RealOEM :) I hope it isnt an in-tank pump!

What are the other symptoms you have? Might help narrow it down.

Yes, I miss those cars, they are nice :)

thanks for reply, glow plugs at 7C temp I have been informed dont kick in at that temp....could be bad fuel or the actual fuel pump or fuel pump relay....or even a crappy battery that whilst showing is ok with regards to volts has crappy CCA?

Symptoms temps dropped and turning over has got laboured....temps go up its fine again....don't ban me for showing a merc on the site...wish I had it but the rust was too severe and I seized up the engine....RIP 1973-2007

Nice W115! Mods, sorry, don't ban us please lol!

So on cold temps turning over is laboured...meaning the starter spins the engine slower during cold temps? Is it slower from the moment you turn the key or does it start spinning normally initially and then begin to spin slower and slower?

Regarding glow plugs, I personally doubt they would only turn on at the temperature. I got curious so I googled a bit and found some conflicting info:


"Quote from WDS:

Preheating System DDE 4.0

The voltage for the preheater plugs is supplied via the preheater relay. The relay is switched by the DDE control unit.
The heater plugs are designed as sheathed-element glow plugs.

Preheater time control
The preheating duration is dependent on the engine coolant temperature and battery voltage and is indicated by the preheating/DDE indicator.

Preheating
At temperatures below 5 °C, preheating takes place for at least 4 seconds. The preheating time increases as the temperature decreases.

After-heating
After-heating takes place after engine start at temperatures below 20 °C in order to improve idle and exhaust characteristics.

Start preheating
Start preheating takes place for approx. 10 seconds if after the preheating time has elapsed the engine is not started and the ignition remain on.

Troubleshooting
The DDE control unit itself detects a short/break in relay activation (type of fault "activation short-circuit ..." or "activation break ..."). The DDE control unit receives a fault signal from the preheater relay in the form of the S_GRS signal if there is a fault in the preheater plugs, preheater relay or in the voltage supply of the relay (type of fault "preheater system fault"). Fault code 3505 "Preheating system" is stored in both cases.


Combustion preheating system DDE 5.0/6.0

The glowplug system consists of the following components:
• DDE control unit
• electronic glowplug control unit
• quick-start glowplugs
• Bit serial data interface (BSD) and electrical leads
A heater plug relay as in the case of DDE 4.0 is not fitted.
The quick-start glowplugs are designed for a voltage of between 5.3 and 7.8 Volts. In the initial heating stage, system voltage may also be applied for a short time.
The essential differences from the glowplug systems on previous models are as follows:
• control of the glowplugs is by pulse width modulation
• the glowplug relay has been dispensed with and its function taken over by electronic output stages on the glowplug control unit
• an emergency glowplug function has been introduced
• quick-start glowplugs have been introduced
• each of the four glowplug circuits can be diagnosed individually
To check the glow system, there are two adapter leads:
• 1-pin, order number 13 6 470
• 12-pin, order number 13 6 460
in conjunction with 26-pin measurement box, order number 61 1 459

Function
The glowplug control unit communicates with the DDE control unit via the bit serial data interface.
The required heating output is determined by the DDE control unit on the basis of the following operational parameters:
• Coolant temperature
• Vehicle voltage
Two other operational parameters determine the point at which glowplug function is activated and deactivated:
• Engine speed
• Injection volume
The DDE control unit transmits the heating request to the glowplug control unit via the bit serial data interface. The glowplug control unit puts the request into effect by activating the glowplugs by means of a pulse-width modulated signal. In addition, the glowplug control unit sends diagnostic and status information back to the DDE control unit.

Preheating
At coolant temperatures below 25°C, there is a preheating period of 0.5 seconds. The preheating period increases as the temperature falls, reaching a maximum of 2.7 seconds at a coolant temperature of less than -25°C.
Activation of the glowplug system on the instrument cluster only occurs at coolant temperatures below 0°C.

After-heating
At coolant temperatures below 30°C, there is a temperature-dependent after-heating period to improve idling and exhaust emission characteristics.
Start preheating
Start preheating takes place for approx. 10 seconds if after the preheating time has elapsed the engine is not started and the ignition remain on.

Troubleshooting
The DDE control unit monitors communication with the glowplug control unit. In the event of a fault on the bit serial data interface, the DDE control unit stores the following fault code:
• 4203, Glowplug control unit, no communication via bit serial data interface
The glowplug control unit monitors activation of the individual glowplugs and is able to detect the following faults and store them for each glowplug:
• Short circuit to earth
• Break
• Excess temperature output stage
If the glowplug control unit detects a fault, it reports it to the DDE control unit which stores the fault in its fault memory."

https://www.bmwland.co.uk/forums/vie...6&f=17&t=81186

Hey thanks for reply......havent noticed which of below applies, one thing that is driving me nuts is that this a.m it was 5.5C and the X5 started fine....
wondering if it could be the fuel pump relay as some say...

re " So on cold temps turning over is laboured...meaning the starter spins the engine slower during cold temps? Is it slower from the moment you turn the key or does it start spinning normally initially and then begin to spin slower and slower?"

cold start problem with fully charged battery
 

Had exactly the same 3 weeks ago. My diesel injectors were worn out. Bosch service has hooked up the diag computer and showed me that 4 of the 6 injectors had a bad rail pressure. Now they have repaired them and she starts like a world champion. Prize: EUR 1600.- BMW would replace them for 3x that prize.

I have a 2002 3.0d with 183.000 km.
Glow plugs will throw an error. Had that some years ago.


LG Helmuth

Helmuth thanks for the reply....jeez that is a big bill .....was it a difficult job?

as for hearing the fuel pump, yup did manage to here a whirring noise in rear so that seems ok.....but again relay maybe intermittent..... gonna start with battery AGAIN (despite stating in post that I had this issue witha full battery)...and as I dont have a load tester will do this:

fully charge battery out of car take reading 12.8-12.6 v should be the reading
then check after a couple of minutes should be 12.7-12.6
then check after 6 hours should be no lower than 12.6 IF it is lower, then battery needs to go...and I can take it from there....

cold start problem with fully charged battery
 

I would have somebody to check the error memory of the car and also to check online rail pressure values. The tech from Bosch service told me after some minutes what's wrong. The bill for having that checked is low. Then you can decide.

About the difficulty of the job: they had to remove the injectors and put them on a test stand. There they found out that 4 of the 6 were not in the proper value any more. Then they ordered repair sets and fixed all of them. Working time was about 8 hours. The rest was material.

LG Helmuth

thanks Helmuth...regarding cranking volts I got following off an e38 site, does it apply to the x5 too? anything lower than 9v whilst cranking means batt is rubbish?


TEST-NR. 09
VB: xx.x V (battery voltage)

Useful for battery condition tests. Engine not running value should be above 12V....cranking voltage should not drop below 9V. When fully charged the voltage should show > 14V

Omodos, I second Helmuth's suggestion on getting the codes pulled. Hopefully you will gets some leads there.

Its approx. 9.6v but you will need a voltmeter with MIN/MAX function to register the cranking voltage.Its the cranking that takes the most load on a battery.On cranking ,even a new battery will register below 10v but it will recover immediately to 12 v+ ,as you will see ,when your turn the engine off again.
I am glad my X5 doesnt have START/STOP function as this takes a toll on any battery and our customers that do short trips regularly complain of battery problems .I have it on my Alfa ,but its always switched off :)