GlowPlugs - Changing - WTF

[Andle]

Think my glowplugs might be at a stage that (some) need replacing (Beru).

Seeking advice on what to test for & anything else that should be done first.

Then - on exactly how to go about changing them - the correct way.

I understand that the job is fraught with risk - and needs to be done carefully.

I'm here to learn.

I am a newbie on the topic - so hoping to open up discussion & explore this topic (will benefit other members too hopefully).

Cheers all,

Andle (Good to be back).

[NewcastleFalcon]

I think you need to wait for someone to come along who has done theirs and everything was straightforward.

My thread on such matters doesnt make for happy reading, probably the one and only time the word "annihilate" has been used in an FCF thread title.

viewtopic.php?t=54768&hilit=annihilate

Regards Neil

[white exec]

What problems are showing up, Andle?

[Andle]

Can't start the car straight away or I get loads of smoke & smell of unburnt fuel in exhaust - and the engine shakes itself apart.

If I leave the key in the position - one before kickover - for 15 mins, then turn kick it over to start the car - it still chuggs like hell, but there is much less white smoke.

Initially the idle is really really rough - but then if I let it run for 15 mins - eventually shes driveable.

Everytime I need to use her - 30 minute procedure required.

15 mins priming, then 15 mins idling - only then I can drive her off!

[moizeau]

Not plugs, HDI's don't need them (unless you live in Siberia or need a regen).
15 mins priming?
Check the EGR in Diagbox

[white exec]

And check for air in the fuel, with a clear hose between fuel filter and pump.
Lots of priming suggests air is being sucked in somewhere. Essential that the pump is receiving air-free fuel.

[jsp]

turn 1/20 right before turning left. After all out put special anti seize on it (grey). torque to spec.

[Andle]

I’m grateful for your responses.

I understand this is not an easy job.

I have a question that is definitely going to upset a few - but by asking it - I am opening up received wisdom for a ‘windows bulletin update’ - in case there’s new information come to light - that hasn’t been widely shared.

Current received wisdom:

HDI’s - the glow plugs are NOT used during startup (EVER),

except ...

in sub zero temps.


Are we 100% sure on this?

[GiveMeABreak]

Glow plugs for older NON-HDI engines were always used to start the vehicle.

Modern HDi engines use high pressure to ignite the fuel.

Glow plugs for modern HDi engines have several functions:

• Pre-heating
• Post-heating
• To assist with regeneration (on vehicles with a diesel particle filter)

It is perfectly normal for glow plugs not to operate at all during the starting phase. It all depends on the engine temperature and the altitude.

So as an example, on your Picasso, if the engine coolant temperature is at anything from 20°C to 80°C there is no pre-heating time, unless at altitudes of over 1000 metres and then only for a few seconds.

Pre-Heating

Engine coolant temperature	Pre-heating time	Idling speed	Altitude exceeding 1000 m	Altitude exceeding 1500 m	Altitude exceeding 2000 m
80 °C	0 seconds	750 rpm	0 seconds	0 seconds	0 seconds
20 °C	0 seconds	800 rpm	0,5 seconds	2 seconds	3 seconds
0 °C	0,5 seconds	890 rpm	1 seconds	5 seconds	5 seconds
- 10 °C	5 seconds	950 rpm	5,5 seconds	9,5 seconds	9,5 seconds
- 20 °C	5 seconds	1050 rpm	5,5 seconds	9,5 seconds	9,5 seconds
- 25 °C	10 seconds	1075 rpm	10,5 seconds	12,5 seconds	12,5 seconds
- 30 °C	15 seconds	1100 rpm	15 seconds	15 seconds	15 seconds

As for Post-heating, the glow plug function is to help reduce emissions in the first few minutes of starting the engine and helps reduce 'blue' smoke. Here is a table showing the times:

Post-Heating

Engine coolant temperature	Pre-heating time	Idling speed	Post heating
80 °C	0 seconds	750 rpm	0 seconds
20 °C	0 seconds	800 rpm	0,5 seconds
0 °C	0,5 seconds	890 rpm	180 seconds
- 10 °C	5 seconds	950 rpm	180 seconds
- 20 °C	5 seconds	1050 rpm	180 seconds
- 25 °C	10 seconds	1075 rpm	180 seconds
- 30 °C	15 seconds	1100 rpm	180 seconds

So to answer your question - it depends, but under normal operating conditions, temperature and altitudes, your glow plugs are not needed to start the engine.

[Andle]

GiveMeABreak,

Your post is clear, precise & conclusive - exactly what I needed.

My sincere thanks.

[ekjdm14]

Allow me to back this up with the information that our 206 1.4HDi has always started perfectly and idled smoothly from cold, even in winter with 4 dead glow plugs (the only indication of the GP's death was the dreaded "antipollution fault" and limp mode, it still started/idled/ran perfectly aside from that).

Also, despite taking all necessary care and precautions, I ended up breaking off the tip of one of the plugs in the head. It was stuck fast with carbon deposits and I believe there was no avoiding the situation & no magic potion that would've freed it up enough to not break, just "one of those things" and we pulled the head off to deal with it.

It was not for shifting any other way, I tried drilling/tapping and using a slide hammer arrangement to no avail, also tried drifting it out, no dice. Only way that one came out was to drill it out, not a step I took lightly & indeed I bought a used complete head as a backup in case things went wrong.

Having said that though, it's not the end of the world IF they were to need doing and were as solid as that one, just don't run with the tip lodged in place, Neil's experience proves the law of sod (no matter how solidly jammed in, if it comes loose it WILL go into the cylinder and not pop out as you'd expect!.

With all this said, your issue is most certainly not caused by glow plug failure. (just posting my experience for the "record" so to speak). My vote goes for air in the fuel also, possibly leaking back overnight.

[Andle]

Here in lies the mystery,

If Inprime the car for 15 mins - the puff of smoke is brief & the chuffing is shorter lived & she idles better.

What is it about the priming - that seems to improve the situation?

Why does 15min of priming improve the start up?

[white exec]

15 mins of priming should never be necessary.
What priming does is pull fuel though the filter, and drive it through the pump. In doing so, it will do its best to drive out any trapped air in the supply to the pump, and it is this air that causes hesitant starting and smoke.
No more than half a minute or so of priming should ever be needed, and as soon as the priming button (or bulb) feels solid, the priming can stop.
Check for air in fuel, and any non-return valves in the filter.

[Andle]

Question:

If there was an issue with one of th glow plugs or with the relay - wouldn’t the engine management light come on?

[GiveMeABreak]

No