No GP light this morning........but started - PeachParts Mercedes-Benz Forum

Burnzy · #1 01-14-2010, 10:24 AM

This morning I turned the key and to my dismay, no glow plug light. I waited until the relay clicked and turned the key. My car started but it was not a pretty picture. Lots of smoke and lots of shaking for about 30 seconds then all was "normal". I looked at my fuse and it appears to be OK. Where should I start? Check all the GP's? Does no light mean all the GP's are toast or just some of them? I thought I remembered reading that the light will not come on if 2 or more are not working. Is that correct? Any help would be appreciated.

Thanks

snookwhaler · #2 01-14-2010, 10:27 AM

I had this problem recently. 2 of my glow plugs were out of spec. 1.2 ohms on the meter. I replaced them and the light came back. I also had the "start up stumble". After replacing the bad plugs (autolites), she lights right off and settles into a smooth idle. No more stumble.

Only takes about 5 minutes to troubleshoot the whole system with a meter. Pretty simple.

Graplr · #3 01-14-2010, 10:43 AM

I do believe that the light will not illuminate if 2 or more are out or glow plug #1 is out.

Time to get out the old multimeter and test the resitance at the glow plugs. If you need a refresher you can check out dieselgiants write-up. I test the resitance at the GP itself though.

Brian Carlton · #4 01-14-2010, 10:44 AM

Quote:

Originally Posted by Graplr

I do believe that the light will not illuminate if 2 or more are out or glow plug #1 is out.

Agreed.

tr1cky · #5 01-14-2010, 11:16 AM

Don't rule out the integrity of the Glow Plug relay itself.

My recently acquired 300SD recieved the full glow system treatment after testing tips and instructions from PeachParts. I had no glow light due to multiple issues.

I had 3 original glow plugs that weren't doing their job
Installed 5 new Bosch glow plugs
Tested and inspected wiring
Wiring was okay
Relay/Controller was kaput
Installed new Relay

I was able to start the car every morning, down to the single digits without the aid of the relay and the car smoothed out quite rapidly considering. Now with the relay functioning properly, I'm glad that I replaced all 5 glow plugs as well rather than replacing only those that were defective.

Burnzy · #6 01-14-2010, 01:40 PM

Thanks for all the help. I borrowed my bosses meter and checked things out during my lunch break. It would appear that the number 1 plug is no longer working. I am surprised that only one glow plug failing would cause such havoc when starting the car. Is that normal?

Thanks

snookwhaler · #7 01-14-2010, 02:12 PM

Yep #1 will cause the light to go out as mentioned in post #3.

Graplr · #8 01-14-2010, 02:20 PM

Quote:

Originally Posted by Burnzy

Thanks for all the help. I borrowed my bosses meter and checked things out during my lunch break. It would appear that the number 1 plug is no longer working. I am surprised that only one glow plug failing would cause such havoc when starting the car. Is that normal?

Thanks

It can, especially in cooler temps. While you're pulling that one you might as well pull the other 4 and check for carbon on the tips. You can also hook them directly up to 12Vs and see how well they glow when they are out of the car.

mespe · #9 01-14-2010, 02:41 PM

My experience shows that once you pull a glow plug, chances are you ruined it. the electrical connection doesn't take much torque.

snookwhaler · #10 01-14-2010, 03:21 PM

Quote:

Originally Posted by mespe

My experience shows that once you pull a glow plug, chances are you ruined it. the electrical connection doesn't take much torque.

+ 1 on that. When I removed both of the autolites the shaft broke and spun. I actually had to use Needle nose Vice Grips to secure the shaft (behind the nut) and then remove the little nut in order to remove the wire.

#11 01-14-2010, 04:31 PM

Quote:

Originally Posted by Burnzy

Thanks for all the help. I borrowed my bosses meter and checked things out during my lunch break. It would appear that the number 1 plug is no longer working. I am surprised that only one glow plug failing would cause such havoc when starting the car. Is that normal?

Thanks

Yup, one GP can make it hard to start; just replace the bad one, you should get your light back and it should start correctly. I replaced my #1 GP earlier this week, same story.

Graplr · #12 01-15-2010, 10:06 AM

Quote:

Originally Posted by mespe

My experience shows that once you pull a glow plug, chances are you ruined it. the electrical connection doesn't take much torque.

I've never experienced that.

I have only used Bosch GPs, snookwhaler mentions Autolites...perhaps that has something to do with it??

Hit Man X · #13 01-15-2010, 10:48 AM

Quote:

Originally Posted by Brian Carlton

Agreed.

I was under the impression that was a 603 only feature? Or am I confusing that with the light that comes on again after some driving alerting you to GP failure?

#14 01-15-2010, 11:01 AM

Quote:

Originally Posted by Hit Man X

I was under the impression that was a 603 only feature? Or am I confusing that with the light that comes on again after some driving alerting you to GP failure?

My 300D 617 will also fail to light if the #1 GP is bad (it happened this week). The loss of any other 2 GPs will also cause the light to stay off. I do not believe the light coming on while driving is expected behavior.

Graplr · #15 01-15-2010, 11:55 AM

Quote:

Originally Posted by Hit Man X

I was under the impression that was a 603 only feature? Or am I confusing that with the light that comes on again after some driving alerting you to GP failure?

I'm also pretty sure this is true of the 617s. I have no idea on how it works on the 603s. I had my glow plug light come on last year while driving. I deduced that it was the GP relay. Replaced the relay with a new one and it has not come back on while driving since.

EDIT: By come on, I meant flicker on and off a few times.