Why wouldn't my Jetta TDI jump start off another car?

[cyrus buelton]

Disclaimer: I may not be the most mechanical individual, but I do know the basics of jump starting a car. I have done it many times prior to this weekend with 100% success.....jumping a car isn't rocket science.

So my wife calls me Wednesday while she is at work stating the car would not start, made a clicking noise when turned on.

ok, battery issue.

I have her find the local security guy at her work to give her a jump start. Car starts she comes home. The security guy used one of those starter units; not his SUV.

So the next morning.......car won't start. Ok, fine, needs a new battery. I'll jump it after work and get a new one at sears (140$ for a TDI battery).

I couldn't get this god damn thing started for the life of me. I used two sets of cables (thinking one of them was faulty). No luck.

Used two different cars, thinking there was an issue..........still no luck.


I am thinking what the make the beast with two backs is going on, maybe the battery isn't the issue. make the beast with two backs.

Call AAA, they come out saturday with their Battery Tech, runs his tests, battery is only cold cranking 300.....not good.

He gets out his starter unit.........make the beast with two backser starts right up. I am mesmerized at this point.

He sells me a battery, installs it, I pay him 149$ total........and I have a running car.


So why wouldn't it jump off another vehicle?

[red baron]

Cheap shitty cables they sell now don't carry much current.

Get yourself some single or double 0 copper cable and some quality clamps and make your own.

[cyrus buelton]

Cheap shitty cables they sell now don't carry much current.

Get yourself some single or double 0 copper cable and some quality clamps and make your own.

I was using a nice pair of copper cables.

I thought the original problem might have been the cables as the first ones I used were crap.

So I switched over to mine after I found them.

They are very good quality and have been used numerous time before.

[redxblack]

I jumped my wife's jetta and it cooked the computer onboard. My mechanic told me that the VWs need a full charge to kick over, which is why charger boxes work but cables don't. He said that IF I were to jump a jetta, I should leave the cables on for 45 minutes.

We fixed and then sold the Jetta for a toyota.

[cyrus buelton]

^

That is interesting.

Like hell I would let my car run for 45mins just to jump it!


When changing the battery, you have to keep the positive on a charger so it doesn't erase the code on the stereo.

[MendoDave]

Probably the battery in your other car wasn't up to the task of jumpstarting the VW with only 300 cranking amps, even though its starts your other car just fine. Its tough with a battery that worn out.

[corey]

it probably has a lot to do with the diesel system.
im not an expert on the subject by any means, but i would imagine that the glow plug requires a pretty good amount of juice, and that whatever is actually cranking the motor (starter) is going to need alot of power to get something with around an 18:1 compression ratio to crank enough to create combustion simply off of compression.
not an easy task...

[cyrus buelton]

Probably the battery in your other car wasn't up to the task of jumpstarting the VW with only 300 cranking amps, even though its starts your other car just fine. Its tough with a battery that worn out.

The first car I tried to jump off was a BMW X5; couldn't find the negative terminal under the hood and my neighbor had to leave, so we said make the beast with two backs it.

Moved to his roommates M3 (battery in trunk) and it wouldn't jump off that. He said that battery was less than a year old.

Tried to jump it off my Lexus RX300, new battery in December; not a chance it would start.

it probably has a lot to do with the diesel system.
im not an expert on the subject by any means, but i would imagine that the glow plug requires a pretty good amount of juice, and that whatever is actually cranking the motor (starter) is going to need alot of power to get something with around an 18:1 compression ratio to crank enough to create combustion simply off of compression.
not an easy task...

That's what I was thinking........just not enough juice.

However, I spoke with Ducatize and he claims it shouldn't matter. I am no expert in this area, so I haven't a clue.


It's just annoying to know that your car, if needing jumping, won't start off another car...........

[corey]

any clue why the battery died?

[cyrus buelton]

any clue why the battery died?

Bought the car new in May 2004..........

I think a little over 5 years on a OEM factory battery is pretty good


When AAA came out, they did a diagnostic test and my alternator was fine

[redxblack]

Just so that it's clear, my mechanic didn't want me to leave the cables on for 45 mins - he was suggesting not to jump a jetta w/ cables. We have AAA, so he suggested we use that if we needed it.

[Jarvicious]

The first car I tried to jump off was a BMW X5; couldn't find the negative terminal under the hood and my neighbor had to leave, so we said make the beast with two backs it.

Moved to his roommates M3 (battery in trunk) and it wouldn't jump off that. He said that battery was less than a year old.

Tried to jump it off my Lexus RX300, new battery in December; not a chance it would start.

That's what I was thinking........just not enough juice.

However, I spoke with Ducatize and he claims it shouldn't matter. I am no expert in this area, so I haven't a clue.


It's just annoying to know that your car, if needing jumping, won't start off another car...........

So does BMW put the battery in the trunk straight out of the factory or whas this a spare power source for a sound system?  Forgive me for asking the dumbest question of all, but the cars you were trying to jump from WERE running right? 

Other than that I'm sure corey is right in the diesel theory.  Those glow plugs are no joke when it comes to power consumption.  It's either that or those crazy Germans just forgot whether the + meant ground or hot.

[cyrus buelton]

So does BMW put the battery in the trunk straight out of the factory or whas this a spare power source for a sound system?  Forgive me for asking the dumbest question of all, but the cars you were trying to jump from WERE running right? 

Straight out of the factory on this M3, maybe a 2002 or something.

It sits in a compartment on the right side of the trunk.


My dad's old 91 audio quattro had the battery under the back seat

[mdriver]

So why wouldn't it jump off another vehicle?

Fahrvergnügen.

[Popeye the Sailor]

it probably has a lot to do with the diesel system.
im not an expert on the subject by any means, but i would imagine that the glow plug requires a pretty good amount of juice, and that whatever is actually cranking the motor (starter) is going to need alot of power to get something with around an 18:1 compression ratio to crank enough to create combustion simply off of compression.
not an easy task...

Sorta.


I did use a Ducati to jump start a TDI once. Took a while to get enough charge in that thar diesel, but it worked.