Poor cold starting 2.5DSE

Hi,

I've got a RR 2.5DSE (BMW) on a 98 plate.

I'm having trouble starting when it's cold, It turns over & fires up first time but I'm getting a bluey white smoke from the exhaust, also it feels like not all the cylinders are fireing when on tick over just after starting. it smokes like this for maybee 400yds then it's fine. If I stop & then fire it up again it's fine, unless I let the block totaly cool down, like overnight.

A friend of mine has used his "snap on" diagnostics which has given the error of "Glow Control 25". we have looked this up on "Autodata" software which does not list an error number "25"; it does however list error "49" giving a probable cause as: Wireing, Glow plugs or Glow plug control module! The glow plugs were replaced not that long ago, so what do you think?

Is the Glow Plug control module expensive? easy to replace? could it be somthing else?

your blue smoke would be oil that is burning away,as for the rough running a quick fuel filter change will probably help you no end if you havent already done so.

It's had new Oil & Fuel filters as well as a new lift pump (genuine parts).

The smoke is mainly white/grey with a hint of blue & it isnt using any oil.

you are still buring oil to get the smoke. some must be leaking to the exhaust somehow.if your getting white colour then that could be a coolant problem which could {god forbid} even lead to head gasket. does it run at the right temperture and gauge reading halfway once the stat has opened.

Temp gauge only reach's halfway in hot weather with air con on, at which point viscous fan kicks in. in this weather it never reach's half way. I've had this RR since 99 (10 months old) the temp gauge has always been same.

does the heater work and is there a thermostat in it. when stat opens your gauge should be halfway.

Heater works fine & there is a stat in it, which works fine, as it shows hotter on hot days & colder on days like this.

Just to add, with the diesel P38's its perfectly normal for the temp gauge to not reach half way on cold days - so I wouldn't worry about that.

It might be a good idea to have it hooked upto a proper diagnostic machine that is designed for the P38, like a Autologic/Rovacom and see what codes are logged. A generic OBDII scanner really isn't any good for these vehicles.

You 100% sure the smoke you get is blue at startup?? It has to be oil if it is yet you say you aren't using any??

-Wills

OK the smoke,

Got the wife to give her oppinion! she reckons theres no blue in it at all! she also reckons that it's not white but grey, albeit pale grey.

Spoke to a RR specialist, told him the story & how it only smokes in cold weather, he thinks it could be injector No4 that has the needle lift sensor, reckons if that's had it, it could be reason for smoke & poor running at cold start up, or even the glow plug control unit! But needs to put diagnostics on to see!

If it is #4 the cheapest you can get one from is German Swedish French (for the BMW engine) you need a special tool to take it out as well

have looked on the troubleshooter(snap-on modis)error 25 is glow plug or controller so i would suggest you have a knackered glow plug before you worry about injector no 4 check them it costs nothing to check if your doing it yourself ,take all wires off glow plugs test the plugs then make sure you have live at each cable when the glow plug light is on i would be highly surprised if all are ok as you are getting a glow control fault and that wont change no matter what scanner is reading the fault

It is very hard to take your blinkers off when looking at a fault. The code reader reported the glow plug control module so it is very very unlikely your engine is burning oil or that any injectors are faulty.
The more likely cause is that 1 or more cylinders are cold on start up. You get the equivalent of an over fuel situation. It runs as ruff as and the excess un burnt fuel burns off in the exhaust giving plumbs of smoke.

The glow plug control module is triggered by the engine ecu on Pin 8 which is a black and yellow wire.
Pin 8 Engine ECU is - with the longest row of pins on the bottom as you look at them. Count 8 from the right along the bottom.

The glow plug timer unit has an un fused battery supply which should be checked for battery voltage.

Check the voltage on black and yellow wire, if 0 volts then you have a circuit fault on the glow circuit.
If battery volts then you may have a coolant temp switch fault and the engine ecu doesn't think it is cold enough to put the glow plugs on or the engine ecu has an internal fault.

You can test the glow plug circuit by putting the black and yellow wire to earth. Do this with everything connected. This will trigger the glow plug timer and you can check that the glow plugs are receiving 12 volts and that it starts ok.

I have had many engine ecu's were the internal circuit for pin 8 fails so it will never trigger the glow plugs.
Most common issues are just temperature related.

Sorry Ian post overlaped slightly there.

injecters does seem logical captin

What is logical about the injectors until you have checked the glow plug circuit.
Glow plug control Fault isn't showing on the diagnostic kit for the fun of it.

change your glow plugs; mine was the same; all fixed now.

Was this resolved??

this is EXACTLY the same fault as mine. mine is defo diesel smoke and not oil though, it even smells like diesel. I'm going to recheck the glow plugs as I've done the spill pipes and the clear pipe from the filter. the car has 3/4 of a tank of diesel and a fully charged new battery. still takes ages to start. in fact its so bad I'm not using it.

Mtechuk, what should be on the black and yellow wire?

Sorry for the late reply. There should be 12 volts when the Engine ecu is not switching the glow plugs on and 0 Volts when the Ecu is switching the glow plugs on.

Occasionally if you have a poor earth from the Engine Ecu to chassis ground then the switched reading may be anywhere between 0 and say 6 volts, depending how bad the earth problem is.

You can remove the coolant temperature switch Plug to induce a coolant fault
This will force the Ecu to switch the Glow plugs on.

You can put the Black and yellow wire to ground yourself to override the Ecu control altogether.

I see what people mean about the Injectors. Yes leaking or faulty injectors do cause poor starting But the engine Ecu monitors for the Glow plug control unit switch. If the voltage is not present or the Engine Ecu cannot perform the switch then this fault is logged. Therefore if the fault remains
there is no need to look anywhere else until it is rectified

I'm sorry for Hi-jacking this thread. Mtechuck if I put a switch to ground from pin 8 would this do any damage? its not likely to damage anything else. I cant find the circuit on RAVE to check it myself.

Hi, no. No damage at all. I do the test myself all the time. I dont blame you for asking though. When you look around the internet at some of the advice being given, its a scary place.

Cheers.