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W211 OM642 new glow plugs malfunctioning.


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In recent months, the glow plug indicator has remained illuminated post-startup, necessitating the replacement of a glow plug each time, as indicated by my previous Foxwell scanner. In total, I replaced three glow plugs over a span of six weeks, which resolved the issues. I utilised some old glow plugs when necessary, intending to acquire new ones subsequently.
Ultimately, I procured new glow plugs, and during installation of the Beru components, cylinder 5 exhibited an open circuit, which was concerning. I changed it, and all functioned properly. Subsequently, cylinder 1 also went open circuit; I replaced it as well, and everything is now functioning correctly.
Is there an underlying issue causing my glow plugs to fail, or are the new glow plugs defective? Additionally, I experienced this problem prior to installing the new glow plugs.

It is noteworthy that each instance the scanner has indicated a glow plug, it has consistently been the case that the glow plug has failed due to an open circuit.
I am aware that glow plug relays might malfunction, although I am not receiving any failure codes for the relay. I would appreciate the insights of our OM642 experts. Thank you in advance.

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It is peculiar that they are exhibiting an open circuit; typically, resistance increases as they deteriorate. The standard resistance measured between the glowplug tip and the adjacent head should be approximately 2 ohms; upon failure, this often increases to around 40 to 60 ohms.
Failed one.

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You indicate that the issue occurred prior to the installation of the new plugs; hence, I would examine the glow plug relay, since it appears the timer within the relay may be malfunctioning, causing it to remain activated and then damaging the glow plug by failing to deactivate.

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The glowplug circuit is protected by a 225 Amp fuse; therefore, if the relay were to malfunction and all six plugs remained continuously on, I anticipate there would be additional complications.

An open circuit may indicate a connector or wiring issue that is temporarily resolved by replacing the plug. Have you evaluated the plugs you have extracted?

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Are there two types of glow plugs in our engine? Some are 4.5 volts, while others are 12 volts.
Do you currently possess several types of plugs for the engine? I am uncertain if this would have any impact.
If you have never replaced the GP relay, it does not have an indefinite lifespan.

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I apologise for the delayed response; however, I encountered another problem with the vehicle following the replacement of the glow plug. It was determined that the exhaust back pressure sensor was causing the car to exhibit various erratic behaviours. I tested the plugs after removal, and they exhibited an open circuit. I considered the possibility of the relay being defective and still suspect that may be the cause.
I possess all the beru components except for a few reliable older ones, and everything appears to be functioning well currently. I replaced the relay approximately three years ago; however, if they continue to fail, I will seek a new relay.
 

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