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  #1  
Old 09-27-2009, 07:41 PM
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73 220D Glow Plug Problems

This is my first post here. Sorry if it is a long post. I do have to say thanks to all of you for the vast amount of information here. It has been a great deal of help to me, a first time diesel and Mercedes owner.

I am not new to automotive. I have been ASE certified master for about as long as they have been around and have turned wrenches for 35 years for a living. I have a decent electrical background, but not much time for toys these days so I am asking for help to shorten my learning curve.

I just bought a '73 220D that was not running. It obviously has the original 79,000 miles on it, but the body has some rust problems. I had the alternator repaired by a reputable re-builder and replaced the voltage regulator while I was at it. The charging system is now working fine. One of two previous owners connected the battery cables backwards and blew all the diodes in the alternator.

I reassembled the car, checked all fluids and topped them off. I was able to start the motor and it runs great after warm up. No smoke and pretty quiet for a diesel. I drove it home without any problems. It was a warm day and it didn't take too terribly long to start it for a diesel.

After doing some researching, I discovered the glow plugs are not firing at all. I turn the key on to II position, pull out the the starter switch to the first position (left of steering wheel) and then pull the gorilla switch knob on the center console and wait while holding on the knob. The light on the switch comes on. Am I missing any steps here?

The light / indicator / pepper shaker on the dash above the steering wheel center does not light up or even get warm.

I went under the hood and checked at the rear glow plug and found no voltage there. I pulled the center console off and checked the switch and found 12v there and the same on another terminal when pulling on the switch. All of the fuses have been checked and are working fine.

From reading the wiring schematic I am able to determine that there is no fuse or relay on this system and if there is power from the switch, then even if the shaker is not functional or burned out, there should still be power going to the rear glow plug or am I missing something?

I hope someone here can shed some light as my next step will be to start tearing the dash apart and I would like to avoid that until I finish checking some other things out first.

Oh, and by the way, the dash and interior lights are not working at the moment. I am figuring the dash lights are either the bulbs burnt out or the rheostat / dimmer is bad. The rheostat does not feel right. Knob is too loose from what others in different cars feel like and the other interior lights are physically broken.

Thanks in advance for your help,

Rick

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  #2  
Old 09-27-2009, 07:51 PM
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Are you sure the gps aren't getting voltage, did you have some one hold the knob out while you check the voltage?

You are using theknob correctly right, pul it out to the first position and then pull it out just a bit more until it stops and hold for about 30 seconds. It takes a long time for those old loop plugs to heat up and for the salt shaker to glow.

Nope there is no relay, cant remember if there is a fuse or not, im sure there is one under the dash.
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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

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  #3  
Old 09-27-2009, 07:59 PM
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First find out if it still has the old loop type GP.
If it does have the loop type GP wired in series, last GP has connection to engine block then one or more GP are bad.
If it has the newer style GP wired in paralel then the salt shaker does not glow anymore check individual GP to see if it is open (no resistance).
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  #4  
Old 09-27-2009, 08:10 PM
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Confirmed, no voltage while key on and knob pulled out. Wifey did the inside while I checked and confirmed. I triple checked that she was doing everything they same way I was. I have tried preheating for several minutes, now I know why they call it a gorilla knob!

No fuse listed in the wiring diagram, as far as what the old Chilton book says anyhow. I always have taken them with a grain of salt, though.

Thanks for the quick response,

Rick

Quote:
Originally Posted by 79Mercy View Post
Are you sure the gps aren't getting voltage, did you have some one hold the knob out while you check the voltage?

You are using the knob correctly right, pull it out to the first position and then pull it out just a bit more until it stops and hold for about 30 seconds. It takes a long time for those old loop plugs to heat up and for the salt shaker to glow.

Nope there is no relay, cant remember if there is a fuse or not, im sure there is one under the dash.
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  #5  
Old 09-27-2009, 08:12 PM
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Check under the dash for a small 80 amp strip fuse.
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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg
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  #6  
Old 09-27-2009, 08:19 PM
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Confirmed, still old loop style. I know what I am talking about, thanks to all of you on this site!

I checked for voltage at the last plug in the block which is the first in the series. Nothing there at all. I figured if I found voltage there, I could solve any other problems from there in the series. The ground is good and working (I just reversed my ground on the battery to the positive and checked the ground strap for voltage with my meter) at the front of the motor which is the last in the series.

I figured there wasn't much sense in converting to the parallel fast pencil type glow plugs until the system worked first. I'm kind of quirky that way. If it works, don't fix it. If it don't then fix it the best way possible with upgrades after functionality.

Thanks for the fast reply,

Rick

Quote:
Originally Posted by Rafi View Post
First find out if it still has the old loop type GP.
If it does have the loop type GP wired in series, last GP has connection to engine block then one or more GP are bad.
If it has the newer style GP wired in paralel then the salt shaker does not glow anymore check individual GP to see if it is open (no resistance).
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  #7  
Old 09-27-2009, 08:21 PM
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Ok, I'll bite. Where abouts under the dash? General vicinity please? I am familiar with the old strip style fuses. Used to sell a lot of them!

Thanks,

Rick

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Originally Posted by 79Mercy View Post
Check under the dash for a small 80 amp strip fuse.
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  #8  
Old 09-27-2009, 08:32 PM
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on W123's is it mounted on the firewall behind the brake pedal.
__________________
1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg
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  #9  
Old 09-27-2009, 08:44 PM
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I'll take another look tomorrow after work and report back. I was looking everywhere up there earlier, pulling relays and the like, going to the 'net to identify them and putting them back in.

Gotta love the info available on the 'net today. All I have to do is type in the Mercedes part number off of the parts and do a Google search and voila, part identified! What a great way to learn a new toy!

I'm just looking to make it a daily driver and maybe later do a WVO conversion. I have friend that has the filtration equipment, so all I have to do is collect. The rest is free. We'll see how the project goes first. Some of the rust is questionable.

Thanks for your lightning fast assistance 79Mercy!

Have an awesome evening,

Rick
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  #10  
Old 09-27-2009, 08:46 PM
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Quote:
Originally Posted by Rick_MD View Post
later do a WVO conversion.
oh god
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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg
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  #11  
Old 09-27-2009, 09:18 PM
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I've never worked on the old gorilla know glowplug systems but I've read a number of threads on the topic on this forum. I don't remember anyone ever mentioning a strip fuse in that system.
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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
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1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
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  #12  
Old 09-27-2009, 09:23 PM
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I found a thread which says the gorilla knob system has no relay or fuse. This thread states that the glow plug contact in the gorilla switch can fail:

How to use the gorilla knob
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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
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  #13  
Old 09-27-2009, 09:28 PM
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Quote:
Originally Posted by 79Mercy View Post
oh god
Don't beat me too hard. I only paid $500. for it and did I mention rust? Probably more than there should be. Definitely not going to be a collector or anything. Right now it's just a rolling parts car. More inspection will tell the story when I get her up in the air to do the oil change and take a better look see. Probably going to wind up regretting buying it at all.
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  #14  
Old 09-27-2009, 09:28 PM
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200D's had a resistance coil mounted on a ceramic block in the glow plug circuit. Mounted on the firewall, I think. Not sure if 220D is the same or not.
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  #15  
Old 09-28-2009, 06:57 PM
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No such luck. It's not there either.

Thanks for the help though.


Quote:
Originally Posted by 79Mercy View Post
on W123's is it mounted on the firewall behind the brake pedal.

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