Hi, i live in the Indianapolis area and just bought a 1978 300D.
I am from Germany and live over here since more than 6 yrs. now.

Finally i wanted to get an old Merc. Diesel again (like in the good old times back then while i was driving a 190 Diesel, the best car i've ever owned).

Bought the Tank on Friday, drove home and it didn't start anymore after i've shut it off. The problem was easy, the battery didn't charge, caused by two weak, corroded soldering points at the voltage regulator.

So, after this was fixed, i drove the car around, no problem whatsoever, shut it off on Sunday afternoon and it didn't start anymore after that.

Glow plug indicator light didn't work so i did some research and found the problem:

a bad glow plug.

Today i installed 5 new glow plugs (loop style) the glow plug indicator light came on for 2 seconds and immediately 2 GP's burned out.

I checked everything and thought perhaps i connected something wrong, i installed some of the old good plugs again, no GP indicator light, but the car sounds like it wants to start, and in this second when it sounds like the engine would start, the indicartor light starts flickering ??

Any idea ???


Thanks and HELLO from Indy !!!

What brand of glows did you install?

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

Do the loop glow plugs need to be wired in series? If you lost two plugs, it sounds like you wired them in parallel

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85 Merc 300D - Unwinding 31 years of wear
86 VW TD
Mahindra Diesel
Iseki Diesel

In 2007 I didn't own a diesel.

Show us a picture of how you have the loop plugs wired. I suspect that there's an insulator misplaced taking a couple of plugs out of the system and the excessive current in the plugs properly wired, burned them out.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Thanks for the quick responses, i have wired them in series (original) i will take a picture as soon as i get home tonight after work, the brand of the new ones is "Autolite" from O'reillys.

If an insulator is in a wrong position the current will bypass that plug, increasing current in the remaining plugs.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

Is there a pictures somewhere in the forum which shows the correct insulator placement ?

Probably. The key is that the incoming wire and the outgoing wire cannot touch each other. The insulator forces the current to pass thru the glowplug loop.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

There is better udated Glow Pluge that you can use to replace the Older Style Loop Glow Plugs. However, they are wired differently.

You should only need the parts circled in the Picture. The Wires you can make yourself. The Bosch 80035 updated Glow Plugs can be bought individually from our Sponser of other paces.

Instructions on installation are found in the below Threads. Be sure to note that not only is the wiring different that the Wire that grounds the the original Glow Plugs is not used
DIY Repair Links
http://www.peachparts.com/shopforum/forumdisplay.php?f=82

http://www.peachparts.com/Wikka/DoItYourSelf

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84 300D, 82 Volvo 244Gl Diesel

Here are the pictures of the glow plugs:

is the insulator attachment right?

I can't really tell but there's definitely something different about the third plug from the firewall. It's lacking something.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

yepp, this plug looked different than the other ones but it's brand new. The insulator doesn't have the metal cap.... ...i don't know....

I've ordered the pen style Bosch 80035 form advance auto parts tonight and i am going to wire them parallel.

The Resistance Wire (in the Red Circle) is grounded on the Sensor in one of the Pictures; it should not be touching anything but the Glow Plugs.

That would quickly burn at least one of the Glow Plugs or the Fuse.

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84 300D, 82 Volvo 244Gl Diesel

When you install the New Adapter Glow Plugs be sure there is an 80 amp fuse in the system.
You can use the Factory 80 amp strip Fuse that goes on the Fire Wall in that Plastic Box or one you add to the Circuit.

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84 300D, 82 Volvo 244Gl Diesel