Jump starting

[TJB]

Hi folks,
Is there any special precautions that need to be taken when jump starting something off the TJ...? I've heard fifth hand rumours the on-board computer(s?) don't like it too much...

[LEXX]

Just need to make sure that the jump leads you are using have a surge protector inbuilt, don't use straight jumper leads as your comp will hate you.

[Saxon]

I have jump started off my tj many times with no probs....However maybe thats why my engine warning light is on all the time :?:

[wrench]

Hey guys
Most mechanics including myself happily jumpstart EFI vehicles, & from EFI cars with ordinary jumper leads. However this requires a degree of caution & discipline to follow the correct procedure every time. When done correctly there is no risk to either car however it does take time.
If you arent sure or can't trust your helpers then buy a quality set of surge protected leads.
David

[Wooders]

I've used mine many times - I'm always careful....but I always wonder if I'm about to fry the electrics :oops:

[MattW]

You can buy a spike protector which you just wire to both terminals on your battery. About $30 i think. Then you can use any leads without worry. Or less worry as i still do :mrgreen:

[Laz]

From a Electrical perspective, a surge surpressor is a large capacitor (with inbuilt bleed resistor for saftey), as such this add's "Electrical Interia" to the jumper lead circut, hopefully arresting any "Spikes".

I am however at a complete friggin loss as to how some puny arse surge arrestor is going to add ANY protection WHATSOEVER againt the monster capacitative value of the car's battery?????? IT IS ENORMOUS!!! (like at least a 100 times larger than any surge surpressor......)

The primary issue for onbaord computers is relative path to ground when attaching jumper leads - you bsically don't want the computer trying to supply current to the starter motor (ehh gad) - to protect yourself make sure that the battery is properly grounded to both the chassis and the engine block, make sure you have good quality termal connectors and if you get the chance - solder the ends on the leads - this will stop corrosion.

ooooh time to hop off my nerdy soap box Penguin

BTW - I have a couple of sets of Snap-on 500 amp jumper leads that have meaty copper connectors - these are brilliant and at 4 meters long are sure handy.....

[wrench]

Laz
The battery itself is not a concern unless unless someone connects the leads wrong creating a 24V circuit (BIG SPARKS). Of more concern is the alternator surge if the motor is revved after starting & a helper rips the jumper leads off, usually just as the alternator starts to replace the depleted battery charge. Surge protected leads wont help here but an on board protector may.
David.

[Jaffas]

However this requires a degree of caution & discipline to follow the correct procedure every time

And the correct procedure would be?? :?

[LEXX]

YER LAZ, come on!!!!! Please tell us mear peaseants what the right procedure is?

[Wooders]

Jaffas,

I have NFI if this IS the correct proceedure but my personal method is:

1. Start Jeep,
2. Connect one end of black lead to Jeep neg battery terminal & other end to dead japcrap neg battery terminal,
3. Connect one end of red lead to Jeep pos battery terminal & other end to dead japcrap pos battery terminal,
4. Let idle for a minute or 2.
5. Start japcrap. Leave jeep idling.
6. Once started remove japcrap pos end, then Jeep pos end,
7. Remove japcrap neg end then jeep neg end.
8. Shutdown jeep.
9. Roll leads up & store for next broken down japcrap.
10. Laugh as idiot in japcrap stalls and comes begging for help again.......

Ok seriously if it were my car that had teh flat battery, I'd then drive up the expressway for 30minutes or so & back....if I thought the battery was ok....if I was suspect of battery I'd drive it straight to auto electrican to get the battery checked/replaced.....

Anyways that's the way I do it....ALWAYS being cautious of the lead ends to avoid arcing or a hanging cable fouling with something (eg fan :shock: )

[MattW]

I've been told its the other way around. Connect the negative cable last and disconnect it first.

[Steve F]

This is what I would do if it were my Jeep that had a flat battery.

Press little switch that will join my second battery to my starting battery by overiding RedArc isolator. While switch is held start Jeep :) Gotta love dual battery systems.

When I jump start my rarley used Beetle I do what Wooders does but I connect the positive first and I jump start from my second battery as well. I dont know if this makes any difference but I think the Isolator has some spark arrestor dodad in it.

Cheers
Steve

[Ben]

I'd ring the RACV...if they stuff up its their fault.

[Jaffas]

Yeah, fair enough, makes sense... personally I think connecting the ground (negative) terminal first makes more sense... although I have heard of people connecting chassis to chassis instead of neg to neg... but it shouldn't make a difference as the negative terminal is grounded to the chassis anyway.

Dual Battery system :D now you're talking :!:

[sir_camel]

hmmm....i had a total flat the other day. Tried jump starting but either i screwd up or the battery was totally gone. Just replaced the battery. Needed doing anyway. Was the original battery and mine is a 11/96 build date. Not a bad innings.

[mattc]

Steve F,

Firstly I am not an auto electrician....................

Press little switch that will join my second battery to my starting battery by overiding RedArc isolator. While switch is held start Jeep Gotta love dual battery systems.

