[MCL968]

Check another car with the voltmeter before you start replacing parts. The symptoms don't add up for me.

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[flash]

while it would be prudent to verify it, the low voltage reading is a perfect indicator of the problem.  the symptoms are pretty simple.

 

the meter on the dash is all but worthless.  it is known to be off on a good half of the cars.  usually it reads low, but i've seen it read high too.

 

yes, there could be GSS, but i think it's time for occam's razor here guys.  low voltage plus slow cranking is probably a charging system issue

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[ds968]

I'll check the other cars batteries in about 15 minutes , for good measure . So as I previously said although my mechanic did not eliminate the possibility of a GSS or solenoid contracts causing this , he did say it's extremely unlikely that only cold weather would affect that and if either one or the other issue was the problem it would have some symptoms manifestation during warm weather as well ..which it does not . Whereas a weakened battery does act up with a slow crank symptom when it's colder outside .


Checked the other batteries ; the one with the lowest reading was at 12.43 , followed by 12.87 , followed by 12.90 , followed by 13.11 and the other 968 at 13.27 . But the last two have been on a trickle charger so maybe not a good comparison ..so let's say just 12.4 to 12.9 compared to the one in question at 12.01

Also, all the other batteries are at least a couple of years , but I have no idea how much CCA any of them have , though I can't imagine it's more than the Interstate in the 968 which at least size-wise is the largest of all of them.

So maybe the slow crank is caused by a low charge or maybe it's something else , but it does look like there is a problem with the voltage regulator or the alternator , regardless ..

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[flash]

yeah - if it walks like a duck, and talks like a duck, odds are it's not a barcalounger

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[ds968]

Just had the car up on the hoist ( unrelated exhaust system work ..) and while there noticed that the starter motor is brand new . Does not even seem to be a rebuilt unit, this thing looks as it just came out of the box. I guess the engine rebuilder added a new starter in the mix, among other things . ( damn, why couldn't he put in an alternator also ?! ). So pretty sure we can eliminate the starter , very unlikely a new unit would act up , solenoid or gummy stuff , and be the cause of slow cranking when cold .

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[ds968]

OT , but on the battery topic ..the battery in a 2014 Jeep Grand Cherokee is located inside a deep " cubby " under the front passenger seat . All you have to do in order to replace that battery is move the seat , lift the carpet flap covering the cubby and there you go , easy as can be. But wait ! ...that's all fine and dandy , unless you need to replace the battery because it's dead as a door nail ; the seats only function via switches when you have electrical power , and there is no manual back and forth movement override ! Oops !

Lol, sure , there are battery " terminals " connections inside the engine compartment , so you can have the car jumped and then move the seat...that is , as long as the power door locks open so you can get in the car and release the hood . :-) :-). Gotta love new car engineering ideas .

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[MCL968]

Interesting about the Jeep.

 

First off, yours would not be the first (or even the 10th) new part that I have seen fail, so don't assume the starter is OK just because it's new.

 

Second, I would like to see what happens if you jump it with a good battery when it's cold and most likely to crank slowly. That might give you a better idea what the problem is.

 

Finally, I wonder about the impact a frayed trigger wire would have on your issue, If the wire is unable to send a full power signal from the ignition switch to the solenoid, it could impact the electromagnetic switch that is the solenoid, and not give it enough juice to fully engage. This would be easy to test by jumping the solenoid when the engine is cold to see if it cranks over fast or slow. It's a longshot, but in theory it could be affecting the clamping force of the solenoid.

 

Just some random thoughts in case the alternator is not the culprit.

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[ds968]

I could either put a trickle charger on it overnight , or, use jumper cables witn another car's battery to start it first thing in the morning ..it will be cooler this weekend so we might have a night with sub-60 temps .. Which one of the two start options would be better ?


As for the frayed trigger wire possibility , how do I bypass the solenoid ?


Yeah, not saying it's impossible for a new starter to be defective , just extremely unlikely . For that matter, even the battery could be a bad one in the bunch .

