Car would not start, then started an hour later
July 2, 2024 3:12 AM Subscribe
About a month ago, our car would not start. Called AAA to jump start, but when AAA arrived an hour or more later the car started fine.
The car was checked out by a highly rated mechanic a month later and they said there was no way to know what had happened unless it was happening at the moment. The battery is two years old and tested to be excellent, mechanic said.
Since then, it has been driven for short distances only. But it needs to be driven a long distance soon.
This is a highly regarded mechanic shop with hundreds of 5 star ratings, bit could there be a way to diagnose this episode actually so long after the fact?
The car was checked out by a highly rated mechanic a month later and they said there was no way to know what had happened unless it was happening at the moment. The battery is two years old and tested to be excellent, mechanic said.
Since then, it has been driven for short distances only. But it needs to be driven a long distance soon.
This is a highly regarded mechanic shop with hundreds of 5 star ratings, bit could there be a way to diagnose this episode actually so long after the fact?
"could there be a way to diagnose this episode actually so long after the fact?"
No. But you're probably going to get a lot of theories from non-mechanics.
posted by jonathanhughes at 4:23 AM on July 2 [1 favorite]
No. But you're probably going to get a lot of theories from non-mechanics.
posted by jonathanhughes at 4:23 AM on July 2 [1 favorite]
The mechanic is right. Lots of variables are involved here, and it appears to be a sporadic thing, so there’s just no way to accurately detect the cause without being there when it happens.
posted by Thorzdad at 4:27 AM on July 2
posted by Thorzdad at 4:27 AM on July 2
they said there was no way to know what had happened unless it was happening at the moment
Maybe ask the mechanic if there's any way you might be able to get more information on the spot should this happen again, like with a code reader as mentioned in this thread.
posted by trig at 4:39 AM on July 2
Maybe ask the mechanic if there's any way you might be able to get more information on the spot should this happen again, like with a code reader as mentioned in this thread.
posted by trig at 4:39 AM on July 2
No, but to provide one theory.....
Is there any chance you might have accidentally left the headlights on and unconsciously turned them off after you found the car wouldn't start and before AAA arrived? Batteries that have been drained down can sometimes recover slightly once the load has been taken off.
I have been in almost the same scenario. I parked somewhere and left the headlights on. A few hours later I went back to the car and realized my mistake. The car wouldn't start, so I called AAA for a jump. I turned the headlights off. When AAA showed up an hour later, they tried starting the car (as they always do) before attempting to jump it, and the car roared to life leaving me feeling pretty embarrassed.
posted by RonButNotStupid at 5:21 AM on July 2 [1 favorite]
Is there any chance you might have accidentally left the headlights on and unconsciously turned them off after you found the car wouldn't start and before AAA arrived? Batteries that have been drained down can sometimes recover slightly once the load has been taken off.
I have been in almost the same scenario. I parked somewhere and left the headlights on. A few hours later I went back to the car and realized my mistake. The car wouldn't start, so I called AAA for a jump. I turned the headlights off. When AAA showed up an hour later, they tried starting the car (as they always do) before attempting to jump it, and the car roared to life leaving me feeling pretty embarrassed.
posted by RonButNotStupid at 5:21 AM on July 2 [1 favorite]
Check the battery's ground cable. If it's loose or damaged it can make the car act like the battery is dead. If it's slightly loose or a minor fault it'll be an intermittent problem.
Then again, yeah, I'm not a mechanic. If you can't recreate it and the car passes a mechanic's inspection then I'd drive it long distance.. just have a backup plan like AAA.
posted by blnkfrnk at 8:30 AM on July 2 [2 favorites]
Then again, yeah, I'm not a mechanic. If you can't recreate it and the car passes a mechanic's inspection then I'd drive it long distance.. just have a backup plan like AAA.
posted by blnkfrnk at 8:30 AM on July 2 [2 favorites]
Battery cables or alternator would be my guess. Our mechanic checked our battery before a trip and our car still died. Super helpful mechanic found out it charged up at the start but dipped later below the required manufacturer specs. Have them run a 5 minute (or so) test on your alternator.
Of course the fix is to replace the alternator. $500-$1000 bucks is the estimated cost.
posted by The_Vegetables at 9:39 AM on July 2
Of course the fix is to replace the alternator. $500-$1000 bucks is the estimated cost.
posted by The_Vegetables at 9:39 AM on July 2
We had a similar problem and the third mechanic said basically "oh, I've seen this before on these model cars, I bet your __ connection is loose" and went and tightened it up. So that was cool. But also very impressive and unusual.
posted by Lady Li at 10:51 AM on July 2
posted by Lady Li at 10:51 AM on July 2
How old is the car? I used to have an issue with my '91 Jeep (this happened around 2002) that ONLY happened when I stopped at a corner store near my house on the way home from work, unless I was also getting gas in which case it was always fine. Mechanic claimed it was "vapor lock" and to get out and open and re-close the gas tank, which worked every single time.
I hadn't thought about it for years, until last month we were staying with a friend whose housesitting gig included a well-worn 2005 Gen 1 Prius, and it wouldn't start after shopping at the grocery store and my friend was like "shit, this has NEVER happened". I noticed the dashboard was lighting up just fine, suggesting it wasn't a battery problem, so I had him go pop the gas tank. Started right up.