I assume you have one of these RedArc models http://www.redarc.com.au/sbi-techspec.htm

I have been looking around at how to wire up my second battery to assist with winching but at the end of the day decided it is better to use it for accessories etc and as like you, as an emergency starter battery....however after surfing around the web I found a few references stating that connecting a good battery to a flat battery without the engine running is a bad idea. The batteries can quickly equalize leaving you with two half flat batteries..and still not turn over the engine. Most systems are designed for the opposite - ie the second battery is flat (ie fridge etc) and you still start on the main battery before starting to charge the secondary. A lot of controllers either limit the initial current flow or add some delay after starting.

Anway, I ended up buying a Jaycar kit (not assembled yet) which will pass 100Amps to the secondary but much less in reverse (well it will get hot because of the internal diodes in the mosfets) but certainly not pass enough current in reverse to support winching - momentary starter drain should be ok.

I am thinking of putting a 'tap' on the both batteries. That way I can isolate either from the starter. For example, if the main is flat from winching or leaving the lights on, then I can turn the tap 'off' to disconnect it from the system, start the car from the secondary, then turn the tap 'on'.

Hmmm

[Wooders]

Ok does anyone know for certain pos or neg first? (or is it makes SFA difference :?: )

[Steve F]

Mattc,

Yep that's the one I have. I agree with you on the battery equilization but if my main battery just doesn't have enough juice to turn the starter over fast enough to start I wouldn't hesitate to press the button. After all I'm already stuck with one flat battery and no go so I may as well try the second and eithier start or be stuck with two flat batteries :oops:

Should also add I've used a second battery previously (not in the Jeep) to jump start myself when I had the Jaycar dual battery kit.

Cheers
Steve

[Ando_13]

Wooders, I've always been taught to connect the Negative first, and then the Positive second. And further to this with new cars to connect the negative to the chassis ground not the negative terminal, once again first.

I belive that if you connect the negative first, then when you connect the positive the current can flow thru the natural ground of the car. This could be utter crap but I think it sounds OK.

Buy a manual and roll start.!!!

But in saying this I've jump started hundreds of times on old cars or diesels, but have not done it on a car with an ECU (or whatever the computer is called).

My 2c worth.

[MattW]

Ok does anyone know for certain pos or neg first? (or is it makes SFA difference )

Heres how i see it if you connect the negative first then when you connect the positive to the battery you can get sparks and blow up the battery. (small chance but it has happened) If you connect the positive first and then connect the negative to the chassis away from the battery there is very little chance of any spark coming anywhere near your battery.

[Wooders]

Ahh the joys of wet cell batteries huh ;)

[Bogged]

I agree with positive first. Then you have less of a chance of arcing yourself when you drop the wrench or sthing

[Laz]

YER LAZ, come on!!!!! Please tell us mear peaseants what the right procedure is?

Well this mere peasent uses the following method for Jump Starting other vehicles.
"J" = Jeep with good battery
"F" = non jeep with flat battery

1: Leave a light you can see on in the jeep - Courtesy light is fine (why? i explain in step 3) - making sure your jeep is turned off- along with the other car's ignition being off.

2: Connect Red jumper cable to the Positive (+) terminal on "J" battery first, then connect to the Positive terminal of "F" - I allways use the battery terminals (why? i explain after instructions)

3: Holding BOTH ends of the Black jumper cable, connect to the Negative (-) on the "J" battery, then while keeping a watchful eye on your courtesy light, connect the other end of the Jumper cable to the Negative terminal of "F" - when you see your courtesy light dim slightly you have made good contact.

4: Try to start "F", if it start's easily then Cool, if not goto step 5

5: Ahh so the other car wouldn't start eh? Well take the key's out of "F"'s ignition (experience has taught me the folly of leaving them in car "F")and go and start "J", let the Jeep run for at least five (5) minutes, preferably Ten. - This allows your alternator to charge to Flat battery of the other car via the jumper leads

6: Turn off "J" and hand back the keys to try and start "F" - this nearly allways works - repeat 5 if it comes close but wasn't quite enough.

Note: Removing Jumper leads
Remove negative lead from "F" first then remove from "J", then remove positive jumper cable from both vehicles (order is unimportant)

In Step 2 - I allways connect up the positives on the batteries first, starting from the jeep going to the flat car - if you are going to accidentally "arc-out" a lead then at least the body of the other car is allready connected to the negative terminal, as such the potential difference or voltage is likely to be a lot closer than with the black (negative) jumper cable than Red (positive) jumper cable.

Why not have the jeep running when the cars are connected? - well this is just good practice as most older cars (up to about 1985) have a simple regulated alternator that supplies 35-55 amps at best, with newer and certainly with much higher capacity alternator's you run the risk of "Shock" or "Surge" loading the regulator at the point of joining the flat battery into the charging circut.
Worst case is where your alternator tries to supply the starting current for the other vehicle - minimum of 200 Amps - the jeep draws around 400 Amps on start.

