There are a series of reported starter issues with our cars, and I will try to address them all here in a single post for ease of reference.
First thing to say is that 90% of all starting issues are directly related to the battery. These cars need a full charge on a strong, fresh battery to start.
Common symptoms.
A click when you press the starter button. (sometimes starts on second try).
Common causes and solutions in the order you should try them.
1.) Hold the starter button down for at least 3 seconds, and be sure your clutch pedal is fully depressed.
2.) Recharge and check your battery is holding its charge, and giving full power. It has been often noted that the battery does not keep its charge in the Z8 due to the constant drain that is part of the Z8's electrical systems, even when the car is off, and the flimsy BMW charger cannot keep up with the rate of discharge.
3.) Make sure your key is charged, leave it in the ignition in the off position overnight, with battery on trickle charge.
4.) Replace battery. The Z8 Club recommends BMW's new style AGM-batteries (Absorbent Glass Mat-battery). There are many, many instances of fully charged batteries failing to start the car, then a fresh battery is installed, and all is good.
5.) Check and replace the starter motor. Several have been replaced both here in the US and with the Club in the EU, however this starter has been used for a number of years on many other BMW's with no indication of a problem. The starter motor is common to both the Z8 & the Alpina. (Bosch PMGR 1.7kW/12 Volt, CW, 9-Tooth Pinion). The solenoid does seem to be part of the problem, but it is an integral part of the starter, and can only be replaced with it.
The BMW OE part # is 12-41-1-468-622, 12-41-1-729-981.
NB: Out of all the owners here and in the Z8 Club only one had a problem with the actual starter button. Similar symptoms to a flat battery, but only changing the switch solved the starting problem.
Also two Z8 Club members in Europe and two of our board members here have had problems with the ignition lock. This can disable the car completely, and require return to the dealer to replace the unit.
Harvey2 posted this info on the cars starting system in one of the other threads.
I've been digging through some documentation. Here is some info from BMW.
There are several ?relays? or electronic functions that must be satisfied or ?good? before the starter motor will receive power after the start button is pressed.
- Electronic Immobilizer Control Unit (EWS)
- Start relay (not the one in the starter motor assembly)
- DME control unit
- Fuse 21 supplying the start button switch
- Fuse 107 supplying the EWS
- The relay built inside the starter assembly (this relay has two coils with separate inputs)
A discussion of the Vehicle Immobilization System is the place to start to understand the start sequence. For interest, and not really on topic, but anyways, here are some key points about the Vehicle Immobilisation System (as read from BMW literature pertaining to the Z8)
- the key does not require an internal battery to start the car. There is a transponder chip inside the key that is powered by magnetic field coupling from the ring coil in the ignition key slot. While not explicitly mentioned, this is obviously separate from the wireless remote functions in the key as those obviously need a battery to function.
- A fault in communication between key transponder and EWS3 control unit would be logged in the fault code memory, separate fault logging for each key.
- Don?t lose too many keys, as the control unit can only handle a maximum of 10 key codes, or 6 replacement keys.
Ok, so let?s look at how the car starts. First you insert your key. The key communicates with the EWS3.3 control unit. When it satisfies the EWS by sending data for identification and start enable, the EWS releases (enables) the starter relay located in the control unit and also sends a coded enable via datalink to the DME. This enable has to be communicated successfully for the car to start as the DME is responsible to enable the fuel supply and ignition functions. After the engine starts, sends a code change into the key and a new code is also stored in the DME.
Both the EWS and the DME maintain identical tables of codes. These codes are changed every time you try to start your car. Engine start is allowed only if the code sent by the EWS agrees with the code in the DME. Since the codes of the DME and EWS are matched in production of the car, you can?t do swapping of one or the other of these units for test purposes. If faults cause the codes to not match anymore, it is possible for BMW service to rematch the codes.
EWS3 is used on various BMWs and I note that automatic transmissions also have an enable switch if the selector is in P or N which must be satisfied for the car to start. This may apply to Alpinas. Interestingly the EWS gets this signal along two paths, one via K Bus and the other via data link. If one or the other is not received, noticeable start delays ranging up to 2 seconds might occur, but then again, this only applies to automatics.
If a new key is used for the very first time, there is a delay of up to 2 seconds before start.
Below is a diagram showing the electrical connections enabling the starter. With this kind of information, and the help of a BMW tech to find the various points, it is possible to put a multichannel recording device to show which nodes receive voltage and which do not upon a failed start sequence (the infamous "click" but no start). That seems like the most effective way to find where this problem is occurring. But it implies that the logging device is attached and left on a car for a long period in hopes that the fault will occur. I wonder if this capability is actually built in to the car already.
edit: the fact that we hear a click indicates that an electromechanical relay or solenoid is being powered on the press of the button. There are only two that I can see for sure, one is the "start relay" and the other is the relay in the starter motor assembly. It isn't clear if there is one on the EWS also, but yes I think there might be. The "start relay" is a small white relay located at the right rear of the engine compartment under a cover located beside the DME box, which is high up just under the hood and ahead of the firewall.
The attachment is a simplified diagram showing how power gets to the starter motor. I admit to being a bit puzzled about the configuration of the two solenoids in the starter. I copied this directly from the symbol used in the BMW document. Of the two solenoids, the one on the left of the diagram clearly operates the relay contacts, but the one on the right is a bit unusual.
Thanks Harvey2 for the great info.