Bosch mechanical pump bracket change, smoke when cold

This is the Forum for all your Citroen Technical Questions, Problems or Advice.

Moderator: RichardW

romie
Posts: 451
Joined: 07 May 2010, 14:02
x 2

Bosch mechanical pump bracket change, smoke when cold

Post by romie »

Hiya,

It might just be coincidence, but after replacing the Bosch mechanical injection pump's bracket. There seems to be a lot of smoke when starting from cold, which then clears after a few minutes of driving when everything warms up.

There's a build up of black soot inside the exhaust rear pipe.
Also there's quite a bit of 'hunting' when cold. I compensate for this by pushing on the accelerator slightly, or driving harder than normal until everything has warmed up then she's ok.

I'm wondering if this could be a slight timing issue after taking the pump off then replacing it again?

The pump bolts into slots in its bracket, would adjusting the pump backward or forward in these slots make any difference to the smoky/'hunting' starts?

Thanks for any input on this :)

Romie

Citroen Xantia Estate 1.9TD 1996 Bosch mechanical injection pump
Last edited by romie on 20 Jul 2012, 14:27, edited 1 time in total.

User avatar
Chris570
Posts: 1468
Joined: 12 Dec 2009, 15:10
x 7

Re: Bosch mechanical pump braket change, smoke when cold

Post by Chris570 »

romie wrote: I'm wondering if this could be a slight timing issue after taking the pump off then replacing it again?
You sir are bang on

romie
Posts: 451
Joined: 07 May 2010, 14:02
x 2

Re: Bosch mechanical pump braket change, smoke when cold

Post by romie »

Chris570 wrote:
romie wrote: I'm wondering if this could be a slight timing issue after taking the pump off then replacing it again?
You sir are bang on
(wish me ignition was 'bang on') :p

oooOOOOooooo Fantastic q^^p

Thanks Chris570! don't suppose you could spare a little time explaining what's going on could you?

Lets see, adjusting the pump forward/backward just advances or delays the, (relative to piston position), time at which fuel is injected, yeah?

... and so if it's a little to advanced, then we're not getting the optimum atomization and so some fuel is not getting caught up in the flame front - result over fuelling on next cycle = smoke.

... or little too delayed then.. hmm, this needs a little bit more knowledge I think. Erm, injection of fuel too close to TDC and so again build up of un-burnt fuel for next cycle = smoke... but this wouldn't rectify itself so easily with the addition of heat to burn everything off.... sooooooo, I must have too much advance? .. so I need to delay?...

This sound bout right? :/

And if so, then I need to delay and so rotate the pump backward toward the engine in it's slots? (not forward, away from the engine).
I'm a little bit vague on the above - head starting to hurt with advances and delays :(

What you think?

romie
Posts: 451
Joined: 07 May 2010, 14:02
x 2

Re: Bosch mechanical pump bracket change, smoke when cold

Post by romie »

hmm, I spelt bracket wrong in the title... changed.

romie
Posts: 451
Joined: 07 May 2010, 14:02
x 2

Re: Bosch mechanical pump bracket change, smoke when cold

Post by romie »

Hm. Rotating the pump forward away from the engine made it harder to start with alot more hunting.

Rotating the pump forward away from the engine seemed to make it easier to start but loud knocking sounds started.

I loosed all the bolts and rotated the pump backward and forward with the engine running and in the middle of the adjustment area seemed quietest/smoothest.

This isn't a very fair test as it's suddenly turned hot and sunny so I might not be able to relate the findings accuratly.

I've left the pump adjusted away from the engine slightly so theres a knocking sound. I'll run it like this for a few days and see if it improves the starting and smokiness.

Could this cause any damage to the engine? Please say asap and I'll move the pump back!

Could anyone say anything about the knocking sound?

Is it due to the fuel being ignited too soon and so causing the piston to kick back before TDC?

Is it because the fuel is being injected earlier? But it can't detonate earlier because of this can it?

Detonation is on compresson and so this cannot be adjusted can it?

:/

Sorry as you can tell I'm a bit vague on this, many thanks for any thoughts guys

Romie

Peter.N.
Moderating Team
Posts: 9728
Joined: 02 Apr 2005, 16:11
x 265

Re: Bosch mechanical pump bracket change, smoke when cold

Post by Peter.N. »

Advance the pump by turning clockwise untill it starts to knock then turn it back until it just doesn't. You can turn it smoothly with the engine running by pushing a tyre lever between the injection pipes at the back and levering, as soon as it sounds right tighten one of the nuts, that should do it.

Peter

romie
Posts: 451
Joined: 07 May 2010, 14:02
x 2

Re: Bosch mechanical pump bracket change, smoke when cold

Post by romie »

Many thanks Peter.N. :D

steelcityuk
Posts: 1053
Joined: 03 Jul 2006, 21:51
x 1

Re: Bosch mechanical pump bracket change, smoke when cold

Post by steelcityuk »

Here's how it's done with dial gauge.
Image

Steve.

romie
Posts: 451
Joined: 07 May 2010, 14:02
x 2

Re: Bosch mechanical pump bracket change, smoke when cold

Post by romie »

Hmm, what's the dial gauge measuring then? I suppose it would be checking TDC of the main plunger inside the pump against a timing mark on the fly wheel and working out the angle it should be at from that? - or summit :/

Anywho, I rotated the pump back so there's no knocking (sounds smooth and quiet), but I'm back to more smoking and hunting :(

I'll have to rotate back to knocking and look up what's going on and the best way to improve matters. ugh.

Peter.N.
Moderating Team
Posts: 9728
Joined: 02 Apr 2005, 16:11
x 265

Re: Bosch mechanical pump bracket change, smoke when cold

Post by Peter.N. »

You don't want it dead quite, just a gentle knock will do. You should be able to advance it until it runs evenly, to retarded it will be quiet and difficult to start.

Peter

romie
Posts: 451
Joined: 07 May 2010, 14:02
x 2

Re: Bosch mechanical pump bracket change, smoke when cold

Post by romie »

cheers Peter, adjusted to slight knock starting well without hunting. ta