Car won't start on hot days

[WolfBMW]

Hey guys, I did some quick searching and didn't see my exact problem, but it's probably out there somewhere so I'm sorry if I missed a thread somewhere around here!

A couple weeks ago I was coming home from work and the car wouldn't start; turning the key didn't do anything (no sounds). I happened to have parked facing down a hill, so I just popped the clutch and drove home. After that it started up fine for a while so I figured somehow the battery had been low and didn't worry about it. Then it happened again and I hadn't parked as luckily, so I waited a minute and tried starting it again and voila!, it started up fine.

This happened again today, and I've been parking with clear path downhill since last time, which is a silly way to live I know. But I decided to give it a minute rather than getting going with the clutch start and it successfully cranked, exactly like last time.

I mentioned hot days in the thread title because it's happened on 3 of our hottest lately, when I had to park in full sun in an overflow lot. (Today it was ~100 there). Maybe that's not relevant, I dunno, it just seems like a pattern to me. Any advice is appreciated!

[Oli77]

Strange cause batteries usually die on colder days or when winter picks up. That may not overrule a dead battery. When mine died, everything still worked in car except for the starting the engine part.

[BCS_ZHP]

Wolf,
How old is your battery? If it's a BMW battery, look on top of the terminal posts and the 2 digit week of the year and 2 digit year will be stamped in it. Of it's any older than 5 years old, I'd suspect your battery is weak and about to fail completely.
Bruce

[Hornung418]

If it doesnt crank it is most certainly your battery. Get it replaced. I have a Duralast something or other from AutoZone. I shall report back when I actually check the battery LOL.

Sent from my GS3.

[az3579]

I had this exact issue last winter when temperatures were in the single digits. Only when the temps were in the single digits, the car wouldn't start on the first try. I'd try to start it but nothing would happen after turning the key. It was not the battery as that was only a few months old. I replaced the fuel pump relay, ignition switch, and another relay (forgot which one) and the car started every time afterwards. From what I'm told, these are common failure items and wouldn't jump to a battery right off the bat. If the battery was at fault, I'd think it would at least try to crank before conking out...

I'm fairly confident it was the ignition switch that fixed it for me.


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[ELCID86]

Any update Monroe? Seems like if it was the battery it would at least try to turn over. Advance or Autozone will run a free diag. test on it.

[Oli77]

^ My engine did not turn over once when my battery died. This is very different from all the other cars I have owned that do try to turn over the engine even though there is not enough current to start her up.

[johnrando]

I'd certainly check the battery as others mentioned.

I've also heard on other cars of a fuel vapor lock issue on hot days... no idea at all if that's relevant here, just wanted to mention it. Hope you figure it out, and definitely keep us posted.

[WolfBMW]

I'm gonna go get the battery tested at Autozone tomorrow to see if that's the problem. It's ~4 years/50k miles old, so we'll see. Thanks for the advice, all!

Interesting to know that yours wouldn't try to turn over either, Oli, because that's what seemed kind of weird about it to me. It's funny that it won't try at all and then will start up fine a minute later. But maybe that's how it goes sometimes!

[BCS_ZHP]

Electrical stuff (like computer coding), you can't see it or get your fingers greasy on it, its not tangible and I'm a tangible type of guy, it's a mystery to me and I accept that there are electrical gremlins that I'll never understand.

[WolfBMW]

The check said my battery was bad, so I went ahead and replaced it. Hopefully that was the issue, time will tell!

[BCS_ZHP]

Could someone please get Charlie to post a pic of the lone sticker on the rear window of his car? OFR!

[cakM3]

Could someone please get Charlie to post a pic of the lone sticker on the rear window of his ///M? OFR!

Here you go Bruce :thumbsup

My ZHP
http://img.tapatalk.com/d/14/07/11/vu6a8y7y.jpg

My ///M
http://img.tapatalk.com/d/14/07/11/u4ubezav.jpg

Both cars have this sticker mounted, not because these cars are old, but because the owner of these fine specimens is ;) Got my AARP invite mail to prove it :p

[BCS_ZHP]

TY! In cold weather weak batteries will normally give signs of weakness, in warm weather they can just crap out with no warning. Maybe one of the smart engineers can explain it, I understand it but can't put it into words.

Congrats on getting it fixed Monroe!

