Occasional non-starter

[d1mkaz]

Maybe someone can put me in the right direction. Usually car starts without any issues, once it was parked in the garage for a while and when I tried to start - all usual lights on the dash came up but engine would not turn, I thought it's battery and connected a jump starter, but weirdly it did the same - lights on but no engine turn. After about 5 min and few dozens key turns it started and this issue never repeated for few weeks until today. I started up in the afternoon today without any problems and then had to drive in the evening and it did the same - turn key and only dash lights come up but engine does not turn. Opened the boot and checked fuses, wobbled relays and wires but could not fire it up. Definitely not the battery as after some time when I did not have any hope it just started up, so went where I needed to go and came back without stopping the engine, now parked near home and stopped and started as usual without any problems, waited few minutes and again no problems with starting up. Is that a starter motor failing? Any advise on how to check this?

[Brianmoooore]

You haven't said what engine or age, but I'll assume post facelift.
Take the cover off of the diagnostic socket and carefully identify and mark pins 11 an 14. The next time it won't start, leave the ignition on, make sure it's out of gear, and use a short piece of wire to link these two pins together. Does this activate the starter?

PS. You'll find fuses and relays etc., under the bonnet at the front end. None in the boot.

[d1mkaz]

You haven't said what engine or age, but I'll assume post facelift.
Take the cover off of the diagnostic socket and carefully identify and mark pins 11 an 14. The next time it won't start, leave the ignition on, make sure it's out of gear, and use a short piece of wire to link these two pins together. Does this activate the starter?

PS. You'll find fuses and relays etc., under the bonnet at the front end. None in the boot.

Thank you Brianmoooore, I meant under the bonnet, my bad English here, will try what you suggested.
It's E30 1989 320i convertable.

[d1mkaz]

You haven't said what engine or age, but I'll assume post facelift.
Take the cover off of the diagnostic socket and carefully identify and mark pins 11 an 14. The next time it won't start, leave the ignition on, make sure it's out of gear, and use a short piece of wire to link these two pins together. Does this activate the starter?

PS. You'll find fuses and relays etc., under the bonnet at the front end. None in the boot.

I made a picture of diagnostic socket just to confirm pins, can't find 14 but looking in net I think the ones that I pointed are 11 and 14. Is that correct? Thank you in advance.

IMG_1885.jpg

[Satan]

Think you have the correct ones there,

Screenshot 2020-11-14 at 13.01.03.jpg

[Brianmoooore]

That's the correct pins. Everyone should mark around the outside of them with paint or tipex for future reference.
Satan's chart is for a later BMW, with no connection to pin 11.

[d1mkaz]

That's the correct pins. Everyone should mark around the outside of them with paint or tipex for future reference.
Satan's chart is for a later BMW, with no connection to pin 11.

Thank you!

[Tzantushka]

Thank you!

Question, what transmission do you have in your car?

[d1mkaz]

Thank you!

Question, what transmission do you have in your car?

It's manual, why you're asking?

[Brianmoooore]

Because with an auto there's a well known possible cause of what you're experiencing, but it's always best to stick to a logical fault finding program, eliminating sections of the circuitry as you go, rather than making random guesses, however likely they are. This way, you DEFINITELY solve the problem, rather than maybe solve it, only for it to strike again at some very inconvenient moment in the future.

[MunsterScot]

Not wanting to hijack the thread.

I have a similar issue with a 1991 325i Auto. Sometimes the starter kicks on but engine will not start. I initially though is could have been the OBC as it can act as an immobiliser on the green wire from the ignition switch to the coil. Checked that and it's linked out. Then thought it could be the ignition stitch sometimes being faulty and not supplying power to the coil. So I've wired in a temporary wire and switch between the battery and the coil so the next time it doesn't start I can connect power direct to the coil and see what happens (ruling out the ignition switch or not).

Brianmoooore: What is the common well known possible cause of what I'm experiencing so I can check it out? Would it be related to the switch for detecting the car is in either 'P' or 'N'. But I thought if it was that the starter wouldn't turn.

Thanks.

[boiliebasher]

Also interested in the above question too. My 325i was originally auto converted to manual and I'm intrigued to see if bridging pins 11 and 14 in an auto will still force the starter motor to engage.....

[Brianmoooore]

Not wanting to hijack the thread.