[Ando_13]

I hang my head in shame, positive first does sound better now :oops:

[Wooders]

Great Stuff Laz. Personally I'm MORE than happy to be corrected :!:

[blackxj]

This is the procedure from the XJ service manual:

TO JUMP START A DISABLED VEHICLE:
(1) When using another vehicle as a booster
source, turn off all accessories, place gear selector in
park or neutral, set park brake and operate engine at
1200 rpm.
(2) On disabled vehicle, place gear selector in park
or neutral and set park brake. Turn off all accessories.
(3) Connect jumper cables to booster battery. RED
clamp to positive terminal (+). BLACK clamp to neg-ative
terminal (-).
(4) On disabled vehicle, connect RED jumper cable
clamp to positive (+) terminal. Connect BLACK
jumper cable clamp to engine ground as close to the
ground cable attaching point as possible
(5) Allow battery in disabled vehicle to charge to
at least 12.4 volts (75% charge) before attempting to
start engine. If engine does not start within 15 sec-onds,
stop cranking engine and allow starter to cool
(15 min.), before cranking again.

DISCONNECT CABLE CLAMPS AS FOLLOWS:
(1) Disconnect BLACK cable clamp from engine
ground on disabled vehicle.
(2) When using a Booster vehicle, disconnect
BLACK cable clamp from battery negative terminal.
(3) Disconnect RED cable clamp from battery positive
terminal.
(4) Disconnect RED cable clamp from battery posi-tive
terminal on disabled vehicle.

[wrench]

Yeah BlackXJ's got it right & Laz the only extra is to let the flat battery charge for a while prior to attempting atarting. The idea is that the final connection is away from the battery & on the engine block so that if a spark occurs it wont ignite battery gases. Blowing up batteries is NOT fun especially when their still in the car & your leaning over them.
David

[Grant]

I keep one short jumper lead under rear seat and I mean short it is only 12 inches long goes pos on second battery to pos on dead battery and turn key
Also keep a long Heavy Duty set of leads under seat for all other dead vehicles

[Wooders]

BlackXJ, is that from the Factory Service Manual, the Owners Manual or a Haynes/clintons manual :?:

What I dislike about that approach is when connecting you connected bothe cabled to the boost battery first - so you have two live ends danging about and these can easily be dropped/touched causing an arc.

As for blowing up batteries - well theres a good reason to run a dry cell optima huh ;)

[wrench]

Nah Wooders.
Batery acid is a bit like used diesel oil. All good mechanics from the old days consider it good for the skin & complexion. To hell with all these new fangled gurus who tell us otherwise. Besides most poverty stricken spanner jockeys cant afford optima batter :roll: :lol: ies.

[Laz]

Have a look at the battery booster packs - they run a 12v sealed lead acid gel cell - these can supply some stupid amount of current for starting.

I saw one a supa cheap for $150.00 ~ ish -

[wrench]

I had one in the workshop for a while (not the supacheap crap). Was very handy but when it died we reverted to leads & battery. Found the pack almost useless if the battery was totally dead. Just didnt have enough CCA's, especially on diesels.

[wrench]

BTW. The best use was for running flouro lights when camping. Neat & convenient.

[blackxj]

Wooders I quoted the procedure from the Factory Service manual.

You are right about having two live ends you don't want to touch together I didn't include the warning to keep the procedure simple.

The warnings are:
WARNING: REVIEW ALL SAFETY PRECAUTIONS AND WARNINGS IN BATTERY/STARTING/ CHARGING SYSTEMS DIAGNOSTICS.
DO NOT JUMP START A FROZEN BATTERY, PERSONAL INJURY CAN RESULT.
DO NOT JUMP START WHEN MAINTENANCE FREE BATTERY INDICATOR DOT IS YELLOW OR BRIGHT COLOR.
DO NOT JUMP START A VEHICLE WHEN THE BATTERY FLUID IS BELOW THE TOP OF LEAD PLATES.
DO NOT ALLOW JUMPER CABLE CLAMPS TO TOUCH EACH OTHER WHEN CONNECTED TO A BOOSTER SOURCE.
DO NOT USE OPEN FLAME NEAR BATTERY.
REMOVE METALLIC JEWELRY WORN ON HANDS OR WRISTS TO AVOID INJURY BY ACCI-DENTAL ARCING OF BATTERY CURRENT.
WHEN USING A HIGH OUTPUT BOOSTING DEVICE, DO NOT ALLOW BATTERY VOLTAGE TO EXCEED 16 VOLTS.
REFER TO INSTRUCTIONS PROVIDED WITH DEVICE BEING USED.
CAUTION: When using another vehicle as a booster, do not allow vehicles to touch. Electrical systems can be damaged on either vehicle.
CAUTION: If the cause of starting problem on dis-abled vehicle is severe, damage to booster vehicle charging system can result.

[Steve F]

That jewelry one is something I missed when I was about 19. I had a RS2000 Escort that I used as a club racer. I was always very carfull when taking the battery out or puting it in (often). I always wrapped my hand around the end of the spanner so it wouldn't short on the other terminal, forgot I had a ring on. The inside of the ring touched the spanner and the outside touched the battery. The heat was so high it spot welded the spanner to the ring and burnt the crap out of my finger. I still have a bit of a scar and I'm 33 now!!! It amused my mates no end.

Cheers
Steve