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

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.

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).

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

Check under the dash for a small 80 amp strip fuse.

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

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

on W123's is it mounted on the firewall behind the brake pedal.

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

oh god:(

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.

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:

http://www.peachparts.com/shopforum/showthread.php?t=178024&highlight=gorilla

Don't beat me too hard. I only paid $500. for it and did I mention rust? :rolleyes: 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.

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.

No such luck. It's not there either.

Thanks for the help though.

Have you looked into the glow contacts in the gorilla knob as mentioned in the thread I linked?

One way to start your 220D
 

I purchased a '74 240D with non functioning gorilla knob system. (The PO had taken a hammer to the dash in anger when the steering lock locked while driving- I know - it did not fix the problem. But it allowed me to get a car with excellent tires, a great motor and manual trans for $200.)

The car was trailered home. In an effort to see if the motor even ran, I used one large battery and 3 jumpers. I disconnected the gorilla knob feed to the glow plugs, grounded the battery to the car, then jumped 12v to the high side of the glow plugs. I counted to 10, disconnected the feed to the glow plugs, then jumped 12v to the starter. With a spark and a click, it was running perfectly. The dash salt shaker glow plug is in series, I think, with the motor's 4, so don't connect for long, or perhaps one of the engine plugs will melt.

If your car starts easily with this, I suggest you check the dash salt shaker. You can get to it easily by pulling out the instruments. Make sure it get's 12v on the high side, that it is not open, and that you have 12v at the gorilla knob switch (high side). One of those parts is probably bad, the dash glow plug or the switch. I'd buy used for replacement, those parts are usually reliable.

'Hope this helps, Ron

Be extreeeemely careful about using 12-v on the loop plugs. They are designed to only take a fraction of that. In normal series operation, each plug including the one in the "shaker" window shares a part of the voltage drop as well as do the squiggly metal jumpers. So actual drop across one should be no more than 1.8 to 2 volts!!!!

Happy glow plug difficulty season everyone!:party2:

Party on! :vbac47679

According to my service CD, the glow indicator in the dash is taken out of the circuit when you pull the starter knob to the "start" position, to reduce the voltage drop...but the plugs still have power during cranking. So, if there is a problem with the switch contacts or an broken glow indicator, the engine will still start after a few seconds of cranking as the glow plugs come up to temperature (as it would if you forgot to wait).

While I've never checked this myself, I would imagine you could use an ohmmeter and check resistance on each terminal of the dash indicator, and also between each glow plug - i.e. one lead on the bus bar on each side of each individual plug, starting with the one closest to the firewall (with power off, of course). I would think that if one was burned out, you could tell by the resistance indicated (or lack thereof).

I made a wire jumper to bypass a bad glow plug in case of an emergency on the road...of course, not intended to use long-term as it would allow more current to the remaining 3 plugs.

Which now explains to me why the motor starts so easily, even with the glow plugs not functioning when pulling on the glow plug switch.

I didn't realize the gorilla switch would also engage the glow plugs. This is not outlined in the Chilton schematic. I never should have banked entirely on one of those manuals to be completely correct. Never have been in the past, why should now be any different.

Tomorrow I will pull the instrument cluster and check it out at the salt shaker and at the gorilla switch. I will also be checking at the #4 glow plug while some tries starting the motor to see if there is voltage then.

To me there is no sense in checking out any of the glow plugs until I get and or confirm any power out to #4 first. Which has yet to occur.

Thank you Katja for your additional insight!

I believe one of my next steps will be to get an OE cd for this vehicle so I can stop wasting time with nonsense.

Any recommendations? I have briefly looked at the mercedes web site to find that there are several choices ranging from about $20.00 to about $60.

Kerry,

No, I have not had the time yet.:mad: The skeeters are winning around here at the moment. I tried to get into it last night, but had troubles staying on the ground.:eek: One would think I was in Wisconsin again. As I recall that is the state bird there. :D

I will have some time tomorrow to look deeper into it. Instrument cluster will be coming out and I will be replacing bulbs there, checking the dimmer rheostat, the shaker & the gorilla switch all at once.

Thanks to all of you for your assistance and insight. I am sure I will get the answers that I need tomorrow with all the information you folks have armed me with.:)

I will keep you posted.

Thanks again,
Rick

Thanks Ron,

Such great information from an awesome group of people!

I have a feeling this problem will be solved in no time.