I have a similar issue with a 1991 325i Auto. Sometimes the starter kicks on but engine will not start. I initially though is could have been the OBC as it can act as an immobiliser on the green wire from the ignition switch to the coil. Checked that and it's linked out. Then thought it could be the ignition stitch sometimes being faulty and not supplying power to the coil. So I've wired in a temporary wire and switch between the battery and the coil so the next time it doesn't start I can connect power direct to the coil and see what happens (ruling out the ignition switch or not).

Brianmoooore: What is the common well known possible cause of what I'm experiencing so I can check it out? Would it be related to the switch for detecting the car is in either 'P' or 'N'. But I thought if it was that the starter wouldn't turn.

Thanks.

Wire a small 12 volt lamp or LED between the coil + terminal and body earth with long enough wires to bring it into the cabin or poking through the back of the bonnet, so that it can be seen from inside the car.
The 'common fault' relates to the starter motor not operating, and is caused by the inhibitor switch not lining up when the car is in N or P. Usually caused by failed engine and/or gearbox mounts moving the gearbox from its correct position.

[Brianmoooore]

Also interested in the above question too. My 325i was originally auto converted to manual and I'm intrigued to see if bridging pins 11 and 14 in an auto will still force the starter motor to engage.....

11 and 14 linked work on all E30s, and doesn't require the ignition to be on to engage the starter, although the engine won't start if it isn't, of course.

[boiliebasher]

Also interested in the above question too. My 325i was originally auto converted to manual and I'm intrigued to see if bridging pins 11 and 14 in an auto will still force the starter motor to engage.....

11 and 14 linked work on all E30s, and doesn't require the ignition to be on to engage the starter, although the engine won't start if it isn't, of course.

Thanks for that. So essentially pins 11 and 14 would by pass the autobox PDNR safety switch? If so that's so handy to know

[boiliebasher]

So hypothetically speaking, if the ignition is on, but the auto box selected is in gear, say D, and you bridge 11 and 14 would it start and shunt the car forward the same as what it would if you try to start a manual car in gear?!

[Brianmoooore]

The only difference between doing this with a manual car rather than an auto, is a manual left in low gear would jump forward, even if the handbrake was on, but with an auto, the handbrake will hold at tickover revs., although you might be pushing your luck if the car is cold, and idles at the increased cold start revs.

[d1mkaz]

You haven't said what engine or age, but I'll assume post facelift.
Take the cover off of the diagnostic socket and carefully identify and mark pins 11 an 14. The next time it won't start, leave the ignition on, make sure it's out of gear, and use a short piece of wire to link these two pins together. Does this activate the starter?

PS. You'll find fuses and relays etc., under the bonnet at the front end. None in the boot.

So finally same issue came up. Luckily I was prepared and linking pins 11 an 14 worked, it fired up straight away. Just to mention, I have touch key immobiliser since 2005, never been an issue and it seems working - red light flushing when engaged and stops when disengaged. So I guess I need to check all wiring downstream of ignition lock.

Thank you!

[paultv]

I had a similar issue some years ago with a random start failure...turned out to be a severely worn ignition switch unit that clips to the base of the ignition barrel.

The barrel has a flat "lolly stick" paddle that protrudes into the centre of the switch section itself...the socket is nylon and the paddle is metal....eventually the nylon becomes so worn that the switch fails to rotate sufficiently to engage the start connection...and the result is a random failure. Also the clips that hold the switch unit to the barrel fail...this also causes a physical failure when you turn the key.

I remember that the car would start fine and then fail on odd occasions...but it eventually got worse.

Just a thought.

Paul

[d1mkaz]

Sorted few months ago, just a late update...

I was going to disconnect the immobiliser first and then replace quite pricey ignition switch unit. I never took the car out of the garage in winter so the battery was left disconnected. When I was starting it up it would only start linking pins 11 and 14 and although it was cranking it felt that the battery had not enough charge so I decided to replace it. The old battery was kind of small and had only 620 CCA, so I went for a bigger one with 680 CCA. Since battery replacement I never had a non-starting problem. I was waiting for it to happen again but now driving 2-3 times a week for a last couple months it starts every time without any issues. I still want to check the electric looms when winter comes.

Thanks everyone for advice. I don't participate much on the forum, but it's great to know that you can always find help here. I hope someone will find answers to their issues in my topics.