Intermittent Starting
 

Alright so I have a 2002 E53 3.0i which occasionally won't start. The issue seems to stem from the positive battery cable as usually after a jiggle it some I can get it started. I really don't mind this however it is a slight pain because I have a subwoofer installed in the back along with an amp. Now before anyone blames the subwoofer I had it professionally installed and I've checked the fuse and all connections in the rear and they seem to be completely fine. If anyone else has had this same issue and found a fix, I'd love to know. Thank you :thumbup:

Usual suspect of intermittent starting is usually the fuel pump relay in the glove box. It gets progressively worse and eventually not start at all showing similar symptoms of a weak battery.


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When you "jiggle" it...what exactly are you jiggling or moving? Is the clamp around the positive battery terminal moving...or are you moving the positive battery cable only?


If you can "jiggle" the positive battery cable and it is loose enough to move around the positive battery terminal...then your cable needs to be tightened (at the least). :)

When you say "Won't Start" is it the engine not turning over, or the engine cranks (turns over) but the engine does fire?

You got to be more descriptive in your assessment of the issue.

I have seen more issues caused by "Professional Installers" because they don't understand the electrical, communication systems install in various cars.

Sorry about that, I mean that when I turn my key and it reaches the 3rd position all I get is a single click and all of my electronics come on but no crank or start. As for the installation of the sub and amp I trust the shop as I’ve had them do work before, as well all of the connections are tight and free of corrosion. Also, if it doesn’t start, It will always start with a jump.

I checked the terminal and it’s tight and doesn’t move at all. I mean more that I grab the red cable and move it around a bit and then try to start, it doesn’t always work the first try but it does eventually.

Either completely coincidence having nothing to do with the battery terminal and most likely the problem is in the steering column: ews antenna or ignition switch (or faulty key) else something could be wrong with the BST at the battery.

Next time It fails see if you have voltage at the jump point in the engine bay. If no voltage most likely failure at the BST contact that is somehow opening and closing. If you have voltage at the B+ under the hood the problem almost certainly is key related: switch/ews/key.

Try the other key. If the problem goes away likely bad solder joint on the ews in the key there is a guy will fix for $60

Could it be a weak battery? Turning the ignition switch only hearing a click usually mean a weak battery. Using a jump pack at the engine battery jump terminals to start usually indicate a weak battery.

An alternator not alternating to charge the battery could be the reason for the weak battery.

Yea if you are hearing clicks then I would first assume battery for sure.




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He's said it eventually will start when jiggling the battery cable. Also that it goes from start to click no mention of slow turning start. It feels like key such to me

Negative cable or positive cable?

Could be a dirty terminal.

Definitely can be. He said was tight and terminal/s? are clean. I suspect the jiggle had more to do with taking time as he also said that enough attempts it will always start except also mentions jump starting which is confusing.

If the engine crank when the positive cable is jiggled, it could be the BST connector. Have the X5 been in an accident?

You can use an ohm meter to see if there is continuity between the connector and along any length of the positive cable (you may have to use a sharp pick to prick a hole into the insulation and check the continuity).

Here's a video on just replacing the connector and not the entire positive cable.

https://www.youtube.com/watch?v=kXk4CqD8q2A

It is 100% not the battery lol it is a SINGLE click as I stated earlier

Not the key, both have the same issue. If it were the ignition switch wouldn't my accessories not work? and wouldn't it not always start with a jump? Also when it won't start, voltage at the B+ is very low, below 1.

It hasn't been in an accident since I've had it, in fact I've never had an accident. If it were in an accident before I owned the vehicle I am unaware of I'll have to check.

Incorrect. When an ignition switch fails the most common symptom is that you get inconsistent starts. There are several parrallel switches inside the switch and the starter switch component is a common failure point and exhibits exactly your symptoms when it fails.

That being said, B+ volts low means battery problem. If B+ is low then it's not logical it would ever recover from that and start without a jump unless you have a connection problem somewhere.

If you have a defective battery it can cause very quick drops in battery voltage. I had a battery that would test fine, 550 cold crank amps, start the car at 0°F more than once no problem.

However, if I left the hazards blinking for 8 minutes I would not be able to start the car I would get one click. At that point I would get a very low vBat and would jump start easily.

My case turned out to be a defective battery (shorted plates or something: it effectively had nearly no AH capacity)

New battery fixed it right up

Intermittent Starting
 

Single click is what you'll get with low bat on the X5 in my experience.

I happened very quickly and recovered quickly. If you can start every time with jump start you have just determined red problem is either the battery or cables from the battery. (Can be a secondary symptom from the starter going and taking too much current).

How old is the battery?

You said that B+ is below one volt when the problem presents. Next time it happens, measure voltage from B+ to ground then measure the voltage at m your cigarette socket.

If you have no volts at B+ but normal (12ish) at the cig lighter, then your problem is either cable or terminal or BST.

Jiggling battery cable having an effect indicates likely a failure at the BST. How that would fail without an accident is very puzzling but it could have been "blown" but DIY repaired improperly.

So get it to fail then take some measurements:

VBat at battery, at B+ under the hood, cig lighter and from cig lighter to B+ under hood. (That should read about 0.05 to 0.15 v)