glow plugs '76 240D - PeachParts Mercedes-Benz Forum

abracadabra · #1 10-04-2009, 02:51 PM

I've done the search for glow plug replacement procedure and got so many hits, and after pages of checking I couldn't find what I needed for my particular rig.

Basically I've got really old tired plugs, the engine starts terribly in the morning especially now that the temp has dropped. I've been putting off this for some time...

Its a '76 240D with gorilla knob in the dash.

I've never done this before and the only procedures I find are for newer cars which is not what I've got!

Any links to the procedure for the old diesel engines would be awesome!!

mark in Portland

kerry · #2 10-04-2009, 03:20 PM

You should be able to replace the old style series plugs with pencil plugs which are a far superior glowplug. I think dieselgiant sells the kit but you could also buy the replacement plugs individually and just make up your own jumper wires. Buy the plugs, install them in engine, throw away (or store) your heavy loop wires, put the 12v hot wire to the first plug near the fireall. Use jumper wires to the other three plugs and throw away (or store) the ground wire from the plug nearest the radiator.
The retrofit pencil plugs are different than the later pencil plugs because they have the larger threads of the loop plugs. A search on here should reveal the part number for the retrofit pencil plugs.

Diesel911 · #3 10-04-2009, 03:57 PM

I have not read of any particular problems removing or installing the Origional Glow Plugs with the exception of the wiring.
If you decide to keep your origional style of Glow Plugs take some good pics or draw a good diagram as to where the wires go so they can go back to the origional position.

This might help narrow future searcnes;DIY Links
http://www.peachparts.com/shopforum/diy-links-parts-category/

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

abracadabra · #4 10-04-2009, 05:39 PM

Well I've read about the pencil plugs but honestly I've had zero problems for the last 7 years with the original plugs so I'd rather just stick with them.

I guess what I wonder, on the older system, do I just remove the old plugs one at a time and thread the new ones in, and thats it?

mark

79Mercy · #5 10-04-2009, 05:46 PM

yep that is, but make sure you get the wires installed correctly. I'd take some pics before you stat taking it apart so you know how it all goes back together.

kerry · #6 10-04-2009, 06:00 PM

Quote:

Originally Posted by abracadabra

Well I've read about the pencil plugs but honestly I've had zero problems for the last 7 years with the original plugs so I'd rather just stick with them.

I guess what I wonder, on the older system, do I just remove the old plugs one at a time and thread the new ones in, and thats it?

mark

Don't know how cold it gets where you are, but once you switch to pencil plugs in cold weather, you would never go back. It added at least 10 degrees to the lowest temperature at which my 77 300d would start. I'm guessing it would greatly reduce your muscle strength by allowing much shorter pulls on the gorilla knob.

abracadabra · #7 10-04-2009, 06:39 PM

Well it rarely gets below freezing here, but last winter it got into the 20's and this car was the only one out of the 3 I had that started!

mark

kerry · #8 10-04-2009, 07:09 PM

I'm obviously not doing a very good job of convincing you to switch. I'll add one more benefit. If one loop plug fails, they all fail, Not so with pencil. You'll still have 3 functioning plugs.

gerkebi · #9 10-04-2009, 07:30 PM

I have a '75 240 D and I stayed with the loops. I got them at the dealer, not too expensive, and they were a snap to replace. The only slightly tricky part is keeping the wires from rotating as you take off the nut at the top. Other than that, pretty straight forward.

Next time around I may try the pencil plugs based on kerry's comments.

79Mercy · #10 10-04-2009, 07:36 PM

I want to upgrade my plugs to pencil style in my 1976 300D. 45 seconds when cold is to long to wait for the light to go off.

abracadabra · #11 10-09-2009, 02:16 PM

Okay so I can get the old style plugs locally for just under $25 a pop.

I'm real tight on money right now though, and I wonder does it make sense to just replace the bad plug/s, instead of all of them?

And, what's the best way to figure out which plug is bad, with an ohm meter? I've seen some procedures on the newer style but not much info on checking out the old plugs, can anyone help here? Its just getting harder and harder to start and if I can save on some $$ right now it would be really good!

mark in Portland

79Mercy · #12 10-09-2009, 04:36 PM

Thats a lot for glow plugs. search around online and you can find them for about 8.24 each.

Diesel911 · #13 10-09-2009, 04:55 PM

Quote:

Originally Posted by abracadabra

Okay so I can get the old style plugs locally for just under $25 a pop.

I'm real tight on money right now though, and I wonder does it make sense to just replace the bad plug/s, instead of all of them?

And, what's the best way to figure out which plug is bad, with an ohm meter? I've seen some procedures on the newer style but not much info on checking out the old plugs, can anyone help here? Its just getting harder and harder to start and if I can save on some $$ right now it would be really good!

mark in Portland

Because of the way the wires are set up you might have to remove the wires to Ohm them.
I would just take the next step and pull them all and have a look; If you pull them out often you can see that the Loop is burnt through.

Codifex Maximus · #14 10-09-2009, 05:23 PM

Quote:

Originally Posted by abracadabra

I'm real tight on money right now though, and I wonder does it make sense to just replace the bad plug/s, instead of all of them?

And, what's the best way to figure out which plug is bad, with an ohm meter? I've seen some procedures on the newer style but not much info on checking out the old plugs, can anyone help here? Its just getting harder and harder to start and if I can save on some $$ right now it would be really good!

mark in Portland

If I remember correctly, the old style plugs are setup as a series circuit. One break in the series, either a bad glow plug or a break in the wiring, and the whole circuit is down.
That is why it is better to go to the new style plugs which are parallel circuit wired; one plug goes out and the others still work.

Codifex
1981 240D SkyBlue
1983 300DTurbo w/sunroof

kerry · #15 10-09-2009, 05:30 PM

If you're really hard up and only one plug is bad, just jump it with a really heavy gauge wire and the rest will work. Or, put the bad one in the hole nearest the front and hook up the front ground wire directly to the second plug back. Three plugs is better than none.