Glwo Plugs - starting niggle

[vince]

Hi guys, reading another post has prompted me to look further into an issue id like to resolve on mine.

1995 Xantia TD

When i had the head work done on mine a while back a brand new set of Beru glow plugs were fitted. Since then the car never fails to start or has any problem starting for that matter...but if started in the morning (ie after being parked all night) the car starts but needs a tad of throttle and smokes alot for a few seconds then clears and then is fine.

It never does this when parked for even a few hours and then started, like if we go somewhere shopping or something, it just fires up and not a sign of smoke.

I have also noticed that leaving it a short while longer after the glow plug light goes off helps eliminate the problem in the mornings.....

I cant see the plugs being duff as we sell dozens of them and have never even heard of a problem....so was wondering what else if anything it could be?

[Peter.N.]

Could be air getting into your fuel system allowing the fuel to drain back to the tank when stood for long periods. Try pumping the primer until hard before you start, if it starts OK then, that's what the problem is.

[vince]

If that was the case Peter then surely it wouldnt make any difference if you left the interval longer from ignition on to turning the key would it That almost eliminates the issue....

[CitroJim]

Vince,

I've known this to be the case in the past. My old "sinker" TD suffered this to an extent and I never really got to the bottom of it. It was not glowplugs and was not any air leaks. It was just something the car did.

At near 200K I suspected it was a combination of slight engine and pump wear. Possibly a slight fall in compression possibly due to valve wear. In my case it was made worse because the cold idle speed control was defunct.

The strange thing was, if left a week or more the first start after such a long stand would be perfect and would not exhibit the symptoms at all. It would be a clean instant start with no smoke or fuss. Leave it overnight and the first start would be lumpy and smoky for a few seconds after. A double glowplug application did help, along with the application oif a bit of rev.

Two very important things to check is that your cold idle speed control is working and that your cold start advance system is working.

The former is controlled by a waxstat screwed into the thermostat housing and they often fail. Mine had and I never replaced it. The idea behind this waxstat is that when the coolant is cold it increases the idle speed to about 1100rpm by pulling on the cable between the 'stat and pump. If all is working OK here the idle speed will start out at 1100 rpm and fall slowly to 900 rpm as the engine warms. If the engine starts off at 900 rpm cold it will be a bit lumpy and smoky at the beginning.

Check the cold start advance is working by checking that 12V is present at the cold-start electrovalve that can be seen on the front of the pump with a brown wire going to it. 12V should be present whilst the glowplugs are post-heating (i.e. still glowing after initial start). The cold advance will cancel at the end of post-heating when the coolant reaches 60 degrees or you rev beyiond 1/3rd throttle or whichever occurs first.

In fact, do check that glowplug post-heating is in fact working by checking for 12V at the glowplugs themselves just after a cold start. The post-heat should go on for about 3 minutes or until 60 degrees or 1/3rd throttle is reached as for the cold-start advance. If the post-heating is not working, the engine will again run a bit lumpy and smoky initially.

Cold-start advance on a diesel is important as cold diesel takes a while longer to get burning than does hot diesel.

Hope that gives you some pointers Vince.

Note that all this only applies to the early 1.9TD with the fully mechanical pump (as yours is Vince). The later ones with the AS3 pump do all the same things but under ECU control.

[tonupteabag]

i had the same thing with a rover 218sd it still uses the peugeot diesel same as the xantia it turned out to be the valve clearances on the intial start it would be lumpy then within a second or so would run evenly my xantia does the same thing so i just give the glow plugs two hits first thing and it starts evenly as you say it only does from being left overnight the rover had done 108,000mls when this starting issue showed up and the xantia has been doing it since 104,000mls i have changed the glowplugs aswell

[xmexclusive]

Colour of smoke can sometimes be a useful guide.
Blue/Black from part burnt fuel would tend to confirm poor glow plugs.
White from weak fuel mix would suggest air in the system.
Overnight fuel run back from a minor air leak is a very common problem that is difficult to pinpoint because the split can be very small with no external fuel leakage at all. Rubber fuel pipes running over the top of the engine commonly harden with age and split close to a fixing on the rear bulkhead. If slow air ingress is suspected then a temporary fit of short lengths of clear pipe either side of the squeeze bulb will show that air is getting in.

John

[Peter.N.]

If that was the case Peter then surely it wouldnt make any difference if you left the interval longer from ignition on to turning the key would it That almost eliminates the issue....

Sorry I hadn't read the post properly - as usual. I always leave mine until I hear the relay drop out, it then starts instantly. If two applications of heat improve the starting then as Jim says I would suspect low compression.

Peter