why will my car go from a running car but not a jump pack??

[carsnstuff]

my old c200 cdi keeps doing this thing were it wont start and i suspect the front SAM. it will always go from a running car but not a jump pack.

[dunc_sx]

Can only be down to getting more juice from the car surely?

[Matt Clay]

Monkey see, monkey do.

[carsnstuff]

^^^ monkey type.

[P. ONeill]

Not enough juice in the jump pack.

[Gary C]

Matt Clay said:

Monkey see, monkey do.

Surely Occam's razor is more appropriate

[carsnstuff]

must be the voltage. the jump pack was 1200a and fully charged and it wouldnt have any of it... my m8 just jumped it from his 18v makita drill battery.

[Aunty Pasty]

It's not the capacity of the jump pack you should be looking at but the starting and max current it can deliver.

For example, mine has a capacity of 18,000mAh but has a starting current of 300A / Max current 600A.

[Griffith4ever]

I suspect the 1200a he refers to is "amps" - i.e. lol , Sounds like a duff jump pack that is also overrated.

I have one (A lithium one) and it'll start a V10, tested, and I've started an M5 V8 amongst others - it doesn't even break into a sweat.

[Dogwatch]

It’s a diesel. Needs lots of cold cranking amps which the jump start hasn’t got.

[Griffith4ever]

.... and an 18v Drill battery has?

I reckon his jump pack is duff.

When functioning well, the lithium jump packs kick out one hell of a lot of current.

[carsnstuff]

Griffith4ever said:

.... and an 18v Drill battery has?

which its why its the voltage.

found the problem thanks to this vid. my car does exactly the same...

https://www.youtube.com/watch?v=PQCo7GRNxqg

there is probably a dodgy track on the PCB in the ECU that goes to that relay and the extra voltage from either the alternator circa 14v or the drill 18v is just enough to push it across. stands to reason right?

anyway dont have to jump it anymore thanks to that vid.

[Ouroboros]

When this happened to me it was the starter motor going.

[Griffith4ever]

carsnstuff said:

Griffith4ever said:

.... and an 18v Drill battery has?

which its why its the voltage.

found the problem thanks to this vid. my car does exactly the same...

https://www.youtube.com/watch?v=PQCo7GRNxqg

there is probably a dodgy track on the PCB in the ECU that goes to that relay and the extra voltage from either the alternator circa 14v or the drill 18v is just enough to push it across. stands to reason right?

anyway dont have to jump it anymore thanks to that vid.

I was replying to "t’s a diesel. Needs lots of cold cranking amps which the jump start hasn’t got."

So I replied indicating that a makita battery also does not have lots of cold cranking amps (and jump packs have oodles btw)

Doesn't matter how many volts you have if you don't have current (amps).

Glad you got it sorted.

[carsnstuff]

Oh right got ya

I havnt got it sorted yet ha... I just know what the problem is now and don't have to jump it everytime it misbehaves

[Polly Grigora]

carsnstuff said:

Griffith4ever said:

.... and an 18v Drill battery has?

which its why its the voltage.

found the problem thanks to this vid. my car does exactly the same...

https://www.youtube.com/watch?v=PQCo7GRNxqg

there is probably a dodgy track on the PCB in the ECU that goes to that relay and the extra voltage from either the alternator circa 14v or the drill 18v is just enough to push it across. stands to reason right?

anyway dont have to jump it anymore thanks to that vid.

No it doesn't stand to reason, increasing voltage from 12 to 18 won't enable the voltage to conduct across an air gap (broken PCB track)

If a PCB track was damaged by corrosion due to moisture getting into the ECU then there is a possibility that increasing the voltage will allow enough voltage to travel through the corrosion and pull-in a relay. 12 volt relay pull-in voltage will be approximately 8 volts

If the above is happening and there is corrosion within the ECU its days are numbered

Where in the video are ECU tracks mentioned?

OK seen the correct video now

Edited by Polly Grigora on Monday 11th July 15:48

[carsnstuff]

SORRY WRONG VIDEO!!


here is the right one... not my video but the symptoms are exact


https://www.youtube.com/watch?v=MyBE5BKk1O0

[carsnstuff]

but yeah anyway you are right griffith4ever that is probably what has caused it

[Polly Grigora]

carsnstuff said:

SORRY WRONG VIDEO!!


here is the right one... not my video but the symptoms are exact


https://www.youtube.com/watch?v=MyBE5BKk1O0

Thought there was something wrong with the video link

See where you're up to now. If your relay does the same as the relay in the video, it proves there is less than approx 7.5 to 8 volts across the relay and it won't pull-in but there is more than approx 1.5 volts which is enough to hold it in once the armature has been closed by hand

Good luck in finding the fault, it's a goodun