[yk58]

Hello, everybody!
I have a 2002 Jetta Tdi and when I turn the ignition key, the glow plugs do not get energized. They do get energized but only after the engine has started. I changed the coolant temperature sensor and the glow plug relay; however, the problem still exists. Any suggestions would be appreciated.
Thank you!

 

[chittychittybangbang]

What error codes do you have?

 

[yk58]

Sorry for the delay. There are no error codes. However, the problem still persists.

 

[chittychittybangbang]

If it were a wiring harness problem it should throw an error code. How do you know they aren't energized before and only after the engine starts?

 

[yk58]

Thank you for the fast response. I pierced a hole in every one of the glow plugs wires, connected a multi-meter and measured the voltage.

 

[chittychittybangbang]

Just to repeat something in another GP problem post today, when the ambient temp is above 48oF they do not light before starting the engine. They do light after every engine start below 2500 rpm. Despite references in official literature about the pre engine start glow starting when you open the driver's side door, no TDI has ever had this.

 

[Keithuk]

They do light after every engine start below 2500 rpm.

That sounds a bit strange chitty every engine start will be less than 2500 rpm isn't it?

 

[chittychittybangbang]

Sorry, what I mean is that after every engine start the glow plugs will be on. They stay on for a while unless the engine rpm is higher than 2500 rpm. On the older cars you could hear a relay clicking whenever the rpm when over that.

 

[Keithuk]

Ok but mine doesn't work like that. Depending on temperature you turn the ignition on and the glow plug warning light shows for a few secconds then goes off. You crank the engine and it starts. I doesn't continue glowing after the engine has started even at less than 2500 rpm.

 

[chittychittybangbang]

Ah, I understand now, you're talking about the glow plug light. I'm talking about the glow plugs in the engine. I'm not sure about the GTD or UK models because they have different emissions. At least in North America, every TDI runs the glow plugs after the engine starts regardless of temperature. This lowers emissions and hastens warm up which lowers engine wear and noise.

 

[Keithuk]

Yes in the UK we've had diesels for many years that the glow plugs continue glowing after the engine has started to reduce white smoke and emissions but the dash warning light is also lit.

Glowplug

In some newer cars, glow plugs continue to operate for up to 180 seconds after engine start to keep the engine within emissions regulations, as combustion efficiency is greatly reduced when the engine is very cold.

 

[yk58]

Thank you very much for your detailed explanation! It is greatly appreciated!