Car Battery Starting Issues - Temperature?

Every so often, our 1989 Jeep Cherokee would not start. Still cranked, didn't drain down to nothing upon cranking, just wouldn't turn over.

We took it in to our mechanic ... and he couldn't get it to crap it. Started fine every time, over a three day period. Of course, he explained that he could start replacing things, but that would be silly since it would just be a guess, and we might end up replacing something that was fine. So, we brought it back home.

Fine for a few days, and then after sitting in the parking lot at work, it cranked, but didn't start. We had bought a battery pack charger thing. Hooked it up for the jump, fine ever since. However, we did notice that the last few times it wouldn't start, there was a huge temperature swing. We live in the North - below zero in the morning and up to 60F or so in the late afternoon.

Coincidence? Could there be something to the temp thing?

2010-05-11T07:50:19Z

I should add - It's not at the *cold* end of a big temp swing day that it won't start. It starts fine in the freezing cold.

9 starts out of 10 are fine no matter what the weather is. It's just at the warm end of a big temp swing that it seems to have problems ... and then it jumps just fine.

2010-05-11T07:51:57Z

We do the fuel pump/computer thing every time - turn the key and let it run a few secs before cranking it. We've always done that. Doesn't help.

2010-05-11T07:59:52Z

Someone asked "Why the battery pack?" This is why - Because the battery pack makes it start. It seems like every so often, as I explained, it cranks, but not quite enough juice to turn over. The jump DOES start it when this happens.

Michael S2010-05-11T07:49:02Z

Favorite Answer

It could be temperature but I'm going to take a stab at what I've been noticing lately and I've been telling people.
Even though your's is an '89 with a rudimentary computer, I think if you got into your car, turned the key to the on position without starting, for at least a few seconds, it will allow the computer and the fuel pump to do their thing.
It's even hard for myself to change the idea of jumping in and starting right away. But it's worth a cheap try.

pedro7of92010-05-11T14:57:14Z

you said a lot..cranks but doesn't start..so why the battery pack??

reasons for hard starting,,,
1 its a 1989,,,that was a bad time 4 cars,,,is it fuel injected or a carb, either way injectors clog/leak carbs choke fails,,,,
2 ignition...plugs..wires,,,cap,,,rotor...all are good for 3 to 5 years [tops]
3 cold affects coil..wet cold weather gets into old plug wires [wipe with wd 40 or replace]
4 battery must have 12.7 volts at rest,, and always clean and tighten cables,,,
5 i feel bad for you and the mechanic,,,is it computer controlled or [BC..before computers] many younger mechanics are helpless without a computer to show the way...find a mechanic named crusty lol

Anonymous2010-05-11T14:44:48Z

could b temp sensor is bad.......they are designed to turn car off if vehicle over heats......so if sensor has gone bad and now when vehicle is cold sensor freezes and gives "overheating"signal to computer may b ur problem.....but just guessing ....