Problem with X5
 

For the last month or two, ever since the weather turned cooler, I have been having problems getting my 2008 X5 3.0si to start in the mornings. The battery is new and cranks perfectly but the engine just won't turn over. Sometimes it takes 6 or 7 tries, with a full minute of cranking, before it starts. I have taken it to the dealer twice but they can find no problems. In warmer weather, or in the afternoon, it usually starts on the first or second try, which is perhaps why they can find nothing wrong. But for years, this X5 started perfectly, first try, every time. The car is currently at the dealer and will stay for another week in the hope they can find the problem. Any ideas?

Thanks!

Pet Peeve: if the motor is cranking- ie "rotating" then it IS "turning over".

You mean it wont START.

Oh...I'd look at fuel pressures and maybe just replace the fuel filter prophylactically...maybe over the last 5 years the fuel flow has dropped a bit to now cause cold start issues.

Dealers are generally idiots who only look for codes and testplans these days. Yes, there are a few very good diagnosticians, but the odds that they will put one of those valuable guys on your little issue are low.

IMO

A

There was a thread on here earlier in the week addressing a similar issue. One suggestion was to change the plugs. I'm having a similar problem although not nearly as severe. I've ordered some and I'll let you know if it helps...

You say that the battery is new ... while it may be new, that does not mean that it is charged to the appropriate capacity to handle the complete load the car demands during startup.

Cranking power (CCA) of a battery is only one indication of the condition of a battery. That's why it can turn the starter motor. But, it also has to have sufficient reserve capacity to fire up all of the other electronics involved in starting the car. The reserve capacity of a battery is closely related to the Amp-Hour rating of your battery.

This is where things get interesting: if your battery is (recently) new and you or your dealer never registered and programmed the car's computer to recognize the new battery, then there is a good chance that you are either undercharging or overcharging the "new" battery. As your old battery ages, the intelligent battery monitor tells the alternator to put out more current. When you replace the old with new, the same amount of current will be pumped into the new battery. Either too much or too little is bad for the battery (over time). The end result is that you never charge the battery to its proper capacity and hence you end up with hard starting symptoms like you have now. The fact that you need to crank it 6 or 7 times is a good indicator that the battery is not at it's full capacity. Take the car back to the dealer and have them:
1. check the rating on your (new) battery
2. make sure the battery is properly registered
3. double check to make sure that the car is programmed for the proper Amp-Hour (Ah) rating of your battery.

BTW, doing this through the dealer can be very expensive!

Then, buy a Battery Tender and hook it up to the car on nights that it gets cold (40 deg or below) or if it is parked for more than 48 hrs.

Could be the crankshaft position sensor. My 07 4.8 had similar issues. Then, finally, I walked out from work one day to go home and it would turn over but never start. Then, I tried again and I got a transmission failure message. So, I called a tow truck and when the truck got to my office, I tried starting it one more time and it started up without any errors. I drove it right up on the flatbed and turned it off. Dealer replaced the crankshaft position sensor under warranty and it's been good ever since.

Interesting. I'd sat this has nothing to do with the OPs issue.... if you think it does, describe how this would impact STARTING (not CRANKING!!!!) and only when cold. Somehow the improper battery stuff you cite is impacting fuel or ignition...(yet it has plenty of juice to run the high current starter motor)..HOW?

HOW? Glad you asked ... it helps to be informed ... read pp 5 - 20 in the attached, especially p. 7 and p. 18

Yeah, I have that too.

I know you are excited about discovering about coding for your own battery...:thumbup:

but again, nothing in that document describes how your theory fits the OPs symptoms... plenty of cranking voltage, but issues with start (ignition or fuel)

(This theory that improper registration will lead to hard starts in cold weather is, well, lets say 'as yet unsupported'.)

And 100% agree it helps to be informed. :)

A


PS 99% of that document describes things that happen AFTER the car is RUNNING.

Agreed with you. Don't see how it related to OP problems. Beyond me, very confusing post.

It sounds like a fuel problem. I would investigate the fuel pump and injectors first. I had an issue with a bad injector that would slowly bleed down when the car was off for several hours. It would drop the fuel pressure and require longer time to start. In cold weather it was worse.

