Intermittent slow starts

M

mjennings23

Senior member
 North West
So I've noticed the past week, my car seems to sometimes be hesitant to start in the morning, as if it's struggling to crank.

Now the odd bits. First off it's seemingly random, this morning it made hardly any attempt to turn over the first turn of the key, so I tried again and it fired up instantly with no bother. Similar story a few days back.

It's had a new alternator 2 years ago and a new starter a few months ago. Battery is around 4 years old so I'd expect it to still be fine, but surely a bad battery wouldn't cause it to hesitate first but then start fine?

I can't see it being fuel related as when it doesn't start up, the engine isn't turning over at all.

Any ideas? Do I have a bit of a dud starter?
 
I'd check the battery voltage first thing and eliminate the battery/charging before moving on, It's also worth checking that the earth connections are all clean and tight.

The basic DIY test of battery & alternator is with a volt meter over the battery +/- terminals without the engine running you are looking for at least 12.4 Volts on a good battery. Re the alternator, test with the engine running and electrical accessories OFF. A healthy alternator should be giving around 13.7v - 14.5v. Turn on a load of accessories then see if the voltage drops below 13V, if so the alternator is functioning but marginal and may be on it's way out.

Then I'd be suspecting the ignition key switch which seems to be a common fault and causes random intermittent starting problems. Loads of threads on here if you search https://z4-forum.com/forum/viewtopic.php?f=3&t=113381

Keep us updated :thumbsup:
 
Wouldn't have thought about the ignition switch, and reading the previous threads it certainly sounds likely. I note some websites say they can trigger weird electronics too, which I have noticed with my 12v socket seemingly randomly restarting when my phone is plugged in.

I'd pretty much ruled out battery as, even if it doesn't start the first time, the second attempt it kicks in instantly and shows no sign of low power. Will check it with a multimeter as soon as I can mind.
 
Worth bearing in mind that even a brand new battery can be rendered completely and permanently knackered if it is left discharged (below 11V) for even a few days. The plates get sulphated and are not really recoverable. Does make me wonder how battery manufacturers can possibly offer any kind of guarantee (unless it is very limited to just manufacturing defects etc) when they are so vulnerable to user abuse.

I think battery or starter is more likely than ignition switch imho.
 
ph001 said:
Worth bearing in mind that even a brand new battery can be rendered completely and permanently knackered if it is left discharged (below 11V) for even a few days. The plates get sulphated and are not really recoverable. Does make me wonder how battery manufacturers can possibly offer any kind of guarantee (unless it is very limited to just manufacturing defects etc) when they are so vulnerable to user abuse.

I think battery or starter is more likely than ignition switch imho.
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Appreciate the input re batteries, but surely that doesn't make much sense when 9 times out of 10 it fires up instantly, then 1 out of 10 there's absolutely nothing. If the battery was going then surely it would struggle to start at all times?

The longest the car has been left sitting in my ownership is 1 week too, and it's always started instantly after sitting for that long.

It's had a new Bosch starter about 4 months ago too, so I'm ruling that out for now.
 
mjennings23 said:
ph001 said:
Worth bearing in mind that even a brand new battery can be rendered completely and permanently knackered if it is left discharged (below 11V) for even a few days. The plates get sulphated and are not really recoverable. Does make me wonder how battery manufacturers can possibly offer any kind of guarantee (unless it is very limited to just manufacturing defects etc) when they are so vulnerable to user abuse.

I think battery or starter is more likely than ignition switch imho.
Click to expand...

Appreciate the input re batteries, but surely that doesn't make much sense when 9 times out of 10 it fires up instantly, then 1 out of 10 there's absolutely nothing. If the battery was going then surely it would struggle to start at all times?

The longest the car has been left sitting in my ownership is 1 week too, and it's always started instantly after sitting for that long.

It's had a new Bosch starter about 4 months ago too, so I'm ruling that out for now.
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Maybe when the starter was fitted the cables weren’t tightened up correctly, that could cause an intermittent problem. :?
Rob
 
For sure, will have a look tonight. I'm pretty sure I tightened everything down plenty when changing it out mind.
 
mjennings23 said:
Appreciate the input re batteries, but surely that doesn't make much sense when 9 times out of 10 it fires up instantly, then 1 out of 10 there's absolutely nothing.
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I thought you said “reluctant to crank” in your original post. If it’s completely dead then that does change things.
 
ph001 said:
mjennings23 said:
Appreciate the input re batteries, but surely that doesn't make much sense when 9 times out of 10 it fires up instantly, then 1 out of 10 there's absolutely nothing.
Click to expand...


I thought you said “reluctant to crank” in your original post. If it’s completely dead then that does change things.
Click to expand...

Yeah, that wasn't worded great. All the electrics come on fine but when it doesnt work, turning the key gives nothing at all from the ignition. Alkl the in car electrics work fine still, but not a single noise from the starter or any indication of cranking. Then you try again, it cranks instantly and starts fine.
 
mjennings23 said:
ph001 said:
mjennings23 said:
Appreciate the input re batteries, but surely that doesn't make much sense when 9 times out of 10 it fires up instantly, then 1 out of 10 there's absolutely nothing.
Click to expand...


I thought you said “reluctant to crank” in your original post. If it’s completely dead then that does change things.
Click to expand...

Yeah, that wasn't worded great. All the electrics come on fine but when it doesnt work, turning the key gives nothing at all from the ignition. Alkl the in car electrics work fine still, but not a single noise from the starter or any indication of cranking. Then you try again, it cranks instantly and starts fine.
Click to expand...

The ignition barrels have been known to cause that issue i think? :?
Rob
 
Yeh its almost certainly one of those two! The way you would normally narrow that down is to get a piece of 2x2 and place it against the starter when it doesn’t crank. Then give it a tap with a hammer, usually that is enough to unstick the brushes and bring it to life. If that has no effect then probably the switch.
 
Well a replacement switch seems to have solved the issue, or at least it's not occured since!

As is typical though, I also managed to snap the bonnet release cable when doing an under the bonnet check i.e. fluids and levels. Mega :headbang: Suppose it is 15 years old mind, so can't be too annoyed at that.

Well they say bad luck comes in 3, what next? :rofl:
 
mjennings23 said:
Well a replacement switch seems to have solved the issue, or at least it's not occured since!

As is typical though, I also managed to snap the bonnet release cable when doing an under the bonnet check i.e. fluids and levels. Mega :headbang: Suppose it is 15 years old mind, so can't be too annoyed at that.

Well they say bad luck comes in 3, what next? :rofl:
Click to expand...

Glad it seems to have fixed it :thumbsup:
 
Happy to report it's running healthy now, and also the bonnet release cable is replaced and now doesn't feel like I'm going to rip the handle out trying to open it :rofl:
 
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