Froggy in the place :)

[johnjohn]

Hello all,

My name is John. Living in France.

I bought XM 2.5 TD Exclusive for few euros with 220 000km.

I already changed many parts as:
- Timing belt
- Brake Pads and Disks
- Interior Screen
- Seals of injector pump
- Hoses


now one remaining issue regarding start of engine.Not Starting very well and I don't know why

[Dieselman]

Suspect an air leak at the filter head or fuel heater.

[White Exec]

Hello John, and welcome to the Forum.

This is a good place to have landed, and you should find lots of help and useful info here, not least on the 2.5.
Do post some photos of your car, and also its RP/ORGA number (4 painted digits, between the hinges on the front LH door), and also the car's VIN number. Both of these help no end in correctly identifying parts, equipment and wiring diagrams.

On the poor starting, worth checking...

Glow plugs
Should be receiving a minimum of 11v, and taking about 9-10A each (40A total) for a cold start.
Check also the GP relay, especially its underside contacts; these can overheat/become corroded and need cleaning up.
There are relay contacts inside the unit, which can be opened up to examine.
The GPs themselves can be easily removed, and bench-tested individually. With 12v applied, the tip should glow orange-hot within 5 secs or so, and each one take about 10A. If replacing, BERU brand is recommended.

Main battery connectors
Check whether either of the main battery connectors (lead (Pb) lumps, if still original) gets at all warm when cranking the engine. These can develop poor connection internally, and are best replaced with new brass clamps.

Battery voltage
Should be around 12.5v with everything switched off, and before attempting to start.
With engine running, voltage at the battery (fast idle) should show 14.4 - 14.7v if the alternator is doing its stuff.

Air-in-fuel
Air trapped in the fuel supply will make starting difficult. Check by pressing the priming button (on top of the fuel filter) before trying to start a cold engine. If the button feels immediately solid (after no more than a single pump) that is a good sign; if it needs several pushes before feeling solid, that indicates there is air in the fuel. A good few pumps may help the engine to start. One known air-leakage point (the delivery pipe is under suction - the injection pump sucks fuel from the tank) is the fuel pre-heater, at the air cleaner end of the engine block. These cast aluminium blocks can go porous, and let air into the fuel. The units are frequently simply by-passed (join the fuel lines), i.e. jumped out of circuit, but left in place.

Let us know how you get on.

[johnjohn]

Hello

Thank you so much for 1st answers. It seems a very active forum.

- Regarding Glow Plugs I already changed them with Magnetti Marelli ones, too late for Beru. Regarding GP relay, I cleaned all contacts with sand papers and open it to re do all soldering points. I cleaned all contact inside also.

- Battery connectors I will check! Didn't do anything on this.

- Battery voltage no issue. This one is new with 12.6 at idle

- Air in fuel: I revised pump completly with new seals. I have translucide hose also to check if any bubble but nothing. Button is very very hard. Pre heater is by passed.

[johnjohn]

What I would like to do is also to replace harness to Glow plugs. Why ? because i have 11.5v under the realy and 10.6 to plugs...

Seems very strange...

On additional strange thing is when im pre heating. Light is turning on after off but one blinking appears.... Dont know how it is possible.

[White Exec]

The single cable running from the GP relay to the GP 'rail' can suffer deterioration.

On the 2.5, I reckon it's also under-sized for the job it has to do. A large cable arrives from battery to the GP relay, but the one leading away from it is only around 2.5mm2, which makes no sense. I would suggest replacing the cable, and with 4mm2. I did this here, and there was a marked improvement in GP performance. A new cable can be run along the same route as the old one, after it leaves the battery box area.

A thread here discusses it: viewtopic.php?f=5&t=9262&p=112050#p112036 .

The GP 'rail' (cable with 4 ring connectors) can also suffer from poor connection, and would be worth cleaning up.
If there is any swollen insulation near to a connector, it's a sign that the connector/cable has been getting hot.

Brass battery connectors could be something like these...
.

Battery clamp connector pr.jpg

Also worth checking the heavy-duty "take-off block" a short distance from the battery+ terminal, where several cables take their + supply. It's just to the left of the GP relay in this photo, behind the radiator top corner...
.

Pre-heater relay.jpg

.
Can you clarify what the pre-heat dash light is doing?

[johnjohn]

Thanks Chris.

When I'm turning key for pre heating, light is on and turning off. One or two second after ligh is blinking one time very quickly like a flash.
I thought it was the GP Relay but even when I'm replacing it by a second one ... same behavior.

[White Exec]

The GP light shouldn't be flashing. Suggests a fault, although I haven't been able to find reference to it flashing in documents, yet. Light should just illuminate when IGN is switched on, and then extinguish when OK to start. Pre-heating will continue after the light goes out (time depends on coolant temp), and post-heating (0-3mins, again depending on coolant temp) immediately after starting.

[Silly thought: a flashing ABS light isn't uncommon, indicating an ABS fault.]

The GP light is controlled by the GP relay, in turn taking command from the injection (engine) ECU. The behaviour of the GP relay is thus determined by sensing (via the inj ECU) coolant temp (the Green temp sensor on the water outlet/thermostat). [The other two sensors are Brown=fans control, and Blue=gauge/'dial'.]

Might be worth checking connections to all these things:
- Green temp sensor (unplug it and see if any difference)
- 55-way ECU connector
- 5-way connector on GP relay

Gabor's (downloadable and printable) circuit diagram will help, if you haven't got it already:
viewtopic.php?f=13&t=7592&start=60#p112051
See p.10 for GP circuitry.

Lexia should show a fault; not sure if you have access to one.

Could be worth either rigging up a test-lamp to the GP rail (and/or using a voltmeter there) to check whether post-heating (as well as pre-heating) is happening on a cold engine. Worth noting that some GP relays do not have a post-heat function, and always possible that an incorrect one has been fitted; if post-heat doesn't happen, would be worth checking out.

[johnjohn]

Hello Chris,

Thanks for diagram this one is very nice, I didn't have this version.

Regarding, checking connection I will do today and will let you know.

About Lexia , I have one but I don't know how and where to plug it. I will make a search in this forum . SHould be there.

I can give you my voltages:
- Battery idle 12.6
- GP relay in 12.6
- GP relay out 11.5
- GPs 10.6

I will set new cables today in 4mm². one between battery and relay and 2 new ones to GPs.

What do you think about engine starter? Could be also a possibility?

[johnjohn]

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