Xantia 1.9 TD Cold starting problems

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BonceChops
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Post by BonceChops »

The only symptoms apart from the cold start problem it that it always ticks over at 1100 rpm hot or cold & is a bit reluctant to pick up from 2500 rpm to about 3000 rpm when it gets into it's stride
That is strange - mine pulls like a train from about 2400 right up to the red line - it is a bit poor below 2400. I dont get full turbo pressure till about 2400. I wonder if yours is under fueling.
pete woods
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Post by pete woods »

My Passat pulls hard from about 2500 as well. Having driven the Xantia again today It does feel like a fuel problem rather than a misfire. The best way to describe it would be to say its like a 2 stroke motorcycle if you open it up before it reaches the powerband.
Pumping the primer makes no difference at all. I think someone has dicked about with it at some point in the past. I need to find a good specialist in the Southeast to have it checked.
KevMayer
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Post by KevMayer »

Pete,
I once had an Audi 80 1.6 TurboD. It had a Bosch pump almost the same as ours. It developed terrible starting problems. It would crank over for ages and not fire up. I had it checked by a local garage who was half interested. He thought it might be an air leak, so supplied the pump from a gravity fed diesel tank. Still no good. So no air leak. He then got a mechanic to crank it while he disconnected a pipe from an injector. We expected diesel to squirt out, but nothing. He tried another. But no squirts. He took the pump off and sent it to Potteries Diesel in Stoke-on-trent. They checked the pump calibration. It was worn out. Too much clearence to develope pressure. So I hadto have a recon pump fitted at around 400 quid.
The funny thing was, when I did get it started, and it usually wasn't a bad starter from cold, It ran really well. Just wouldn't start from hot.
This doesn't tie up with your cold start problem, but it may give you a clue.
I once ended up wit ha high tickover on my Xantia after I had adjusted the throttle position potentiometer ontop of my pump throttle arm. Is that in the right place ?
Hope you have luck soon.
Cheers, Kev
pete woods
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Post by pete woods »

I have no idea Kev. The thing always ticks over at 1100 rpm stone cold or red hot. The injection specialist I spoke to thinks this is the cause of the problem. The trouble is I can find no info on setting up the pump & it looks like everything I need to reach is at the back of the pump body. This means removing half the car to get at it!
I have adjusted the tickover screw a little at their suggestion & will bo the same to the cold start cable & see if this makes a difference.
Any access suggestions would be very welcome as would info on settings
Dave Burns
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Post by Dave Burns »

Pete, Did you have a look at the vacuum avance to see if its working before you go altering the pump settings, if its in fast idle mode all the time it will be permenantly advanced, thats how faster idle is achieved by advancing the timing.
If you start the engine from cold and look at the vacuum diaphragm you should see it pull the cable when you rev the engine if its working ok, beyond a certain temperature or a certain rpm for a cold engine the timing advance is switched off by the ECU, its not good to be running with 2.5 degrees extra advance all the time, and if you go playing with the screws governing the fast idle lever min/max positions you are altering the timing, not just the idle speed.
On a hot engine the ECU also raises the idle speed when the aircon is switched on.
Dave
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Post by BonceChops »

On the tick over speed - is the throttle ( erm must be wrong name for it cus were talking diesels ) linkage touching the adjuster screw at tickover or is it held off it by that damper thing like mine was. Mine is the Bosch pump no ECU.
pete woods
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Post by pete woods »

Damper thing holding it off a little. I have adjusted both the damper screw & the Throttle (?!) screw. Will report on the effect it has on stone cold starts. After a year of looking for leaks, changing glow plugs & general grief & stress how I will laugh if all I needed to do all along was adjust a screw!
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Post by KevMayer »

My Haynes manual says normal idle should be 850 + or - 50 rpm (for a Xantia with aircon). Fast idle should be 950 + or - 50 rpm. So, when the engine is cold and ticking over at fast idle is that something like 2.5 deg timing advance. that seems a lot but if thats the case then my tickover being 800 rpm or sometimes looking like about 780 rpm means that I am running something like 1 to 1.5 deg retarded. I have often reported a suspected timing problem. I may have just found the answer with big thanks to Dave. I had no idea the idle adjustment involved changing timing angle. i've been out an purchased a deep reach 10 mil socket so I can get to the locknut on the normal idle screw. Haven't done it yet. I'll let you know what happens.
Do you think this will make a difference. Will all my ECU advance be based on this initial idle timing setting ?
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Post by Dave Burns »

Thats (Official Bosch publication figure) 2.5 degrees camshaft not crankshaft, measured at the crankshaft it would be 5 degrees since engine speed is twice camshaft speed.
The idle adjustment via injection timing is only affected by the cold start fast idle lever on the engine facing side of the pump, not the main accelerator lever on top of the pump.
The ECU models have engine speed input and injector lift sensor (point of injection) input, the ECU should correct any timing error using this data but maybe its not that smart a system, how important the initial setting is I'm not sure but wouldn't think it could simply be willy nilly and the ECU makes it all right again, thats not how things are in my experience.
Dave
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Post by KevMayer »