[cakM3]

From what I understand car batteries when they get older (~4 to 5yrs) they don't hold their charge anywhere as good as they did when brand new. It has to do with the chemical compounds inside the battery (cathode and anode components). Over time they begin to lose their properties and as a result are not as efficient in storing energy. Over time, this may lead to the battery not holding enough charge so it will not perform well with any big change in temperature. I'm sure there are guys out there who can do a better job at explaining battery efficiency....I'm still dealing with a serious sinus infection so I'm still whacked out so to speak...

One thing to keep in mind however is that just because you're buying a brand new battery, you still don't know it's shelf life is. In other words, since being produced, how long has that battery been on the shelf? Once the battery has been built, it's shelf life starts. If you have a fairly new battery based on build date then you can pretty much rely on this battery for another 4 to 5 years....that's pretty much the average cycle of car battery life.

[az3579]

4-5 years is reasonable with Genuine BMW batteries, but from my experience with aftermarket ones, you'll be lucky to see 3.


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[WolfBMW]

Haha, nice stickers, Charlie.


Interesting to know about the effect of different weather extremes on the battery! I found some more info on Howstuffworks... reasons to appreciate taking Intro E&M this summer :)

[WolfBMW]

This bit:

The "self-recharging" features of batteries is most noticeable in a car battery. In some cases you can crank the engine until the battery seems totally dead, then come back an hour later and crank it again. The higher the drain on the battery (a car's starter motor is an incredibly high-drain device!), the greater the effect.
To understand why this happens, it is helpful to understand what's going on inside the battery. Let's take the simplest zinc/carbon battery as an example. If you take a zinc rod and a carbon rod, connect them together with a wire, and then immerse the two rods in liquid sulfuric acid, you create a battery. Electrons will flow through the wire from the zinc rod to the carbon rod. Hydrogen gas builds up on the carbon rod, and over a fairly short period of time coats the majority of the carbon rod's surface. The layer of hydrogen gas coating the rod blocks the reaction occurring in the cell and the battery begins to look "dead". If you let the battery rest for awhile, the hydrogen gas dissipates and the battery "comes back to life".
In any battery, be it an alkaline battery found in a flashlight or a lead acid battery in a car, the same sort of thing can happen. Reaction products build up around the two poles of the battery and slow down the reaction. By letting the battery rest, you give the reaction products a chance to dissipate. The higher the drain on the battery, the faster the products build up, so batteries under high drain appear to recover more.

And this:

http://electronics.howstuffworks.com/everyday-tech/blood-battery.htm


...now I'm officially distracted from my homework.

[johnrando]

Lol. Good stuff btw.

[cakM3]

Haha, nice stickers, Charlie.

Glad you liked them Monroe :biggrin

[Oli77]

News?

[WolfBMW]

Nope! All is well. My habit of parking in spots where I can roll start it on my own has not yet worn off, but we all have our little eccentricities.

[Oli77]

:facepalm Duh, after rereading the thread, I now realize you had bought a new battery.

[WolfBMW]

Welp, it wasn't the battery. Guess I'll go back to trying to figure this out when I get back from Italy in 3 weeks.

[ryankokesh]

I have three guesses:

1) clutch switch
2) key RFID thingy
3) starter relay


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[az3579]

I had this exact issue last winter when temperatures were in the single digits. Only when the temps were in the single digits, the car wouldn't start on the first try. I'd try to start it but nothing would happen after turning the key. It was not the battery as that was only a few months old. I replaced the fuel pump relay, ignition switch, and another relay (forgot which one) and the car started every time afterwards. From what I'm told, these are common failure items and wouldn't jump to a battery right off the bat. If the battery was at fault, I'd think it would at least try to crank before conking out...

I'm fairly confident it was the ignition switch that fixed it for me.


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Just leaving this right here...

[ryankokesh]

Just leaving this right here...

It would crank if it were the fuel pump or fuel pump relay, no?

Good call on the ignition switch, though.


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[az3579]

It would crank if it were the fuel pump or fuel pump relay, no?

Good call on the ignition switch, though.


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Don't know. I did all the relays and ignition switch at the same time because I didn't want to spend time troubleshooting in single digit temperatures, so I just suffered once.

I did all of them because my friend says they replace them at his dealer all the time.