Now, we debated on the way home how likely it was that there was some sort of vacuum in the tank preventing a start versus some kind of problem that self-resolves if you leave it alone for 45ish seconds. Hard to say!
But if it happens again, give it a try before you call anyone.
posted by Lyn Never at 11:07 AM on July 2
I hadn't thought about it for years, until last month we were staying with a friend whose housesitting gig included a well-worn 2005 Gen 1 Prius, and it wouldn't start after shopping at the grocery store and my friend was like "shit, this has NEVER happened". I noticed the dashboard was lighting up just fine, suggesting it wasn't a battery problem, so I had him go pop the gas tank. Started right up.
Now, we debated on the way home how likely it was that there was some sort of vacuum in the tank preventing a start versus some kind of problem that self-resolves if you leave it alone for 45ish seconds. Hard to say!
But if it happens again, give it a try before you call anyone.
posted by Lyn Never at 11:07 AM on July 2
IME, 90+% of "transient" car problems are heat related. Still, the mechanic should have at least hooked up the scanner to see if any codes are produced (or did he do that and found nothing of use?)
I am going to suggest a broken ground as well, if the symptom was no crank/no start. Heat expansion somehow forced apart the circuit that completes the starter power circuit. Once car cooled the circuit is fine.
posted by kschang at 11:31 AM on July 2
I am going to suggest a broken ground as well, if the symptom was no crank/no start. Heat expansion somehow forced apart the circuit that completes the starter power circuit. Once car cooled the circuit is fine.
posted by kschang at 11:31 AM on July 2
We experienced this intermittent start problem when we were a long way from home with two small tired children aboard. Turned out one of the two ignition keys was fritzed /out-of-battery.
posted by BobTheScientist at 1:30 PM on July 2
posted by BobTheScientist at 1:30 PM on July 2
I had a similar problem and I had just purchased a new car battery. For some reason it would start fine, but then - randomly - it refused to start on three separate occasions at the same gas station after I had filled my car.
It turned out that the gas station had a speed bump and going over the bump caused the not-quite-tight-enough clamp on the battery terminal to jiggle loose. Three times.
I tightened the battery cables and it never happened again. But I almost went crazy trying to figure out why this one gas station was keeping my car from starting.
I suggest buying a portable jump start booster kit. I bought one from Amazon and have used it myself about a dozen times and used it to help other stranded motorists even more than that.
posted by tacodave at 4:32 PM on July 2
It turned out that the gas station had a speed bump and going over the bump caused the not-quite-tight-enough clamp on the battery terminal to jiggle loose. Three times.
I tightened the battery cables and it never happened again. But I almost went crazy trying to figure out why this one gas station was keeping my car from starting.
I suggest buying a portable jump start booster kit. I bought one from Amazon and have used it myself about a dozen times and used it to help other stranded motorists even more than that.
posted by tacodave at 4:32 PM on July 2
Unfortunately, you haven't given enough information for anyone to remotely be able to help. Specifically, why did the car not start?
Did the engine not crank over? Did it crank over but not start? These are very different things.
Assuming it did not crank over (or not fast enough to start, at least), your mechanic is right in that there's no way to diagnose an intermittent fault unless they can see it happen. In some cases, they would be able to see a fault code by plugging into the car, but some intermittent faults won't trigger a code. If they are as reputable as you say, they will have checked for fault codes.
If your battery is two years old, I would be suspicious of it, because it's, at best, close to its expected end of life. I'm always pleased to get more than a couple of years from a battery but 2-3 years is really all they're good for. I've just replaced the battery in my car at 2.5 years old because it was failing to provide enough power to start the car intermittently. It tested fine just after it had been charged by a charger or the car itself, but dropped slightly overnight and slowly dropped from there. My car is a diesel and requires more power than a petrol engine to crank over, which means it's also more susceptible to a weak battery, though.
I wouldn't be worried about driving a long distance, but I would have at least jumper cables and preferably a jump pack (both are good things to have anyway).
posted by dg at 11:31 PM on July 2 [1 favorite]
Did the engine not crank over? Did it crank over but not start? These are very different things.
Assuming it did not crank over (or not fast enough to start, at least), your mechanic is right in that there's no way to diagnose an intermittent fault unless they can see it happen. In some cases, they would be able to see a fault code by plugging into the car, but some intermittent faults won't trigger a code. If they are as reputable as you say, they will have checked for fault codes.
If your battery is two years old, I would be suspicious of it, because it's, at best, close to its expected end of life. I'm always pleased to get more than a couple of years from a battery but 2-3 years is really all they're good for. I've just replaced the battery in my car at 2.5 years old because it was failing to provide enough power to start the car intermittently. It tested fine just after it had been charged by a charger or the car itself, but dropped slightly overnight and slowly dropped from there. My car is a diesel and requires more power than a petrol engine to crank over, which means it's also more susceptible to a weak battery, though.
I wouldn't be worried about driving a long distance, but I would have at least jumper cables and preferably a jump pack (both are good things to have anyway).
posted by dg at 11:31 PM on July 2 [1 favorite]
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posted by ojocaliente at 3:18 AM on July 2