Help diagnosing glow plugs - PeachParts Mercedes-Benz Forum

babymog · #1 10-16-2010, 10:32 PM

Did you try the 45 second glow yet? If not, please stop wasting forum bandwidth.

You've posted that you try to start it after the light goes off, and that the light goes off at no more than 5 seconds, you're not glowing long enough for a cold engine.

Try this, and report back.

Also, reading your post it is difficult to discern whether you understand the pre-glow, seems like you might also be cranking your car immediately and not waiting for the glow light to go off (3rd paragraph in first post). Please clarify.

Key to position 2, glow-light on, wait 30seconds, turn to start position / crank, see if it starts normally. Report results.

If this changes the starting behaviour of your engine, then we have something to troubleshoot. If you want to pull parts and see the pretty glow, have at it.

turbo97se · #2 10-16-2010, 10:58 PM

I did not understand before about this. I did after reading you post. In the past I had thought that when the glow light went out that it was done with the glowplugs and so as I had mentioned, I cycled the key 6-8 times (essentially giving 30-40 seconds of glow plug warm up). I have indeed tried leaving it for longer but it just seems like when it does start, it's still cold. It shudders until warm almost like it is missing (not firing on all cylinders).

Quote:

Originally Posted by babymog

Did you try the 45 second glow yet? If not, please stop wasting forum bandwidth.

You've posted that you try to start it after the light goes off, and that the light goes off at no more than 5 seconds, you're not glowing long enough for a cold engine.

Try this, and report back.

Also, reading your post it is difficult to discern whether you understand the pre-glow, seems like you might also be cranking your car immediately and not waiting for the glow light to go off (3rd paragraph in first post). Please clarify.

Key to position 2, glow-light on, wait 30seconds, turn to start position / crank, see if it starts normally. Report results.

If this changes the starting behaviour of your engine, then we have something to troubleshoot. If you want to pull parts and see the pretty glow, have at it.

babymog · #3 10-17-2010, 08:49 PM

Quote:

Originally Posted by turbo97se

I did not understand before about this. I did after reading you post. In the past I had thought that when the glow light went out that it was done with the glowplugs and so as I had mentioned, I cycled the key 6-8 times (essentially giving 30-40 seconds of glow plug warm up). I have indeed tried leaving it for longer but it just seems like when it does start, it's still cold. It shudders until warm almost like it is missing (not firing on all cylinders).

I understand that your cumulative glow time might be 30-40 seconds, but that is significantly different from a 30-40 second glow, which is why I suggested it.

Good luck, any change in symptoms please post.

turbo97se · #4 10-18-2010, 11:17 PM

Had a couple of unusually warm days the past few days so nothing to report earlier. Today got a little colder so I tried just waiting for the full 40 -45 seconds until I could hear the relay click, it does indeed make a difference. Thank you for scolding me not to waste bandwidth or I would have missed the difference between the glow plug light and actual glow plug relay time! LOL

. Clearly there is something wrong with the glow plug indicator timer for the bulb in the cluster, but at least the glow plugs stay on! As the days get colder, I will know for sure!

Quote:

Originally Posted by babymog

I understand that your cumulative glow time might be 30-40 seconds, but that is significantly different from a 30-40 second glow, which is why I suggested it.

Good luck, any change in symptoms please post.

micalk · #5 10-19-2010, 08:42 AM

In another similar thread, someone suggested checking the temp sensor that is the input to the GP relay. You might give that a try and see if it extends the GP dash light.