X5 3.0d won't start

[omodos]

Thanks..made a pigs ear of it....will try again as you described tomorrow , you maybe right that my DMM isnt up to task but i was able to see reading by recording it and playing it back frame by frame...thanks once again

[wpoll]

Originally Posted by omodos

Thanks..made a pigs ear of it....will try again as you described tomorrow , you maybe right that my DMM isnt up to task but i was able to see reading by recording it and playing it back frame by frame...thanks once again

Not at all (love that phrase, btw!) - it is a little confusing.

And your trick of recording the meter is a great idea - I must try that. Don't know why I didn't think of it myself - I work with high-speed imaging!!

Here's an image that might help you understand this a bit better...



From this web site...

You are trying to determine the voltage drop across the positive cable (the red one) and normally you would place the meter as shown. On a X5 this is hard to do due to the cable length. Using the cigarette lighter socket gives a "near enough" value, as the cable feeding the cigarette lighter socket runs back to the battery (+) and as long as it isn't carrying any current, there will be negligible voltage drop on it.

[omodos]

Originally Posted by wpoll

Yep, as Andrew said - it'll still be close and work fine.

The circuit diagrams are a bit variable on the main B+ lead from the trunk (boot) to the firewall/starter/alternator - one diagram shows the cable as being 70mm sq. and another shows it as being 95mm sq.

That's a BIG cable!

Wpoll hi again, righto, this weekend had the little one in the shopping trolley and left the store, and noticed an identical x5 parked up next to me, driver in the seat radio on, car off, got the odd funny look when I asked for a favour... but when I explained what it was she was fine with it. Asked driver to start her x5 and it fired up with NO laziness at all, sounded better firing up even than mine even after I had immediately changed to a new battery...sooo kind of more than proof that my starter is pants.
Soooo father in law has insisted we take it to the best auto electric guys about see if he can recon etc (but go a feeling will be just the same buying a reconded desno off ebay) and at least I know in the uk they would have done it properly....will keep ya posted

[wpoll]

Sounds like another nail in the coffin for the starter.

[omodos]

Originally Posted by wpoll

Sounds like another nail in the coffin for the starter.

Bahh just want to get to the bottom of this cos spent ages looking to see if i had parasitic draw and didn't(who knows maybe have it now after testing few years ago) plus really don't want to be hooking up ctek as often as I am now


So far:
1.car started with jump pack attached -made some difference to laboured start but not whole lot

2.battery replaced gave better than above starts but after couple of weeks of my driving style, the starting starts to get labouored

3. so IF my amp clamp test was not flawed (i had clamp round one battery terminal and simply started car - on a fully charged good battery, amp clamp hit 392 for 1 sec and on second start clamp read 0L overload ie went over 400a then it does seem like starter, just simply drawing too much juice.


Even my crappy math's can suss this out, but correect me if I am wrong, so denso starter is rated at 2.0kw


I draw say 390a and at min 9.6v when starting 380X9.6 = 3.74.kw


not too sure why when hitting a figure above starter motor spec it just doesn't cut out....?mind you its only for a split second

[wpoll]

Originally Posted by omodos

...

Even my crappy math's can suss this out, but correect me if I am wrong, so denso starter is rated at 2.0kw


I draw say 390a and at min 9.6v when starting 380X9.6 = 3.74.kw


not too sure why when hitting a figure above starter motor spec it just doesn't cut out....?mind you its only for a split second

The thing to remember about electrical motors is they DRAW power - you don't PUSH it into the motor.

Your starter is (most likely) faulty and is drawing (sucking) about 3.8kW of power. The total draw is dependent on a few factors, including motor efficiency and load.

It's rating of about 2.0kW is actually the output power specification - when running correctly the motor can output about 2.0kW or "power" or "work".

If the starter motor was 100% efficient (and most aren't - ever) then it would draw about 2.0kW of electrical energy to generate 2.0kW of output energy.

As it's faulty, it's WAY less than 100% efficient, maybe as low as 30-40%. So it draws 3.74kW of electrical energy and only outputs somewhat less than 2.0kW of output energy - say it's only 1.5kw. This missing energy is the conversion loss in the faulty starter motor and is most likely being turned into heat (and a little light in the form of sparks!).

It also explains why your engine, which needs about 2.0kW of power to turn it over sounds like its slow to start with only 1.5kW driving it.

Make sense?

[omodos]

Crystal clear great write up cheers

[andrewwynn]

If you look at the video of the take apart of the damaged starter, notice that some of the commutator bars are melted together that will cause current to flow through more windings than designed at the same time. This will cause it to draw dramatically more current

You should be getting close to 11 v at the starter so 2000w would mean 180A (just a rough estimate. Actually, moronically they probably rate for 12v even though that theoretical value is not likely.

[omodos]

Originally Posted by andrewwynn

If you look at the video of the take apart of the damaged starter, notice that some of the commutator bars are melted together that will cause current to flow through more windings than designed at the same time. This will cause it to draw dramatically more current

You should be getting close to 11 v at the starter so 2000w would mean 180A (just a rough estimate. Actually, moronically they probably rate for 12v even though that theoretical value is not likely.

thanks for another response, well midday was at an autoelectrician who called my starter a sleepy one, "bring me another one I will swap it out" I asked if he could recon existing,he said yes, but am in two minds about doing a recon of existing one as surely replacing it altogether eliminates risk of him maybe using substandard parts/and or forgetting something during reconditioning old one....plus the current denso 2.0kw rated one better replaced with a 2.2kw ?even if the newer one ain't quite up to the standard of the denso (which going by the service it gave me ain't that good anyway). This herth+buss brand is a pretty new german registered firm for alternative car parts for european and japanese cars, i believe parts made in china. Debate about Chinese products is a whole new ball game for another day.