My glow plugs only last for about a month before they burn out. Anyone run into this problem?

 

Hey, AK, Sorry I can't help you with the glow plug question, but I've got an 81 300D with a heater control valve problem. I just found this forum a few days ago, and to be honest, from the number of replies in comparison with the number of readers of the posts, I don't think we're going to get too much help here! I'm heading to greener forums. My MG forum beats this one all to heck! I hope there's a better MB forum on the web! This one is sad!

 

in 1981-1983 the 240d used a m616 diesel engine its a simple circuit consisting of 5 glow plugs , 1 indicator lamp (in dash), preglow time relay which is wired to batt /grd/ sw, and glow plugs i need some more info inorder to help you i have a few test you can run . youll need a simple voltmeter with a min 20 amp rating for current draw . locate the preglow time relay (should be mounted driverside , fender just behind headlight i think a little black box at least for an 300sdl 1987 it is ) unplug the 5 pin conn. to the relay (the large bulky connn.).with your volt meter set to OHMS put one lead to ground and the other to each pin in the conn. 1-4 or 5 if got 5 cyl. record # of each if you get 1 ohm or less bad preglow time relay if get (o.l) open reading a.k.a infinity , bad glow plug or wiring to glow plugs / ANOTHER TEST !! turn ign. sw to 2 position(pre-glow) the light bulb rt of kombi should be lit , with v. meter measure voltage at 80amp fuse (inside the cover of pre-glow time relay ) if you get 0v. open circuit between fuse and batt. or bad fuse . 12v = defective preglow time relay . then LASTLY!chek the resistance of wiring harness to glow plugs from preglow relay for shorts or opens bend and move the harness when doing so

 

Thanks West, I'll try those tests. When I pull the old plugs out, they are always flattened on one side of the tip. Is this normal? I'm thinking maybe I have alot of carbon build up in there and need to ream it out.
Anyone know where I can get the reamer tool.?

 

Am new to this forum and MB, but hve been into a couple of diesel engines. My reply is based generally on minute knowledge of mechanical things.
From your description, It would appear that the glow plugs are literally being hammered by the piston top or something on top of them-such as buildup as you state. My experience with glow plugs has been either they work or they don't. (Either drawing current or "open", no current.) The combustion chamber (fire deck) clearance ,as the books call it is reduced to a very small diameter and wrong plug with incorrect "reach" (depth) seating could put it in harms way. Also, some plugs use a ring between head and plug to reduce temps. Most engine designs I am aware of, are either "prechamber" (a small pocket in which the plug is mounted to allow combustion process to begin, or "direct" (with plug mounted very close to piston at TDC.
So, to restate, check to see if wrong plugs, or if they use a "ring" betwen head and each plug. If that does not correct,, drive it hard (after warming up) for couple minutes to break up build up on piston tops. Am hesitant to recommend next step.
BTW, has the head been removed for work sometime in past, prior to the problem. The reason for asking is, on some engines, fire deck clearance is determinded by that thickness of head gasket. Cute, Huh.
As always, no warranty is implied, either stated or written.
Now maybe someone with respond to my question posted in another area.
Hope this works for you.
Tom

 

Disreguard my last!!
Oldtimers setting in. I was mixing injectors and glow plugs in my reply!
In your question concerning flattened plug, does the plug appear physically moved, or just "burned" off. If the plug appears physically "bent" by mcehanical means, buildup does apply as mentioned in my previous. However, if appears
"burnt" off that is usually caused by incorrect fuel dispersal-ie, dripping injector (s) It is unusual that "all injectors " would be leaking unless it has been long time since replacing.

I know of no glow plug that uses a ring between plug and head. Sorry, about the miscue. Guess that why I wear a namtag when going to parties, so I know who I am.
BTW, have found that rebuilt injector (nozzle) work as well as new for me.
Tom

 

Thanks, Tom. I don't know the history of the vehicle; I've just had it since august. It's very possible that it has the original injectors. The flattened glow plugs appear to be burned off rather than bent or smashed. It sounds like I need to replace the injectors and ream out the glow plug ports for starters... Thanks for your input.

Andy

 

Am not quite sure what you mean by reaming out, but would not remove any metal anywhere!

Retro Tom