Dave,
Could this idle timing setting be the starting point for the roller ring. Then, won't the ECU control timing advance from this starting point. The ECU wont be able to retard the timing, but I see what you mean about the ECU using injector lift plus engine speed and throttle position etc.. to work out how much advance is required ahead of this initial setting.
I will adjust my normal idle and fast idle speeds (including backing off the anti stall screw and resetting it) as per the brief instructions in my Haynes manual.
It will be interesting to see if I notice any difference to my performance. Probably not, as you say, once the ECU takes over the timing advance should be as before.
Thanks Dave, I'm sure everyone here appreciates your help.
KevMayer
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Post by KevMayer »

Pete,
I've adjusted my idle speed and now see how it all works.
There are two screws on the pump, engine side of where the "throttle" lever sits (just under the damper). These are stop screws for a lever beneath. The screw on the timing belt side is for fast idle. It sounds like your arm is stuck on this setting and its set too high. The other screw on the gearbox side is the normal idle setting.
There is a cable on the lever which is connected to the vacuum operated diaphragm near the LHM tank bolted to the inlet manifold (I think).
So, when the engine is cold the vacuum diaphragm is out (i.e. not sucked in) and the lever will be pushed by its spring to the timing belt side. This is the fast idle position. It should be at 950 + or - 50 rpm. Sounds like your stop screw could be backed off too much and giving 1100 rpm. This is one possibility.
Still with engine cold, when you blip the throttle, the diaphragm is sucked in and the lever is pulled back over to the stop screw on the gearbox side. This will be the normal idle setting, but what it is really doing (thanks to Dave's explanation) is reducing the timing of the pump to normal.
When the lever is in the fast idle position the forward movement of the lever has actually advanced the pump timing. The lever being pulled back by the vacuum diaphragm when you blip the throttle is taking away this advance, i.e. putting it back to normal.
But, it sounds like your diaphragm isn't pulling your lever back. It's sticking in fast idle (forward) position.
When the engine is warmed up (when it reaches the first thick line on the temp gauge. is it 60 deg ?) the vacuum diaphragm stays sucked in and pulls our lever back to the normal idle position (i.e. towards the gearbox end). The reduced timing in the normal position reduces the tickover (idle) speed. This should be 850 +0 -50 rpm.
But, your nipple on the end of your cable isn't making contact, and so, not pulling back to normal idle speed.
All the time the engine is warm the diaphragm should be permanently sucked in and lever pulled back.
Dave says the timing angle difference from normal to fast idle (i.e. due to the movement forwards and backwards of this lever) is about 2.5 degrees of injector pump, adn because the injector pump rotates at half the speed of the crank shaft, this equates to 5 degrees of timing advance. So, if your arm isn't being pulled back, you are running with a permanent 5 degree advance (possibly.... but Dave points out that the ECU takes over to control the advance under load conditions. So you may not have 5 deg advance above what is required by the engine if the ECU has chance to do its bit to control timing).
So, sounds like your diaphragm isn't working and for some reason your fast idle stop screw is backed off too much.
Now, what else might it be.
1. possibly the anti stall screw is screwed out too far. If the locknut had come loose on this screw the screw can rotate due to vibration and may have worked itself forward.
2. Have you still got the pneumatic "shock absorber" device connected to your "throttle" are from somewhere beneath the pump at the front. I reported a fast tickover once when I was having a service. The Citroen dealer said it was probably my "shock absorber" not returning properly and holding the throttle on a little. He took the "shock absorber" off. It made no difference to my car, but they ensured me that it had worked on others.
3. As you have already investigated. The damper mechanism could need adjusting. It may be holding your throttle on.
From what you have told us though, I think your vacuum diaphragm isn't working.
I adjusted my idle on Tuesday night. I was thinking of your problem while I did it.
I hope this may give you something to think about.
Good luck,
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Post by KevMayer »

<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote"><i>Originally posted by pete woods</i>

One thing. While the engine was still cold but running I used a screwdriver to push on the lever of the cold start device.As soon as I did the revs dropped away. I don't know if this is significant or not!
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
This is proof. You have shown that pushing the lever back reduces the idle speed. All you need now is to get the diaphragm device to pull it back via the cable. When engine warm, this diaphragm should be permanently sucked in (except for very briefly popping out when you blip the throttle. It then sucks back in straight away).
Dave Burns
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Post by Dave Burns »

Hi Kev, yes I did say that it could be possiblt to be running with permenant cold start advance all the time if the mechanism wasn't working properly, and this is true to some extent but after some more thought and research have come to the conclusion that it doesn't really make much difference to normal operaton at driving speeds.
The reason being that the roller ring is turned through its (approx) 2.5 degrees by the cold start mechanism and the engine speed is increased as a result, but as engine speed continues to rise by means of the normal throttle lever, at a certain rpm timing advance will continue to increase due to further rotation of the roller ring from this setting onwards.
As cold start fast idle speed is forced by artificial timing advance, there is slight overlap period where the engine speed can increase further without adding any more advance since it is allready applied, beyond that certain point normality returns naturaly and correct advance is applied regardless of the cold start position or even the ECU.
Therefore a compounded timing error due to permenantly on fast idle plus normal operational timing advance is not (as was first thought) possible.
Sorry if I've muddied the water again for you[:D]
Dave
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Post by KevMayer »

I understand what you're saying. It makes perfect sense.
Thanks Dave
KevMayer
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Post by KevMayer »

Pete,
How is it going. I'd love to know ?
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