X5 3.0d won't start

[omodos]

Originally Posted by andrewwynn

Thanks and that would be awesome to have a diesel example. I've been wanting to get this concept of there ever since I read about the exponential growth of current draw as a starter wears out. Since many of not most DIY car fixers have a DMM and with the X5 having two separate paths for electric flow from the battery it makes this trick possible.

The cig socket gets its power from the feed that comes up the right side of the car, the starter gets the power from the big cable that goes up the left side past the B+ jumper and the alternator.

I'm not sure what power is cut off during the start but it's possible the value can be thrown off if something like the fan or wipers was drawing power up the right side. That said this technique should work very well to get a read on the starter current. I don't think the diesel or V8 has a thicker starter cable (which would change the 285 factor)

@Andrewwynn and wpoll, I think I have hijacked this initial post so apologies, please see the crude diagram tell me if I am on right lines...dv will be set to 12v dc of course
PS on my diesel the starter is pretty much behind the alternator and not sure the B+ feeds straight to alternator(generator as it is called here) or the starter

[wpoll]

Originally Posted by wpoll

I have the same (well, very similar) meter, Andrew - I'll do the test on my 3.0d and post up the numbers here.

Great work!

Didn't get this test done this morning, sorry - torrential rain here and 7DegC. - not great conditions for such a test...

[wpoll]

Originally Posted by wpoll

Didn't get this test done this morning, sorry - torrential rain here and 7DegC. - not great conditions for such a test...

So I tried to get a reading tonight - no luck. I thought at least one of my meters had a peak hold voltage setting (or min/max) but they don't, and the start is so fast it was impossible to get any reading.

I have a Fluke ScopeMeter at work so I'll have a go with that next week - darn sure that has a peak hold (min/max) and even graphing/logging I think...

[omodos]

Originally Posted by wpoll

So I tried to get a reading tonight - no luck. I thought at least one of my meters had a peak hold voltage setting (or min/max) but they don't, and the start is so fast it was impossible to get any reading.

I have a Fluke ScopeMeter at work so I'll have a go with that next week - darn sure that has a peak hold (min/max) and even graphing/logging I think...

ANY Fluke surely more accurate than my digital voltemeter...plus there is noooo setting on my device to hold peak/min, so as mentioned if i can will have someone recording the device while i crank key, then check out recording in slower motion.....end of the day still need to know if my starter is doing odd things. IF all is in order owe you fellas an apology or dram or two.Then I reckon will be investing in a agm as I dont think that its a coincidence agms are in all modern stop start vehicles as opposed to 'normal' batteries. All will be revealed soon

[omodos]

Originally Posted by wpoll

So I tried to get a reading tonight - no luck. I thought at least one of my meters had a peak hold voltage setting (or min/max) but they don't, and the start is so fast it was impossible to get any reading.

I have a Fluke ScopeMeter at work so I'll have a go with that next week - darn sure that has a peak hold (min/max) and even graphing/logging I think...

Wayne?wpoll? ok well wired up my basic dmm to the + in engine bay and the other probe touching the inner sides of the dc lighter socket, set it to 20V got a reading that looked ok for battery at rest 13.0V, cranked engine, dropped down to 8.98V....not sure how I am gonna get the amp draw of starter via this info? if it was my starter an issue would it have dropped much more than this

[omodos]

Ok sir thanks again will stick the probe into cig lighter socket..the other probe connect with a plastic peg to B+ set meter to 12v start car whist having someone record meter...will get back to you later on some of the maths but your explanation is much appreciated even though my brain is literally in sleep mode...

[wpoll]

On the diesel, it looks like the B+ runs right to the starter first, then hops over to the alternator...



https://www.newtis.info/tisv2/a/en/e...erface/hORvXOt

[omodos]

@wpoll, so we can still use andrewwynns trick to test the starter draw via the dc lighter and B+?

[wpoll]

Originally Posted by omodos

@wpoll, so we can still use andrewwynns trick to test the starter draw via the dc lighter and B+?

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!

[omodos]

Ok Wpoll appreciate yet again response, so basically should see a voltage drop on digital voltmeter from 12v or whatever battery will be reading down to 0.whatever on startup...hope nothing fries