ZX diesel cutting out when cold

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andy46
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ZX diesel cutting out when cold

Post by andy46 »

Hi. I have a 1996 ZX 1.9NA diesel estate, it normally runs very well, I've had it for 18 months with no problems.
In this really cold weather it has started to cut out when I take my foot off at junctions etc. It "bump" starts by leaving it in gear and using what momentum I have while putting my foot back down but this morning the engine actually stopped and was difficult to restart.

The problem only appears on the early morning run of about 10 miles, I do the run 4 times a day and it seems fine at other times.

I changed the fuel filter yesterday in case there was water in it which was freezing but it was OK - changing the filter hasn't affected the problem one way or the other.

A workmate says he had a similar problem on a Pug 306 and that he changed the coilpack (think he meant the heater plugs) and cured it. Could that help? I thought the heater plugs only helped the engine start.

It is a little more difficult to start in the cold but it's a 17 year old car that's done 150,000 miles. The heater plug light on the dash seems to go out sooner than I would expect.

Any suggestions please, I don't want to change car just now as I have recently invested in a new exhaust and 6 months tax.

Thanks
Andy
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Re: ZX diesel cutting out when cold

Post by Chlorate »

No coil packs on a diesel, the glow plugs run on 12v direct from the battery.
I wouldn't think faulty glow plugs would cause the car to die whilst running, as you say they're only needed to start the engine from cold.

I had a similar problem with my ZX, generally when I had my foot off the accelerator for a while going downhill it would stall when I declutched and could be started again by re-engaging the clutch (it is not advised to do this, clutches don't like it). I never did figure out what was causing the problem however I suspected that the stop position on the fuel pump wasn't set correctly so it wouldn't fuel for idle if the revs suddenly dropped. However this didn't happen more in the cold and the car was generally a good starter.

I would say that this is probably a fuel related issue however...

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Re: ZX diesel cutting out when cold

Post by Peter.N. »

The first thing I was going to suggest was the filter but its obviously not that. When it starts does it run evenly on all four cylinders or does it missfire/run unevenly? If so glow plugs will likely be the problem, as well as starting the engine they also aid combustion when cold, although if you have time to reach a jucntion they would have gone off anyway by then.

It sounds likely that air is getting into the fuel, next time it does it try pumping the primer until its hard and see if it starts, if so you have an air leak. When the fuel is cold it is more viscous and so more difficult to pump so the extra effort required may be pulling air in somewhere, a partially blocked filter can cause this.

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Re: ZX diesel cutting out when cold

Post by spider »

Does the engine idle slightly higher than normal when cold or does it try to idle too slowly ?

It may be the wax stat which operates the idle control has gone, these do fail after a few years. Easy to replace though and not expensive.

How to check (say if you need more information)

With a stone cold engine (no need to have it running at all) look at the thermostat housing, you'll see a large alum plug screwed into it with a bowden type cable coming out going to the fuel pump. Basically, it pulls the cable when its cold and releases it as it warms up.

Examine the pump end of the connection, it should have pulled the fast idle arm a bit (usually to its stop but not always)

Make no adjustment at this stage but look carefully how much it has pulled the cable or otherwise, if its slack then its certainly got a concern, Assuming its not slack drive the car as normal and when you get a moment (when the engine is hot) examine the cable end again, it should this time be loose (a couple of mm at least sometimes up to 10 or more) and not holding the arm at all.

I don't think you'll find it holding it as otherwise you'd have a too high idle when it was hot but I suspect you may find its not working which can cause stalling when stone cold.

A temporary work around or something else is the anti stall adjustment however that's best done with a hot engine and if the cold start cable is not working properly it will not cure a cutting out concern when cold.

Regarding heater plugs, yes they are used when cold to provide warmth to allow it to actually combust the fuel as the air despite the immense compression is not quite warm enough with a cold engine.

Some engines have what's called "post heating" basically the plugs are kept on for a short time (a couple of minutes) when its running usually at low rpm only or low temps however in most cases if post heating was not working at all it would not have a massive effect, its mainly to cut noise and emissions slightly when cold rather than a running aid as such.

Hope that helps a bit.

There are other causes however in the cold weather it was the first though I had, if it cuts out when hot then most of this post is probably not relevant.
Andy.

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Re: ZX diesel cutting out when cold

Post by caspar »

Had the same problem with my 1.9D a couple of weeks ago.
I fitted clear fuel lines (pvc from B&Q £1 odd a metre) and could see there was air in the diesel.
I suspected the thermostat in the fuel filter assembly as this is sealed with an o ring.
I had previously removed the thermostat innards so the fuel is heated all the time as I was experimenting with vegetable oil. So I removed the filter assembly, cleaned the thermostat area with solvent cleaner and permanently sealed off the thermostat with JB Weld ( similar to araldite) and left to set overnight.
No problems with starting or cutting out since and no air in the diesel.
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Re: ZX diesel cutting out when cold

Post by spider »

Confused as these are separate items.

There's the thermostat for the coolant itself, ie top radiator hose.

There's the waxstat cable for the fast idle when cold, screwed into the thermostat housing (although it should function anyway as its on the 'inside' of the housing)

There's the fuel heater on top of the thermostat housing that the fuel filter base is sat on, the small white 'screw' in the side is the waxstat for that which allows the fuel to be heated if the fuel (fuel not coolant) is below a certain temperature.
Andy.

