Interesting glow plug issue

I have had some small issues with getting my car to start a few times this winter. (its not ever winter here in Phoenix but as close as it gets) If it froze overnight the glow plugs would come on for a couple seconds (4 seconds was the longest I recall) and the car would start right up. If it was in the high 30's to 40's it would not activate the glow plugs and it would crank a bit before firing. Only happened a few times. As I understand it the glow plugs run off of coolant temperature and come on at 40 degrees or below so this seemed in line to me. This past weekend I took a trip up north where the temperature got to around 30 at night but was 60's all day. The glow plugs came on for long periods of time (10 seconds or more) at every start hot or cold. Had the car at operating temperature (190 on the gauge) shut the car off and went to start it back up and the glow plug light stayed on for 10 seconds. This morning when I went to work (at home) the light did not stay on at all. Can altitude affect this? Its 7 thousand feet difference from here to there. Or maybe the light was telling me something else not related to the glow plugs?? Thanks!

Aaron

You answered your own question. Altitude plays a huge role in the glow duration.

Just did a search for "glow plugs altitude" and found more info. Thanks for the point in the right direction. Thought my car was just crazy. Is there any way to artificially influence the system to get the glow plugs to stay on longer in the winter? I read you can unplug the temp sensor and it will assume its very cold and give you full glow plug time but I would rather do it without popping the hood every morning. Maybe a setting I can change with vcds?

I have read threads that say you can adjust glow duration somewhat with VCDS. Time for more searching unless someone has a link.

SOOT4BRAINS said:

Just did a search for "glow plugs altitude" and found more info. Thanks for the point in the right direction. Thought my car was just crazy. Is there any way to artificially influence the system to get the glow plugs to stay on longer in the winter? I read you can unplug the temp sensor and it will assume its very cold and give you full glow plug time but I would rather do it without popping the hood every morning. Maybe a setting I can change with vcds?

Click to expand...

There's no need to. A properly running TDI should have more than enough glow time from the factory.

I guess I don't really need longer glow plug time, I just need to change at what temperature they come on at a little bit. Only mornings when its about 35-45 degrees is when it gives me trouble. At my altitude (1200) even when its below freezing they come on for 2-3 seconds max. An adjustment to the barometer would be ideal, maybe fool it 2000 feet or so. The best it has ever started was on my trip when it froze overnight. Glow plugs came on for 10 seconds or so and it fired effortlessly.

Glow it twice when cold and your starts will be quicker and cleaner. Hope this helps.

It was 46F this morning when I went to start my Golf and the GP's did come on and stayed on for almost a full 4 minutes. The pre-glow should be ~ 23 seconds regardless of the GP light, so I would count to 15 and then try starting.