Really a had start issue should not be too hard for the mechanic to diagnose. Once he proves it will start, he knows it has compression, fuel/air and a spark. From there, he just needs to figure out why one of those components is missing at start up.

Check this out:

http://www.xoutpost.com/bmw-sav-foru...tml#post906410

Monitoring fuel pressure during cold start would b the way to test...but most modern BMW techs just 'look for codes'...

Ard,
I think we both cut our teeth working on motors with no electronics. It's amazing how much of the basics have been lost.

Thanks for all the suggestions, my X5 has been at the dealer for a full week now and they still have not diagnosed the problem. On Tuesday, they suggested replacing the fuel pump. Yesterday, they reconsidered and today they are monitoring fuel pressure. The battery is new and was installed by the dealer 10 months ago and they say it is fine. I am driving a loaner 328 but miss the Xman. Will update asap. Thanks again.

Latest word from repair tech..the fuel pressure regulator, which is internal in the fuel pump, is leaking down intermittently and that is causing the extended crank time.

Glad you got it fixed. I do not understand why this took so long to diagnose. There should be a schrader valve on the fuel rail. I would have tested fuel pressure with the vehicle off, then I would have gotten the vehicle running and tested fuel pressure. I do not know the BMW spec; but, I would expect it would be somewhere in the 45-55 lbs range. From there just hit the throttle, see fuel pressure rise 5 or so lbs (this tests pump performance). Pull the vacuum line, again we should see fuel pressure rise 5 lbs or so (this will test the regulator). Turn off the vehicle and wait 30 minutes or so, see how much pressure bled down. It should be nearly no change. Leave it overnight and check the pressure again. If the pressure bled down, you are losing fuel pressure.

A leaky injector will make for a hard start as well as the car running rich on one or more cylinders at start up. You may see black smoke. A bad fuel pressure regulator will allow the fuel to drain back into the tank, so you will not have the rich condition at start up. A quick check of the exhaust at start up and pulling the plugs will tell you.

Sorry for the long reply, it just bothers me that modern techs struggle with the basics. This is something that someone with basic mechanic skills should be able to diagnose.

Thanks very much for your detailed reply, you really know your stuff! Oddly, they havent actually fixed my car yet, I asked if the leaky fuel pressure regulator could be replaced without replacing the fuel pump but haven't gotten any response. Will post again when I hear something.

I enjoy working on anything with a motor. Been playing around with them from my first Rupp mini bike 30+ years ago. :D

I would expect that the pump and regulator are one piece. I would guess that it was a manufacturing decision.

The difficulty with modern diagnosis is more than meets the eye...

While we both said "monitor fuel pressures"...which indeed was the key, there is an economic factor at play.

You see BMWNA only pays the dealer for certain service codes- if a dealer spends 4 hours diagnosing a bad sensor, the "book" may only provide for 30 minutes to diagnose and repair- because the 'book' assumes a code will be set and the car will arrive with a bad sensor code already logged.

So dealers- and specifically the tech and the service manager- really dont like spending time to diagnose stuff that is outside the usual path. They have to document complaints a few times, then send it to BMW...then open a puma..then BMW says 'run these test plans'... all the while, BMW is telling the dealer what they will pay for the work they are asking. Practically speaking, these long drawn out problems are a lot of 'wait for PUMA to reply' then 'find time in the schedule with the other 20 cars I am clearing to do what they ask', then 'document results and send back'...rinse and repeat. BMWNA and PUMA control the work reimbursement and therefore control the pace of this stuff.

I post this so people can understand what motivates/restrains the tech/dealer... the key to managing a repair is to support the dealer when he is doing HIS job, (and kick butt when they arent)..but if you can show them you understand their challenges that are created by BMWNA, you buy some goodwill in the relationship

Not sure this WAS the issue here, but food for thought.

A

haha.

Honda Trail 70. 40 years ago.

Actually working on a pair of them now doing a restore!

I guess this explains why it's going to take 2+ weeks to solve what seems to be a fairly simple issue.

UPDATE: Finally picked up the X5 yesterday, new fuel pump installed. The car ran fine all day but when I went out this morning it started right up and then stalled out immediately. After several minutes of cranking, on the 4th or 5th try, it finally started and continued running. Is there anything else that could be causing this extended cranking?

Thanks!