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Re: ZX diesel cutting out when cold

Post by caspar »

Sorry for the confusion, i'm referring to the white waxstat in the side of the plastic fuel filter housing.
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Re: ZX diesel cutting out when cold

Post by spider »

caspar wrote:Sorry for the confusion, i'm referring to the white waxstat in the side of the plastic fuel filter housing.
Figured you did mean that, no problem at all :) :) :)

Just mainly added the extra stuff in case someone found this topic via a search in the future and wondered what was meant.
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Re: ZX diesel cutting out when cold

Post by andy46 »

Thanks for all the replies, this is all really helpfull stuff.

I think I can safely rule out glow plugs as anything to do with it cutting out.

I've had a look at the fuel pump and idle settings, the fast idle arm appears to be against the stop whether the engine is cold or hot, I suspect the waxstat has failed in the past and this was a way around fixing it. the car idles at 1000 regardles of temp. (except when it cuts out of course). Is that high? I've never taken any notice before but I would say it has been like that since I got it.

The car has always warmed up quite quickly - up to about 87 on the guage within the first mile, the problem with cutting out is happening at all engine temps but only at very low outside temp.

So air getting into the fuel seems likely but only when the outside temp is very cold.

But what about this other waxstat that allows fuel to be heated when it is below the correct temp, if this has failed could this be giving me these symptoms or making the fuel "gloopy" enough to pull some air in?

Also can someone give me part Nos. or proper names for these waxstats as the local motorfactors looked puzzled when I explained that there is an actual cable attatched to the fuel pump, operated by a thermostat - I think they have a better understanding of electronic engine management.

cheers
Andy
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Re: ZX diesel cutting out when cold

Post by mirafioriman »

Interesting thread this. I too would like to know more about the fuel heating side of things as my Xantia 1.9d seems to run a bit rough in the colder frosty weather but really well when it is milder.
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Re: ZX diesel cutting out when cold

Post by spider »

The fuel heating waxstat is part of the fuel filter housing its not available as a separate part as far as I know. They are a pig to take out and even worse to get back in again (sealant is needed I think)

If the fast idle arm is up against its stop, that's not ideal but that is the 'cold' position so its not going to make it cut out just make it idle a bit high as its doing, normal idle should be around say 850 ish. But don't adjust that as you'll make the cold running worse.

The only other thing you may have look at the fast idle arm, is there any wiring on it ? , a plastic / rubber button with a single or two wires on it ? , some NA don't have them this can advance the timing a bit but I'm not sure if that would cause cutting out it should actually prevent it on a cold engine.

I don't think its cold enough here to get waxing in the fuel (the fuel is heated to stop it waxing as it won't go through the pump if it does) but I think in most cases if it waxed up it would just stop and that would be it, you'd have to clean the pipes and replace the filter to make it run again.

Try this for now:

Before starting in the morning:

Open the bonnet and find the primer bulb. Squeeze it a few times then switch the ignition on (do not start just turn to second position) return and squeeze the primer a few more times, say three or four.

Shut bonnet. Switch ignition off, wait a few seconds then switch on and wait for glow plug light etc to go out then start as normal.

See if there's any improvement.


@mirafioriman , its just a valve that allows the fuel to get on the housing top when cold to be warmed via the heat transferred from the metal of the thermostat housing. In theory you could remove the valve and blank it so fuel was heated all the time but I've yet to check that out. My 205 had the silly "back of block" heater and I could not fit the "top hat" one due to the pipework and oil cooler location (upright filter due to radiator) so I made one out of two pieces of copper pipe, one to the bottle return so it got warm quick and the other in the feed before the filter, it worked very well.
Andy.

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Re: ZX diesel cutting out when cold

Post by andy46 »

Okay, further investigation has revealed that when pumping the primer bulb, fuel seeps out of the filter housing. It is coming from a white cross/round shaped bit towards the rear and on the driver side of the housing - is this the waxstat already mentioned?
I guess that if fuel can get out then air can get in so this would look like my problem. It looks like the housing needs to be removed in order to make a decent job of sealing this so I might just order a new one and fit that. Any ideas of part No? Local factors are stumped and I'm currently waiting for the Citroen dealer parts dept to call back.

They have literally just called as I am typing - £64 + VAT. part no 191141. can anyone reccomend an alternative supplier?

Taking it off and sealing it is looking like a good idea.
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Re: ZX diesel cutting out when cold

Post by evilally »

Good find chap. They are relatively easy to reseal. I used Loctite silicon gasket seal on the base, and some araldite to seal in the thermostat. Worked great, no need to purchase a new one.
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Re: ZX diesel cutting out when cold

Post by caspar »

Hi
Yes just remove the filter housing, clean well with alcohol to remove all traces of diesel and use araldite or maybe silicon sealant.
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Re: ZX diesel cutting out when cold

Post by andy46 »

Just a final note to say I took the filter housing off yesterday, cleaned it, sealed the thermostat with araldite and put some gasket sealer on the rubber ring.
The car now starts easily from cold when the light goes out and no more cutting out.

thanks again
Andy
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