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[MCL968]

A simple check would be to locate the connector on the firewall that powers the solenoid when you start the car (and the alternator when the car is running), and run a jumper from the connector to the solenoid to see if the original wire is toast. As I said, I replaced both those wires with heavier gauge ones and I ran them in separate looms from the heavy power cable that drives the starter. As I understand it, if that trigger wire for the solenoid shorts out against the battery cable, the starter engages and if you left it in gear, the car drives off without you.

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[flash]

lol - that is how dan understands it as well (so do his garbage cans)

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[ds968]

Yup, good memory Flash ! For the benefit of others who have not seen the very , very old post on the topic - my six speed 968, which I left in gear when parked overnight in the garage , decided it would start on its own all of a sudden and lunge into the recyclables containers propped against the wall ( which was a blessing in disguise , because without those the car would have made contact with concrete ) . That's when I almost started believing in ghosts .

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[Rap]

Forget ghosts how about God? Lol

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[ds968]

That's a distinct possibility ; God does live in my garage so he could have started the car , probably trying to take it for a joy ride.

Eh, my fault really, he showed up at the door one evening and said : " hey buddy, can you put me up for the night ? " The dude never learns , look what happened the last time he said that very same thing to a few Romans . Ok, now that's way OT, maybe we should move God to tne Religulous thread , and leave this one for slow cranking diagnosis ..

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[ds968]

No slow cranking for the last couple of days, but night time temps just haven't been cold enough .


Installing the new voltage regulator on Tuesday or Thursday so it'll be interesting to see if the battery voltage reading changes from its consistent 12.01 V pre-crank level , or not .

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[az968]

Since you have two 968s is it worth the trouble to swap parts between the two and see if the problem moves? Things like batteries, ground cables aren't hard to move around.

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[ds968]

Still a bit too much hassle to do that . Especially if I need to crawl under the cars to do anything . I have a portable battery charger so there is no need to switch batteries , I'll just use that to see if an extra 0.7 V ( the portable charger reads 12.7 V ) makes any difference to the cranking speed , but I still have to wait until we have a cold night and morning to test that .

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[ds968]

Had the voltage regulator replaced today . The system was tested afterwards and it's performing at peak output , so after driving for the next couple of days I'll see if the battery holds more charge than the 12.01 reading it has had , when cold. If still low, I'll take back to Interstate for an exchange, considering it's only a few months old. I'll also have to see if that ringing noise coming from the alternator in the morning persists or if it might have been the regulator's worn brushes . Not to say tne starter is completely speared from suspicion , so if after all this and with a properly charged battery it still slow-cranks on cold mornings, I guess that's the next part replacement on the agenda ..

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[ds968]

Battery still reads between 11.95 and 12.01 when cold.   On cranking it drops as low as 8.5 - 9.0 for a fraction of a second and then right up to 13.5 - 13.7  when the engine is running. ( This is on the external voltmeter reading ) . 

So I called Interstate to prepare a new battery for exchange .  I told them what the problem is and they said this :  the battery ( group MPT 91 ) should never read more than 12 V when cold because that is its FULLY CHARGED level.

So anything between 11.75 and up to 12 is perfectly fine.   However, they do agree that 8.5 - 9.0 on cranking is a little low, so it could have a weak cell .  When I take it there they can also check the amps - this battery is rated at 700 CCA,

and they said that's what really counts on cranking output, the voltage level is not really as big of an issue .       

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[MCL968]

Yes on all accounts, CCA is what counts, and you probably do have a shorted cell.

 

Did the ringing sound in the alternator disappear? I suspect that the gremlin that was making the noise in your muffler simply relocated to the alternator when he (all shop gremlins are male, by the way) heard you were changing the exhaust system.

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[Bulti]

Still a bit weird. All of the 12V car batteries I know read about 12.5V when healthy and fully charged. Maybe even a bit more. When they drop close to 12, it's trickle charger time.


In any case, amps are indeed most important when cranking.

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