XSeries-forum

So last winter my X was a bugger to start in the cold. It turned over VERY slowly unless the battery had been charged overnight. The battery (less than a year old) drop tested just fine and the current draw once the car was in sleep mode was just a few mA. I changed all 6 glow plugs since 2 had failed and also changed the glow plug controller. I also changed the alternator brushes and diode pack. But still the problem persisted. It was hit and miss whether it would start at the end of the working day on very cold days. So as autum now approaches, I've decided to investigate the starter motor as the are many reports of older units drawing huge current. I removed it today and the casing is stamped with "Denso - made in Italy". This was disappointing as all references have stated that its the Marelli alternator that fails in the manner that draws huge current.

So my question is, shall I replace the starter with a new one even though it is Denso, not Marelli? Or am I wasting my money? Any thoughts will be greatly appreciated.

Have you tried to put a clamp meter on to see what amps it was pulling, I would have thought that if it was a starter motor problem it would have given you problems all year round. Maybe the alternator output is low, maybe someone has fitted a lower than spec alternator that can't keep up with winter demand. iE lights, wipers fans.

No I haven't used a current clamp. Couldn't find one to borrow. It is somewhat sluggish all year round but far, far worse when it's very cold. I checked the alternator rating when I replaced the brushes and diode pack (output was a little low at 13.8 volts) and it was the highest output rated on realoem.

So battery (Bosch S5) drop tests ok, alternator output is good. Negligible drain in sleep mode. What else is left other than the starter issue? I realise its unscientific not to use a current clamp but I didn't have one available and the local garages want to charge an hours labour for "diagnostic investigations").

A failing starter will draw well in excess of the battery CCA so becomes more obvious as it gets colder.  Mine drew over 900A but the BMW test rig said no problem UNTIL one of the Techs borrowed a current clamp and hey presto....but the battery topped out at 830A hence not being happy when the starter was engaged.

They aren't all Marelli units.  Some are Denso, and some are Bosch.  Why the variance I don't know, but it may be that BMW use whatever they can get when making the engines.

Richard

Okey dokey. But I'm left wondering if the fact I have a Denso starter as opposed to a Marelli means that I should rule the starter out of the equation. Are the other brands susceptible to the same problem? Even more clouding to the issue is the fact that Denso took over Marelli back in 2000.

I would have thought all starters are susceptable to failure as they are high current rotating devices.

If you have it out it would be worth while checking the basics - Brushes OK, insulation resistance OK and also the solenoid contact resistance.
High resistance on that contact (and we are not talking much) would affect starter efficiency.
You only need a few volts drop to cause it to struggle

Check all connections and earth points too, inc the mounting faces of starter to engine / Gbox.

I've had this problem with my '05 when I first bought it .
The stealer over here told me there were all sorts of errors codes which could contribute to the problem and
recommended that I should install a new battery to start with . This lasted 2-3 days before the same symptoms
returned . I lived with the prob for 3 wks before coming over to Blighty for X-mas , where I took it to my local Indy in Wolves . Without even putting a computer on he said 'it's a Marelli started,thats the cause' .
I've always had good relationship with them so I told them to change the starter motor if they were sure , which they did , and it cured the prob . When I went to collect it he told me they did a current draw test and it had gone off the scale of their test machine , over 1000A draw .

I know yours is a Denso , but I suspect they have similar reputation to Marelli , it'd be my first port of call and change to a Bosch , which is what I did and I've never had any prob since .

HEre is an additional suggestion. Do you know anyone else with an X5 who isn't having the same issue (ie they have a 'good' starter) - you could swap them and crank it over and see what happens. May rule the starter in/out very quickly....?

Just a thought
Smee

Starter motor now replaced with amazing results. It turns over sooooooo much faster even in this warm weather. I can't believe how sluggish it was in comparison.

[quote="ChrisLux"]

I've had this problem with my '05 when I first bought it .
Without even putting a computer on he said 'it's a Marelli started,thats the cause' .
I've always had good relationship with them so I told them to change the starter motor if they were sure , which they did , and it cured the prob . When I went to collect it he told me they did a current draw test and it had gone off the scale of their test machine , over 1000A draw .

I know yours is a Denso , but I suspect they have similar reputation to Marelli , it'd be my first port of call and change to a Bosch , which is what I did and I've never had any prob since .
[/quote]

Do you know the type or model number of the Bosch starter motor you had fitted to your X5? I'm sure a lot of e53 owners would be interested in a potentially more reliable Bosch replacement ?

Just ordered one from Eurocarparts for our E46 with the same problem.  Starter drawing 540A instead of 180A!

There's a surcharge of £120 to make sure you give the faulty one back.  Cost just over £228 with the surcharge.