Jump starts and ECU

[M]

I just popped in to my local parts shop to pick up some new jump leads to start another car. When I told the bloke what car I had he warned me I could damage my ECU with a spike. I googled it and also found the following info. Does anyone know the reak score on this?

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"I vaguely remember something about putting your sidelights on when jump starting. Something to do with regulating the power so it doesn't spike the ECU !"

ANSWER-
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"Sounds like an old wives tale to me. The car already has a voltage stabiliser else the spikes would destroy the radio, sat nav etc etc.

What you mustn't do, which most people forget, is to jump start the other car with your engine running.

Connect the leads, leave your engine running for a few minutes at slightly increased revs to charge the recipient, then switch off you ignition then try to start the other car. If you turn the key in the flat battery car while the engine in the donor is running (and charging the battery) the dead car will attempt to draw all the starting current from the battery and alternator of the working vehicle. This can cause the alternator and charging circuit to burn out. There is no point leaving the engine running (and the charging circuit open) whilst attempting a start as the alternator can only supply a handful of amperes whereas the battery can supply hundreds (for a short duty cycle).

Trying to start the dead car using your own cars alternator is an easy way to burn it out."

 

[patrick]

well, I have looked all over the web, but was unable to find a gude that actually said you should try to start a dead battry with your own car turned off, but site said something along these lines............

Jump-starting: The best way to start your car if the battery is flat is with Jumper cables. These are heavy duty cables which carry the current being produced from a healthy car to your battery so that it can start your car. Connect the jumper cables one at a time being careful not to touch any metal parts of your car (or the other lead). Connect positive to positive and negative to negative. The healthy car should then rev the engine and allow about 10 seconds before your first attempt. Usually you should be able to start the engine within a short time but if the turning of the engine seems slow then wait longer before tries. As you try to turn the engine over the healthy car should be revving the engine (Not excessively, just around 2000-3000 rpm). I there is nobody to help or no-one has jump leads then you can phone a Taxi and request for one with jump leads.

Bump starting: This can only be done with manual transmission and not an automatic.
Step 1. Get a few healthy lads to give you a push.
Step 2. Turn on the cars ignition and put the car into second gear.
Step 3. Make sure your handbrake is off and remove your foot off the foot brake.
Step 4. Making sure that your foot is on the clutch ask you helpers to start pushing.
Step 5. As the car reaches the fastest speed that you expect it to reach quickly lift your clutch pedal and press the accelerator slightly.
Step 6. If the car does not start then repeat these steps until exhausted. Then call a mechanic.

 

[Tom]

Gawd, there is so much utter bullshit out there.. how on earth is jump starting going to 'spike' something?!?

Its not like you are wiring the car to the mains or anything!

You shouldn't push start a car with a catalyst. That CAN damage them.

 

[M]

OK Tom, have patience. I am an ignoramus where cars are concerned. I know about other stuff, but that's irrelevant

This guy in the parts shop lost a sale through his advice, which is why I was more inclined to listen. I'm ignorant enough about cars to be worried by such comments

To clarify: It is perfectly safe to jump another car from the Bravo?
Leads - should one end of the earth lead be on the chassis (something else he said) or both ends on the neg of the batteries?
Should the Bravo be running or off when jumping the other motor?

Ta

 

[Tom]

Its perfectly safe and that guy is a ****wit.

Its always been the rule with jump starting, start the good car, connect the leads directly to the good cars battery and then connect the pos to the dead batt and the neg to the dead cars chassis. Give the good car about 2000rpm and away you go.

As for spikes its no worse than when you start your own car.

 

[M]

Thanks