Starting Probelms

[170sport]

Hi, got a 1991 325i and it just will not start! When I say start I mean crank.

Basically drove it home about 2 weeks ago not a problem, no indication of any problems either. Left for acouple of days as normal then got in and went to start it and, all I could hear was a rapid clicking from the starter solinoid, so thought ahh no drama just a dead battery.

So took battery off and charged it up, still no joy, just a rapid clicking, so thought perhaps the amps in the battery are shot so bought a brand new battery chucked that on and still the same, just a rapid clicking from the Solinoid. Moved on and bought a new starter motor, chucked that on and still the same just a rapid clicking. Swapped over some of the 'load relays K5 and K7 I think' like for like and still the same, bridged pins 11 and 14 on the diagnostic plug as per the wiki and still the same.

Changed the main relay, albeit for a second hand one and still the same, checked all connections, earths, alternator, and obvious signs of any chaffing etc, all seem ok. Even got a spanner on the crank and turned it over just incase the whole engine had siezed but she spins lovely. Basically it's been perfectly OK never had any problems then just one morning this happens..

Does anyone know the 'electrical route' in what happens electrically when wanting to start the engine? So possibly I could start at the first point and work my way through checking and testing all the components maybe?

Any help?

Thank you.

[Brianmoooore]

If you get no joy from bridging 11 and 14, then it is a connection problem with the circuit made up of the battery, the big battery wires, the starter motor, the body to engine earth strap, the joints between the starter motor and block, and the joint between the alloy engine mount and block.
I only posted last week how I have never come across a case of the latter on an E30, but it's a distinct possibility here.
I see that we are talking about a 325. If this is a saloon, then the battery should be in the boot, so that gives another possible place for the problem to be - the phantom battery + terminal on the RH side of the engine bulkhead.
As a first test, connect a 12 volt bulb between the earth terminal on top of the RH front suspension turret and a clean nut or bolt on top of the engine, and see if it lights when you start to crank the car.

[170sport]

Yeah could try earth strap? Really engine mounts? I'll nip round with the rachett and check tho. The starter does turn as I can see the fan turning but only like a quarter revolution but it just doesn't stay engaged. Almost like something is telling the starter solinoid to engage and disengage constantly. Do they have just one earth strap off the sump to the chassis leg? Or is there typically more elsewhere?

The battery is up front under the bonnet, and perhaps I'm reading it wrong but if I connect a 12v lamp between the RH turret and a clean part on the engine then surely it won't light up because it's earth and Earth?

Just done another few tests:

With everything connected as it should be the starter solinoid just rapidly clicks.

Carefully I isolated the big supply cable off the back of the starter and then engaged the ignition and the solinoid engages, locks and remains engaged until I release the key, (no rapid clicking) then when I reconnect the main supply to the back of the starter it's back to square one again?

[Brianmoooore]

if I connect a 12v lamp between the RH turret and a clean part on the engine then surely it won't light up because it's earth and Earth?

That's the point! If the lamp lights, then you know where the 12 volts that should be turning your starter is going.
Forget the engine mount to engine joint - that applies to certain other BMW engines - the M20 E30 earth strap is from the sump, as you say.
Note that if the earth strap is faulty or disconnected, and you try to crank the engine, the engine loom will be seriously damaged by one of the wires from the oil level sensor becoming red hot, as a result of a design fault by BMW.

[170sport]

Ok I appreciate what you're saying about the lamp it makes sense for the voltage side of things but it then worries me where the battery is unloading it's 680 odd amps too.. Cuz if the starter isn't using them then what is??

I'm going to run some more checks tomorrow, from what you guys suggest, what makes it irritating is that it happened over a course of it being stationary. I don't understand how when disconnecting the starter main power cable from the starter motor, the solinoid engages as it should and remains until you release the key yet when it's connected like its suppose to be, it just rapidly clicks... But anyway, going to start some checks tomorrow and start from scratch like you suggest.

Thanks for your help.

[Brianmoooore]

The 680 odd amps aren't being 'unloaded'. They are being stopped by a very small resistance that shouldn't be there. With the motor itself disconnected, there's enough amps getting through to work the solenoid.
This is what causes the clicking sound when the wires are put back on. There's enough power to pull in the solenoid, but when that happens, the motor is connected, which immediately takes all the power available, leaving insufficient for the solenoid, which promptly releases and disconnects the motor. This releases enough power to pull in the solenoid again, so the cycle repeats until the key is released.

[170sport]

The solinoid takes its power remotely, it doesn't come off the main cables. I understand what you're saying tho, when the motor demands all the power to turn there's possibly not enough left in the battery to maintain the engagement of the solinoid, so it disconnects thus breaking the circuit to the motor, power is then readily available again so the solinoid re-engages and so the cycle repeats. So instantly that would suggest faulty battery at the easiest not providing enough power but I've changed that for a brand new one, even put the new battery on my van to see if it starts that thinking its a duff new battery and it starts ok, I've been round and checked everything for tightness and it still won't start. Unless water has got in some where shorting something across I don't know?

What about ecu?

[Brianmoooore]

Water getting in would have no effect. The engine would crank if the car was at the bottom of a river, right up to the point that the first cylinder filled with water. It's a common fallacy that water conducts electricity.
Have you tried the 12 volt bulb test yet?

[170sport]

Water also creates corrosion!

Forget it, I'll go somewhere else where there's less attitude from senior members.

[fixedwheelnut]

Brian is one of the most helpful people on here, I don't read any attitude in his comments, he has simply asked if you have carried out the 12v test light test yet, once we know the answer to that it narrows down the options of what the fault can be,

I would have asked the same questions;
Option 1/ the starter is not turning because it isn't getting a full 12 volts so a break or high resistance in the positive connection

Option 2/ The starter itself is faulty

Option 3/ the earth connection of the starter or engine itself are faulty.

My money would be a broken earth cable at the sump to body connection front left of the engine.

[aze30]

Water also creates corrosion!

Forget it, I'll go somewhere else where there's less attitude from senior members.

i dont see any attitude mate...brian is being helpful...

[Brianmoooore]

Had a look back at this clown's previous 'contributions' to the zone. Turns out he had another marathon (two full pages) thread, wasting our time, going round in circles, on exactly the same subject (engine won't crank) three and a half years ago! That didn't reach any conclusions either.

[Gert_8]

This fella perfectly fits the description of an askhole...

Yep! I've been following the thread, just out of interest and to see if I can learn something. Certainly an askhole!

[aimlessrock]

Brain has been his usual helpful self and tried to help a zoner out.

BTW Brian i meant to tell you that i got to the bottom of my ABS fault a couple of months ago, I went over the tests and found nothing out of the ordinary. i drove the car about 100 yards turned it off (back on the garage) and the abs light has been fine since. By fine i mean it light up of start up then goes off.

Could it have just needed a rest and to get a feed from the sensors?..this is the only answer i could come up with..

[bosers]

What a helmet. Love your work, Mr Mooooooore.