Expert/Xantia injection pump extra wires

Wookey · Unread post by **Wookey** » 18 Dec 2010, 19:59

I put a Xantia TD into an Expert D back in 2005. Having just looked at my pump (see alarm/immobiliser thread) I notice I have an extra widget with some wires from a connector which was presumably used on the Xantia but there is nothing in the Expert wiring loom to correspond. It's been working just fine for 5 years so it obviously isn't that important but there is some kind of thing that the wires go to, so it'd be good to know what it is and what it should be connected up to:

Here's a view from the RHS showing the unused connectors:

Any suggestions welcome.

Also - whilst I'm here - the new engine has always run quite cool (according to the thermostat), and it does take a while for the heater to get hot. Does anyone know what the correct thermostat temp for a 1995 Xantia 1.9TD is? I guess I should ask that over on the citroen forum.

Cheers

Xaccers · Unread post by **Xaccers** » 18 Dec 2010, 20:19

Cold advance if memory serves, the old fully mechanical pump I've put on Cassy has the same, and it's not connected up either

Temperature wise they should run at 80C, although at the moment with such cold weather Cassy's running at 70-75C.
I've just replaced her thermostat though as before that she'd started running at 60C which is way too cold.

spider · Unread post by **spider** » 18 Dec 2010, 20:55

I'd agree cold start advance, I threw mine away actually (and the module screwed into the (Lucas on mine) pump. You can't do that on a Bosch pump easily though, but just ignore it. The other wires were probably transponder / keypad stuff (again not needed now)

The cold start advance would only work when the throttle / control cable was shut (ie idle only) and the waxstat cable if fitted was tight (ie engine very cold)

Does not really make any 'real' difference that I have noticed apart from a slightly more smelly exhaust when the weather is like it is now and the engine is cold (ie: it stinks a bit when you are outside de-icing)

Although today I was also de-icing the inside ( ! ) of the glass too

Unread post by **CitroJim** » 19 Dec 2010, 09:24

Yes, it's the cold advance electrovalve. It is active (12V applied to it) when the coolant is below 60 degrees, glowplug post-heating is operative and the throttle is less than one third open. The purpose of the microswitch on top of the pump is to cancel both post-heating and cold advance when the throttle is beyond a third open.

I've never noticed it does very much. You can hear a slight change in engine note when the engine is really cold and that's about it.

If you want it in operation and the car was not originally wired for it (such as yours Xac) you can wire it to the glowplugs. Then it'll be operative all the time post-heating is in operation.

Post-heating (glowplugs continuing to heat after engine start) and cold advance is under ECU control in later engines.

Wookey · Unread post by **Wookey** » 19 Dec 2010, 19:36

Cheers for those answers. So it's correct that the glowplugs operate after the orange light goes off? How long for? Until the throttle reaches 1/3rd and pushes the microswitch (or the ECU turns it off on more modern engines?).

If I connected it to the glowplugs that's means it would come on all year round. I guess cold start is always fairly cold even in summer so that'd be OK?

spider · Unread post by **spider** » 19 Dec 2010, 20:13

On initial switching the ignition on the following happens (I'm assuming you do NOT attempt to start it)

The glowplugs (via the relay) are powered along with the light.

After a few seconds (temperature dependent) the glowplug light goes out, typically 6 to 10 seconds. This is the normal stage to start the engine.

The glowplugs remain powered at full power for anything up to another ten seconds (only if you do NOT attempt to start it), this is mainly to help you if you were not watching the light.

Note: as soon as the starter is engaged the glowplug power is cut off

All that information above is pre-heating (ie: before starting)

Post heating:

This powers the glowplugs at a lower power setting for a short time after starting, its supposed to help reduce emissions and suchlike along with the cold start advance.

As Jim has said, this depends on various factors to work, the acc must be shut or almost shut, and the engine cold.

There is no 'need' for post heating in this country and you will probably not notice any different if it was removed, probably

, assuming it worked anyway.

Pre-heating is needed however, although very old engines had just a manual preheat switch and nothing more. You simply applied this for a short time before starting.

Summary: You only need the pre-heating to work, the post heating stuff is not really needed in my opinion.

Note: I'm just working on my understanding of it, hopefully its correct and should help you a bit.

Unread post by **CitroJim** » 19 Dec 2010, 20:18

spider wrote: Note: I'm just working on my understanding of it, hopefully its correct and should help you a bit.

That's pretty much spot on by my understanding Andy, excellent.

Indeed, in an IDI (InDirect Injection) engine (of which the XUD is) it is the pre-heating which is vital. Only the turbos had post-heating. The NA engines lived happily without it.

Even in the tropics an IDI engine will struggle to start with no pre-heating. Conversely a DI (Direct Injection) engine like the HDi needs no heating at all unless the brass monkeys are out in force.