bx td rough idle + smoke when cold

freek · Post by **freek** » 13 Mar 2006, 21:23

Hi,
I have a similar problem as 'Smokey Joe' (5th march). Some history: a few month ago I replaced the Roto diesel pump on my BX turbo diesel. I adjusted the timing by trial and error and am in fact very satisfied with the result: almost no smoke when speeding up and a very quiet engine when warm. I have only one problem: when starting with a cold engine in the morning or after several hours the car produces a lot of smoke and runs unevenly for say 20 seconds. The engine starts however instantly. I first checked the glow plugs by checking whether they would glow in 10 seconds when connecting them directly to the battery. This was the case. Secondly I thought that may be the timing is a bit retarded so I advanced the timing a bit (in contrary to earlier posts on this subject this is a very accurate job) I advanced the timing by turning the pump 1 mm clockwise (looking from the gearbox) but this resulted in more smoke when accelerating and not less smoke when starting. I also suspected air in the fuelsystem, so I replaced the hand pump + filterhousing by another used one. This also had no effect. Although the engine uses some oil (1 ltr on 3000 km) it is quite fast and behaves not as one which is suffering from low compression. My questions are:a) is there a chance that the injectors can cause these symptoms? b) the knob on the handpump feels soft after a while when pumping until is feels hard; could this mean that air is entering the system (sorry i have not munted yet a clear plastic fuel line) c) the pump has a electric advancing mechanism which is switched on by the wax thermostat; could a malfunctioning device cause the problems described?
Regards,
Freek

Mandrake · Post by **Mandrake** » 13 Mar 2006, 21:44

You checked the glow plugs were ok by directly connecting them to the battery, but maybe the relays or wiring that feed them are not ok ?

Is it possible to measure the voltage on the glow plugs terminals in situ ? As they draw so much current even a bit of resistance in the relay contacts or poor connections in the wiring may cause a large voltage drop...

Sounds like you have problems with the fuel line too if the bulb is soft, although I'll leave that to someone with more diesel experience to answer

Regards,
Simon

jeremy · Post by **jeremy** » 13 Mar 2006, 22:16

I can't work out if you have a Bosch or Roto-Diesel pump on your car now. the Bosch is vulnerable to faults in the leakoff system, the Roto-Diesel just leaks and smells.

I think you have air getting in the system somewhere - why not replace the last pipe to the pump with a length of plastic temporarily and look for air. while you have air you will have problems.

Glowplugs could be the problem - check them in position by taking the terminal off the top and meter each one - or use a bulb. They should have a resistance of about 1 ohm. One down will cause smoking.

If you are suspicious of the relay - disconnect the glowplug supply and jump the plugs and see what happens. Connect a jump lead between battery + and one of the plug terminals. (they are connected together and connecting to one will feed all.)

The steel fuel pipes are prone to rust - relatively easy to replace and not expensive from Citroen.

jeremy

Post by **Peter.N.** » 13 Mar 2006, 23:42

If the engine is running unusually quietly, this can be a sign of retarded timing, but as you say it starts OK its probably not that. Advancing the timing will make it start better but also to knock more. I think the previous replies are about right, either air ingress or faulty glow plugs. If one or more glow plugs are not working, the engine will tend to miss on that cylinder when it first starts, giving you clouds of bluish white smoke.

citronut · Post by **citronut** » 14 Mar 2006, 08:44

also check the contacts in the cold start linkage which give the advance retard servo its earth feed,one of my customers ZXs has this device on the pump and it used to smoke whilst cold,after i cleand the contacts it seemed to cure this problem and the car ran a lot better,have you also got the fuel heater in line behind the engine,its the cigar shaped canister in the fuel line from the tank to the filter houseing,what was the reason for replaceing the pump
regards malcolm

AndersDK · Post by **AndersDK** » 14 Mar 2006, 11:43

Jeremy :

The BX turbodiesel is fitted with the CAV (roto diesel) in all Europe mainland (LHD) varities.
I know I keep referring to the diesel distributor pump as a "roto-diesel" althogh I do in fact mean either make (CAV or Bosch) most times

Malcolm :

Yes I believe you are spot on with the contact set on the coldstart device. Just had this problem myself on my BX TD. This however gave me a new symptom I'd never experinced before : the cold engine would instantly stall the moment you let off the acc pedal.

Freek :

This contact set is located (yours) LH front corner of the pump - standing in front of it. Also check the wiring from this switch as it may well be pretty rotten from the road environment. Keep in mind its exposed to salty mist from the cooling air thru the radiator.

jeremy · Post by **jeremy** » 14 Mar 2006, 13:34

Anders - thye reason I asked the question was that Freek stated that he had replaced the Roto-diesel pump but doesn't say what he replaced it with.

I think Bosch-pumped TD BX are dumped in UK - I've seen 2, the first was one of the first DTR Turbo Estates, the second is my neighbours TGD Turbo saloon, (91-92) and this DTR Turbo on E-bay

http://cgi.ebay.co.uk/1989-CITROEN-BX-D ... dZViewItem

My experience of disconnecting the cold start on my Roto-Diesel pump was that the idle dropped and the thing hunted when cold. If it had dropped much more it may well have stalled but there seems to be a limited form of governor that tries to maintain idle speed and prevent stalling - hence the hunting.

freek · Post by **freek** » 14 Mar 2006, 20:36

Hi again,
Thank you for the replies. The pump is in fact a Rotodiesel and the faulty one also was. But I changed the engine 6 years ago. The original engine im my car had a Bosch pump (like the picture on ebay).
Can I conclude from your replies that worn injectors can not cause the problem described? I measured the glowplugs earlier and the resistance was app 0,9 ohm. And I cleaned the contacts of the glow relay but the idea of connecting a jump lead between battery + and one of the plug terminals is a good one to rule out the relay. And I will check the contact set on the coldstart device. Good point! Do you have any idea what the effect of this device is on the timing? Your answers (stalling engine) would suggest a considerable effect. To be clear: the increased idle speed due to the wax thermostat works ok.
Finally I will mount a plastic tube and see what happens.
Hopefully I have good news after the weekend.
Freek

jeremy · Post by **jeremy** » 15 Mar 2006, 10:55

As far as I know the electric advance device on the Roto-diesel pump is an all or nothing device - as its operated by a simple contact on the end of the cable from the waxstat device - and so is either on or off!

If your fast idle is working then this device is probably ok - and to be fair there don't seem to be any problems with them coming up on here (apart from failed waxstat's)

Roto-diesel pumps don't like air - and rely on fuel to operate the governing (control) mechanism which means that they can rev uncontrollably if there is air in the system. They are however totally immune to problems caused by faulty leakoff pipes.

Injectors can cause smoke on start-up but when mine were faulty there wasn't a huge amount of smoke. It did however smell and smoke a bit when hot and needed lots of gearchanging to keep it going nicely. Injector cleaner would produce a small improvement for a short while.

From the timing of your problems I would think the leak if any is close to the pump. I have a minor leak on my TD which starts normally all the time but cuts out if its been standing for a few days. If I hold the acelerator down a little way (1200 RPM) it will continue to run but a rise in revs is noticeable when the air passes through the pump. I must get at it and have a good look!

jeremy