V50 Engine 2.0D : V50 Glow plugs duration after start up.

[allanw]

Having read through many posts on here regarding glow plugs, they mostly seem to be problems with poor starting. I do not have that problem. The engine starts even at recent -5 temps no problem, but then runs rough for a few minutes after which it runs fine. I fitted 4 new glow plugs a few weeks ago and they receive power for about 5 secs at start up then shut down no matter what the ambient temp The glow plug light stays on only for a split second. As with other diesels, I believe they should stay on for several minutes to aid combustion after cold start up and stop rough running. Does anyone know what sensors are involved in determining the duration apart from coolant temp sensor ? I can see a sensor behind the oil filler tube that has no push fit connector to it ? Anyone know what it is and where its powered from ? It has been connected in the past as you can see the witness marks. I also changed the glow plug relay but no difference. Any help gladly accepted.

[cheshired5]

Originally Posted by allanw

The engine starts even at recent -5 temps no problem, but then runs rough for a few minutes after which it runs fine.

With rough running for that length of time, I'd be looking more towards oil level, spec and quality.

[allanw]

Thanks for reply. New synthetic oil a few weeks ago. Oil level between max and min. Its more an incomplete combustion problem when cold for a couple of minutes, not bearing knocking or piston slap. Glow plugs should remain on to help combustion of cold engine and therefore emissions. It's a Euro 5 engine. Its what sensors the ecu uses to determine this I am struggling to find out.

[MDS40]

New to volvo but my Jag x type diesel had the after glow system you mention.
This was controlled by the ecu with reference to the cylinder head temp sensor along with the ambient temp sensor to determine the time the plug continued to glow. This would also switch off over 2000 rpm.
Would check if yours has a cht sensor, if so it could be giving too high a reading.

[cheshired5]

Vida normally confirms the glow plug heating sequence so what is the engine code and model year?

Dependant on coolant temperature, my sequence for example is
Preheating
Start standby preheating
Start heating
Afterheating
...... but it doesn't continue for the length of time you suggest in fact on an ambient starting temperature above 8°C the glow plugs don't work at all.

I have a Euro 3 though hence needing more detail on yours.

[Bendolfc]

The natural suggests that they aren't even used below - 2 degrees although that does seem a bit cold to me.

"6. Engine preheater (diesel)
This symbol is lit during engine
preheating. Preheating occurs
when the temperature is below –
2 °C. The car can be started once
the symbol goes out."

[allanw]

Thanks for your input guys. Car is 2005 V50 2.0 litre diesel. 136p.s. Euro 5 with DPF. I have not had much to do with this particular engine until recently but I know that other manufacturers use post start heating e.g. ( VAG & BMW ) to help with emissions and the glow plug light extinguishing on the dash is only an indication when to start the engine and not an indication of glow plugs energised and I assumed this euro 5 engine would be the same ? Maybe this direct injection engine does not do this.
The missing sensor connector is still a puzzle behind the oil filler and near the thermostat housing / manifold. It is difficult to see tucked in there but it is there for a reason. I found the 2 pin connector lying in the under tray but can't see where it's wired from ? Now have a new problem with intermittent hesitation when accelerating that's like a petrol engine flat spot. Maybe should start a new post on that.

[MDS40]

Intermittent hesitation could be due to the egr valve not closing fast enough due to being gunked up.
That was the cause on my Jag, but as i said before i am new to Volvo.