Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help

Go Back   PeachParts Mercedes-Benz Forum > Mercedes-Benz Tech Information and Support > Diesel Discussion

LinkBack Thread Tools Display Modes
Old 04-23-2010, 02:59 AM
paridah's Avatar
Registered User
Join Date: Feb 2006
Location: Clinton, MD
Posts: 49
1993 300SD W140 GlowPlug light

I am currently experiencing a glowplug light issue. The glow plug light comes on after the car is started, but does not come on when the key is in the pre-glow position. Any advice?

Reply With Quote
Old 04-23-2010, 03:16 AM
Diesel911's Avatar
Registered User
Join Date: Sep 2007
Location: Long Beach,CA
Posts: 46,195
I forgot to ask if despite the Glow Plug Light issue if your Engine is starting OK?

You have been a member a long time. If you have read any of the threads or posts on this I believe the first thing folks would say to check as the Glow Plugs themselvers as the first plasce to start.

You can go to the Diesel Giant Site and follow his pictorial with the Ohm/Volt Meter (multimeter) or you can go to the DIY section and see if we have a proceedure. His pictorial I believe is for a 123 but the method is the same.

The good thing here is you can check the Glow Plugs without removing the Intake Manifold.

If it turns out any of them are no good I would read up on removing them before I tried to do that as the long Glow Plugs in the Aluminum Heads sometimes break off in the Head when you try to remove them.

DIY Repair Links

If the Glow Plugs appear to be OK and your system has a ExternalTemp Sensor connected to your Glow Plug Relay I would suspect that.
84 300D, 82 Volvo 244Gl Diesel

Last edited by Diesel911; 04-23-2010 at 03:29 AM.
Reply With Quote
Old 04-23-2010, 03:51 AM
Diesel911's Avatar
Registered User
Join Date: Sep 2007
Location: Long Beach,CA
Posts: 46,195
I do not have the correct manual for your car but these are about later model Glow Plug Systems.

Also on the 123 Glow Plug Systems when you are cranking your starter you Glow Plug Relay is avctivated bay way of another circuit and a wire coming up from Starter Solenoid.

In the comments on how the Relay worked normal it said that the duration of the preglow is decided by the Temp Sensor inside of the relay or a Coolant Temp Sensor.

So on most 123 the temp sensor is in the relay and would determine the preglow cycle; but when I turn the key and start Cranking the Starter the preglow relay is activeted again (manually).
Attached Thumbnails
1993 300SD W140 GlowPlug light-gp-1.jpg   1993 300SD W140 GlowPlug light-gp-2.jpg  
84 300D, 82 Volvo 244Gl Diesel
Reply With Quote
Old 04-23-2010, 10:38 AM
compu_85's Avatar
Cruisin on Electric Ave.
Join Date: May 2008
Location: Springfield VA
Posts: 5,212
On the 1988+ cars this means you have a bad glow plug or two. Your car must not have come with an owner's manual, that feature of the preglow system is covered

Get out the meter and check the plugs. Thankfully you can just unplug the connection at the glow plug relay, rather then using the terminals on the plugs themselves.

Note that your relay does not have a fuse, it has a self resetting circuit breaker.


1991 350SDL. 230,000 miles (new motor @ 150,000).

Tesla Model 3. 136,000 miles. Been to 48 states!
Past: A fleet of VW TDIs.... including a V10,a Dieselgate Passat, and 2 ECOdiesels.
2014 Cadillac ELR
2013 Fiat 500E.
Reply With Quote


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

All times are GMT -4. The time now is 06:23 PM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2023, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page