all 5 glow plugs burned out!!! 1983 300D - PeachParts Mercedes-Benz Forum

funola · #1 01-04-2011, 11:23 AM

I thought I'd have many trouble free miles by installing 5 new Bosch Duraterm glow plugs back in August of this year. Engine has been starting up fine util last night, when I noticed the glow plug light did not come on. I checked it with my inductive ammeter this morning and it drew zero current! Took out the ohmmeter and checked all glow plug resistance and they were all open circuit! It is unbelievable they failed together in such a short period of time! Any theories as to why? I will check the glow relay to make sure it is not 'after glowing'. I will put the old glow plugs back in for now.

Anyone else have problems with Bosch Duraterms? I thought they were suppose to last much longer with its new 'dual coil' design? Maybe not?

thayer · #2 01-04-2011, 11:32 AM

mine have been afterglowing forever and in the 3 years I've owned the car I have replaced one plug.

I assume that gargantuan fuse would blow before it drew enough current to fry all the plugs, but considering they all blew at once, it would have to be too much current draw.

Diesel911 · #3 01-04-2011, 11:33 AM

If you bought the Glow Plugs from the same place it could simply be you got a bad batch of Plugs. I have read of even Bosch Glow Plugs new out of the Box being dead on arrival.
Are the Bosch made in Germany or France or are they Bosch India?

In general worn out Injector Nozzles that causes a bad spray pattern and not Reaming the Carbon out of the Glow Plug can shorten the life of the Glow Plugs.

Far fetched but what if for some reason it is the Wiring Harness full of broken or burned wires. Use you Ohm Meter and put the Probe on the Terminal end of the Glow Plugs to see if it is actually the Glow Plugs themselves that have an open circuit.

The other part of the circuit would be the Ground; is there any problems with the Engine Ground Strap?

75Sv1 · #4 01-04-2011, 12:08 PM

I'd also pull one of the GPs. Then test it outside of the engine. I used a battery charger. Clamp one of the leads to the end terminal and the other to the body. The GP should glow with power on. I had problem with my Ohmmeter when the GPs wre in the vehicle.
I also agree, that the Relay box and other wireing needs to be checked.
Tom

pawoSD · #5 01-04-2011, 12:17 PM

Sounds very odd....I've had a set of Duraterms in my car for almost 3.5 years now with not one failure....and it afterglows for 3 mins every time. In fact, out of all 4 of our diesels with the duraterm plugs.....we've had only one fail in the past 3 years.

mespe · #6 01-04-2011, 12:19 PM

Overly aggresive tightening of the electrical connection of the GP (or removing a GP) causes problems.

oldsinner111 · #7 01-04-2011, 01:27 PM

I run alternate fuels so I replace GPs every 6 months.No big deal,cost little compared to free fuel.

Jeremy5848 · #8 01-04-2011, 01:38 PM

If the preglow relay stays on all the time it will burn out anything, even a Duraterm. That would be my first thing to check.

ah-kay · #9 01-04-2011, 02:08 PM

Quote:

Originally Posted by oldsinner111

I run alternate fuels so I replace GPs every 6 months.No big deal,cost little compared to free fuel.

What is the rationale when using alternate fuels? I do not replace them unless they are bad.

pawoSD · #10 01-04-2011, 02:18 PM

Quote:

Originally Posted by ah-kay

What is the rationale when using alternate fuels? I do not replace them unless they are bad.

They are probably destroyed a lot faster by the veg slop getting all over them. Sounds like that engine lives a hard life, excessive boost....K&N dirt intake....wshew.

scottmcphee · #11 01-04-2011, 03:20 PM

Quote:

Originally Posted by oldsinner111

I run alternate fuels so I replace GPs every 6 months.No big deal,cost little compared to free fuel.

Instead of chucking your old ones, send them my way!

oldsinner111 · #12 01-04-2011, 05:27 PM

They are dead.

funola · #13 01-04-2011, 05:45 PM

Quote:

Originally Posted by scottmcphee

Instead of chucking your old ones, send them my way!

Hey this is my thread! Send them to me!

All glow plugs are fine! I screwed up the measurement with the ohmeter. I used the ohmeter alligator clip lead and shoved it into the glow plug harness connector terminals thinking it made contact but in fact no contact was made. I should have put the ohmeter lead on the glow plugs next but I didn't. What threw me off was I heard the relay click as I turned the key and thought the glow relay was working. After taking the cover off the the relay I saw that the relay click was momentary (1/4 of a sec) so the glow plugs never got voltage.

I didn't have another relay so decided to make it manually controlled. I took a pic in case anyone wants to do this to theirs.

I unsoldered the upper relay coil connection from the PC board and wired a momentary push button switch to it (long wire on the right). It needs +12 to pull the relay in to supply power to the glow plugs. I also unsoldered the glow plug light terminal ( terminal #3 on the 4 pin connector) from the PC board and soldered it to the glow plug relay so the light comes on whenever there's power to the glow plugs (short wire on the left. I unsoldered from the PC board since I do not know if not unsoldering them will do any damage to the electronic circuitry. The push button is mounted under the head light switch , which I took constant +12 V from also.

Works great! I don't have to worry about the glow plug relay flaking out on me again I hope.

Ps, don't forget to disconnect the battery + terminal when you work on the glow plug relay because it has constant +12V on it!

layback40 · #14 01-04-2011, 09:04 PM

Hey Fun,
Have you pulled them yet? Would be interesting to see the surface of them. You may have had some high acid WVO that quickly killed them. Its only speculation until you examine the surface for pitting. Failing that or mespe's good suggestion, if you tug on the connection hard enough it will come out!!

Maybe the diesel gods have just sent you a message !!

funola · #15 01-04-2011, 10:16 PM

Quote:

Originally Posted by layback40

Hey Fun,
Have you pulled them yet? Would be interesting to see the surface of them. You may have had some high acid WVO that quickly killed them. Its only speculation until you examine the surface for pitting. Failing that or mespe's good suggestion, if you tug on the connection hard enough it will come out!!

Maybe the diesel gods have just sent you a message !!

Sorry to disappoint you but the glow plugs are all fine and looked beautiful with just a light coat of dry carbon at the tips. I did pull them, and decided to hook them up to a battery and they all glowed, that's when I realized I screwed up with the ohmeter test. Acid WVO? I doubt it, my WVO is very clean, my VO filter never clogs and has a lower vacuum reading than when on diesel!