BMW Is a No Go
October 19, 2009 2:40 PM   Subscribe

BMW 530I will not start.

My mother owns a 2003 BMW 530I with very very low miles.
She drove the car yesterday with no Check engine lights and no issues starting it up. Today she tried to start it up and nothing happened (engine didn't try to turn over no clicks from the solenoid nothing) She called AAA who thought it may be a battery but when they got there they said it had a full charge (all lights, stereo etc all came on). She currently has it at the Shop but i thought i would do a little investigation for her. Shes older and the Repair shops tend to inflate repair costs for her generation in that area (South Florida) cause their patrons don't often know any better then to accept what they are told.
posted by slowtree to Travel & Transportation (15 answers total)
I'm assuming there's enough gas for the spark plug to ignite?
posted by dfriedman at 2:45 PM on October 19, 2009

Did the accessories (stereo, lights, etc.) cut out when you tried start it? If they cut out, then your battery is too weak to start the car. If the accessories all stayed on, you have some kind of other electrical or starter problem. Not easily diagnosed over the internet.
posted by knave at 3:04 PM on October 19, 2009

It's not gas. The starter motor would turn the engine over regardless of how much gas was in the car, assuming the electrical system was in tip-top shape.

Just off the top of my head, does she have a different key for the car? Some BMW models have an anti-theft device in the key that the computer has to recognize to engage the starter motor. If her key were defective, it might not let the starter even turn over. Also, with the key turned and brake set, run the gear selector up and down it's range, in case the switch that doesn't let the engine start while in drive is stuck.
posted by hwyengr at 3:23 PM on October 19, 2009

Bad starter motor. Short between the starter and the distribution bus. Something along those lines. Not thinking it's a key problem - I had a key with the wrong electronic signature on it for my last car. It'd unlock the doors, even turn over the engine - but two seconds later the computer would shut it back down.
posted by squorch at 3:40 PM on October 19, 2009

Did she, or they, try jimmying the battery contacts or cleaning them? This exact thing happened to my girlfriend's 2001 Hyundai Accent. Still happens occasionally, but all it takes is a quick hood pop and a jiggle to fix.
posted by InsanePenguin at 4:45 PM on October 19, 2009

Probably either the starter or the engine immobilizer. You gotta take it to a dealer or mechanic.
posted by milinar at 5:04 PM on October 19, 2009

The same thing happened to my mom in a similar BMW and it WAS the battery. The local Joes couldn't diagnose it so she had it towed to the dealer they popped a new battery in and that was it.

I'm not much of a mechanic anymore, but I think it has something to do with the battery having and registering enough volts/12 for the radio etc. but not having enough amps to turn the engine over.
posted by snsranch at 5:29 PM on October 19, 2009

Could be a faulty ignition switch, which is common on the e39. The car has a system that senses a microchip in the key, which allows the engine to start. There could be a fault here. The key is charged by the ignition, but I doubt a dead key would cause this. Battery is inside in the trunck, so unless it's in need of replacing, it's probably okay---worth a look anyway.
posted by luckypozzo at 5:34 PM on October 19, 2009

Milinar wins for accuracy and brevity.
posted by davejay at 5:38 PM on October 19, 2009

Possibly a blown fuse? There's the ignition fuse in my car and if it blows it won't even turn over but everything else works. I can even honk the horn in frustration and blast tunes while I wait for the tow truck before I knew about that fuse.
posted by KI6ILS at 6:02 PM on October 19, 2009

2003 BMW 530I with very very low miles.

Smells like battery to me.

Elderly car owners, low milage, short trips around the neighborhood, age of the battery, it's all adding up to battery. Six years is old-ish for a maintenance-free battery (the type in all new cars). Combined with low mileage and likely short trips results in a battery that doesn't get a whole lot of time to charge up. Honestly, I'm surprised it lasted this long.

Other things, like fuses or relays might be at fault, but they're less likely. Typically, a failing relay will start as an intermittent fault and gradually get worse (not what you've described). I'd be really surprised if it was something like this. And I'd be stunned if this car needed a starter.

AAA might not be comprehensive in their battery diagnosis. They might just check for 12v and assume it's ok. For all you know, the battery might have 12v but less than a hundred amps, not nearly enough to get that car fired up.

If she's at the dealership, they'll probably have a battery tester that spits out a little receipt paper with the stats on the battery, like voltage, amperage, and the tester's diagnosis. If they've condemned the battery, they might have a print-out that they've attached to the repair order, or at least be willing to share with you.
posted by Jon-o at 6:32 PM on October 19, 2009

Short between the starter and the distribution bus.

My guess as well.
posted by Civil_Disobedient at 6:56 PM on October 19, 2009

When this happened to me a year or two ago, it turned out to be a bad ignition switch (where you stick the key) and a bad clutch pedal interlock (manual transmission, must press clutch down to start car), simultaneously.
posted by intermod at 7:47 PM on October 19, 2009

It could be a bad battery cable or a bad cable connection.
posted by rfs at 8:29 PM on October 19, 2009


Try measuring the voltage on the battery while starting the car. If it goes down much below 10 V, it's probably the battery. If it goes down to something ridiculous like 2 V, it's definitely the battery.

This happened on the wife's Taurus. Turned out there was a bad cell in the battery. It would allow a certain amount of current draw, but as soon as current demand got above a certain threshold, the voltage would drop dramatically. We couldn't even jump start the car. New battery and it was fine.
posted by Doohickie at 9:03 PM on October 19, 2009

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