Once its running re-attach it to the battery.

If you remove the earth lead off the flat batteried car, you don't need to wait at all.

Just got back.. didn't work :-(. Put a gallon of fuel in it and spent about

15 minutes trying to start it. The starter motor worked fine but the engine wouldn't fire, not even spluttering. Going to have it towed home so we can have a proper look in the daylight (it's about 2 miles away at the moment)

make sure you CAN jump start the car first many modern cars blow important bits of electrics if you try to jump them without turning other stuff off (BMW's in particular) although, you say you have an 04 fiesta, it's got PATS and even if you've blown a bulb on the dash they won't start as everything electrical is integrated if you've tried and failed to turn it over then check the fuel cut off switch many a times been wasted in the garage because the person has forgotten to press the button

The message from " dojj" contains these words:

How certain is this? I've heard apocryphal stories, and I'm sure the manuals tell you not to in order to cover themselves against lousy design, but I've not actually met anyone who's shagged something that's definitely attributable to jumping a car.

Not sure how you can get a surge, unless the slave car's battery is well and truly knackered. A good, but discharged, battery will have an internal resistance so low as to prevent any surge. And you'd need some surge to blow a tungsten lamp. Anything electronic - like the radio - is far more likely to suffer.

This is something I'd not risk. With the car started, but no connection to the battery, if the donor battery connection is broken while trying to make the earth to the slave car, the volts from the alternator can go sky high.

Connect both batteries with the donor car engine stopped. Start donor car, and run it at a fast idle for about 5-10 minutes. This will charge the flat battery quite a bit. It will be necessary if your jump leads are thin anyway. Then start the car, and disconnect at the slave car first.

IME you need a very good connection on the clips to start anything other than the smallest of petrols using that trick. You also have the problem of reconnecting the battery - it can end up doing the arc welding trick.

It can also arc as you connect up and end up spatting molten lead from the terminal post everywhere. I wouldn't recommend it.

I usually connect the leads with the donor cars engine stopped- a healthy donor battery should be perfectly capable of firing up a warm donor engine even with the load from the flat battery.

Connect the leads making sure of a good connection.Connect the neg at the flat battery end to the chassis or engine block. NOT the battery.

Then start the donor and rev to just over tickover- 2000rpm is plenty- the alternator will be spinning plenty fast enough to generate full output.

Start other car and apply full fan / heated window etc. Allow it to idle then remove leads neg first.

Tim..

Which is why the recommendation is to connect the positives then one negative and the final negative (assuming negative earth) to the dead vehicle on an earth below the battery top. The theory being if the donor vehicle is gassing and the dead battery similar then hydrogen is present an rising from the cells.

AJH

Dead batteries don't gas. It's a condition of a fully charged one. Hence make the final connection and disconnection to the flat battery. But in any case, pretty well all cars being jump started will be outdoors with the bonnets up. Hydrogen rises very fast, and would disperse. The problem used to arise in battery charging rooms in garages, where there was no vetillation.

You are correct Dave, except there is the possibility something else may have happened, so we are taught to make the final negative connection to the donor vehicle and to a point below and away from the battery.

Gassing will occur when the battery is incapable of accepting more charge. So the scenario of a faulty starter connection leading someone to think their battery is flat, charging it and still finding it won't turn over is a possibility. It's a small point and not one that is vital in most cases.

I have a guilty memory from 35 years ago of trying to jump start a MF35 4cyl perkins with 2 6V batteries, using a 55A dc supply from a welding transformer :-(. One of the cells jumped out of its retaining pitch. In this instance the gassing had occurred from the cell being shorted internally and previous enthusiastic attempts.

AJH

Maybe I've always benefitted from fitting beefy batteries, but I won't actually *start the engine* of the donor car unless I absolutely have to.

Which isn't very often! The recipient vehicle (even a 2.9 Scorpio Cosworth, totally flat battery) has always started OK without my needing to start the engine of mine.

For info, I drive a Ford Mondeo 2.0 with a beefy OEM ford Calcium battery. Saves any risk of alternator damage etc. to my car.

Regards

Alan