Intermittent starting issues

Invertigo · 10 Oct 2019 at 09:08

First things first, car is a 04 Z4.

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 cranking over at all, so signs point to something in the electrical circuit.

Any ideas? Do I have a bit of a dud starter?

paradigm · 10 Oct 2019 at 10:09

Could be the starter motor itself on the way out if it’s failing to turn over at all.

Have you tried the engineers tap when it has problems?

Maccy · 10 Oct 2019 at 10:52

Starter motor, MAF sensor (if it has one) or high pressure fuel pump. I've just gone through the same issues with my 911 (granted a different car, but very similar behaviour). Turned out to be the HPFP.

Invertigo · 10 Oct 2019 at 11:36

Starter motor is new, so can't see that being a likely culprit. No HPFP that I can see as it's a port injected engine.

Done some reading on owners clubs and it seems the ignition barrel switch can play up on this sort of age BMW, it's the cheapest option so looking at that first.

red eye · 10 Oct 2019 at 15:54

Invertigo said:
Starter motor is new, so can't see that being a likely culprit. No HPFP that I can see as it's a port injected engine.

Done some reading on owners clubs and it seems the ignition barrel switch can play up on this sort of age BMW, it's the cheapest option so looking at that first.

Before pulling out the parts cannon check the connections on the starter. As it’s new, holding the starter while getting a bolt in requires two hands if there’s no space you could use the power lead to hold the starter the nut could have been missed

Invertigo · 10 Oct 2019 at 16:29

red eye said:
Before pulling out the parts cannon check the connections on the starter. As it’s new, holding the starter while getting a bolt in requires two hands if there’s no space you could use the power lead to hold the starter the nut could have been missed

Will have a look at it this evening. When I say new I mean a few months ago with no issues prior to this week. Also it was fitted by myself and there certainly wasn't any parts left over!

Rroff · 10 Oct 2019 at 16:36

I'd check the battery voltages as a matter of course.

Also possible some of the wiring has deteriorated or corroded causing some resistance, etc. I assume as it sounds like it is struggling to even turn over it is unlikely to be spark plug related.

hominid · 10 Oct 2019 at 16:55

Another vote for battery, it's getting colder in the mornings now so any battery with a weak cell or two will struggle starting the car.

It could also be corrosion on the starter solenoid trigger wire, or the starter solenoid itself, so even if you turn the key nothing will happen(it can be intermittent).. Listen to the car for the solenoid tick when you try and start the car, if it ticks/clicks, then the solenoid/starter trigger wire is ok, if not have a look around that area and clean the terminals on the starter motor.

Lashout_UK · 10 Oct 2019 at 17:57

Had a battery with a duff cell do the very same thing.

red eye · 10 Oct 2019 at 18:50

Invertigo said:
Will have a look at it this evening. When I say new I mean a few months ago with no issues prior to this week. Also it was fitted by myself and there certainly wasn't any parts left over!

I ment the +12v feed 13mm nut and the feed for the soloniod 10mm nut / plug. If you nip these up properly you get intermittent starting issues

red eye · 10 Oct 2019 at 18:55

Lashout_UK said:
Had a battery with a duff cell do the very same thing.

Lose terminal could be the problem too since you have to disconnect the battery when changing anything with a 12v feed.

But unless you want to spend £50-120 on a drop tester your going to have to take it qwik **** or Halfords and get them to test it, your local garage might have one

Invertigo · 10 Oct 2019 at 19:44

I feel like I've probably worded the initial problem a bit wrong, now that I re-read it. Its not that the engine struggles to start, more so that it flat out doesnt even attempt to. Then when it does, it starts up instantly without any issues.

hominid · 11 Oct 2019 at 12:06

Invertigo said:
I feel like I've probably worded the initial problem a bit wrong, now that I re-read it. Its not that the engine struggles to start, more so that it flat out doesnt even attempt to. Then when it does, it starts up instantly without any issues.

That's why I mentioned this:

hominid said:
It could also be corrosion on the starter solenoid trigger wire, or the starter solenoid itself, so even if you turn the key nothing will happen(it can be intermittent).. Listen to the car for the solenoid tick when you try and start the car, if it ticks/clicks, then the solenoid/starter trigger wire is ok, if not have a look around that area and clean the terminals on the starter motor.

DXP55 · 11 Oct 2019 at 14:12

I had a intermittent starting problem a while back - wouldn't fire first go of key but went on next- Turned out to be lose clamps on battery. Funny enough next door had same issues and it was same thing - I tightened up battery terminal by at least two turns. Both our cars had been to the dealer for work which needed battery disconnecting.
The wife also had to call AA out as car wouldn't start - That was rusty earths. - Cars today seem to have a lot of earth points and what I found was they have a captive nut on back of a panel and earth is then screwed on without scraping paint off - so everything is relying on a clean bolt thread.

Mate over the road has put extra earth wires from battery to body and battery to starter and alternator -engine - he says his starts first time now. All these cars are diesel.