Thanks again,
Rick

OK, here's the latest. The glow plugs are working. The gorilla switch is working. Yay. I am a bit confused though. I have been told by the dealer that the switch on the console is for the glow plugs, too. It does not light them up. No problem. I will just fire up off of the gorilla switch for now until I get the MB CD service repair manual to further study.

Thanks for all of your help!

Rick

Really?! My 240D is as loud as a Mack truck :D

The dash indicator is the first thing in the glow plug series, if its got a bad connection, that'll stop the flow of current. Try checking for 12v on the leads of the indicator. You can unscrew the salt shaker cap and then use a small screw driver to loosen the collars for the two legs of the indicator, then the indicator pulls straight out. I'll post the wiring schematic from the CD.

The $20 cd shop manual is great. PM me your email address and I'll send you the part pertaining to the glow plugs to give you a taste of the manual.

Also, am I understanding you correctly that there are TWO knobs involved with starting your car? Mine has the one gorilla knob on the dash to the left of the steering wheel. Did you say you have another on the center console? The manual only mentions the one on the dash, even for 615 engines.

Well, good luck, and if you want that section of the manual, send me your email.

http://www.peachparts.com/shopforum/...3&d=1254351864

PM sent. My cd is on it's way, but it will be nice to take a look at a good schematic in the mean time. Thank you pizzachef. The diagram in your post is pretty much the same as the Chilton one, but much more legible and detailed.

The knob on the center console is a push / pull with a light in the middle. Oh crap, it just dawned on me that it is probably the rear window defogger / defroster. It just won't stay on. Duh. To much schematic reading too many days in a row. What a brain fart! :rolleyes:

Oh well, just another day in paradise.

Thanks everyone for all of your help and patience with a MB Diesel Noob! Hopefully, my mistakes will one day help someone else out on this message board.

Have an awesome night!

Rick

What happened to cause the glowplugs to start working?

Well Kerry,

I am almost embarrassed to say that they worked all along and I didn't realize it.:o I was mis-informed and was attempting to use the wrong switch to light off the glow plugs. I had a feeling that this diesel was starting up way too easily for 50 degree temperatures. The glow plugs were working, just not getting enough warm up time. If you look at my previous post in this thread, you will see the aha moment when I finally figure out what that other switch is actually for. Duh! I did not know that the glow plug portion was actually built into the gorilla switch even after spending days looking at the wiring diagrams. Well, yes I did, but it hadn't sunk all the way into this thick skull yet.

It was due to the information from all of you folks here and looking at a few youtube videos on cold starts along with a good nights sleep that got me the answers that my tired out brain needed.

My brain seems to keep working on things while I sleep and the answers come to me in the next day or so, normally. It was just too overloaded to get the answers the first day or two. Seventy to eighty hour work weeks for this old fart are getting to be too much these days.

I had my son operate the gorilla switch slowly tonight while I had a voltmeter on #4 glow plug. I think my face lit up brighter than the meter and the salt shaker did when it kicked on. :D

The only thing I can say is I'm glad I didn't get frustrated enough to take a hammer to it like a previous post mentioned. These MB parts are way too expensive for me to be doing things like that!:eek:

I don't understand what you were doing wrong. So you turned the glowplugs on and didn't know it?

I was using the gorilla switch to start, which actually defaults glow plugs on while starting. I just wasn't allowing any warm up time. Hence, the motor starts easier with some glow, even if minor.

I was pulling on other switch for glow, which didn't do anything other than lighting the bulb in the knob. I really feel dumb in retrospect / hindsight.

what other knob? All there is to pull is the gorilla knob and turn the key on.

Has someone rigged up something on your car?

He was pulling the defroster knob. It is a mysterious looking knob on the 115's.

Glad you figured out the problem you were having! :D
It won't be the last time you smack your forehead when something dawns on you.

those knobs!
 

Folks, I think Rick was turning on the rear window defroster thinking that it was glow plugs. (on most 220D's, it just an unlabeled pull knob next to the ash tray, that lights up when out, and does not go off automatically like later defroster controls) Then, he was pulling out the gorilla knob, quickly thru the glow plug position, and running the starter, which operates the glow plugs without the salt shaker. Then letting go of the gorilla knob, it falls back, quickly passing thru the glow plug position, to the run position for the IP. Did I get it correct Rick?

Ron

PS Rick, I had worried thoughts about telling you to pull the instruments to check voltages without warning you about the temperature gauge. It is a mechanical unit, and has a tube that goes from the gauge thru the firewall, down to the engine. Be careful not to bend or pull the tube, because you may break it open. When I pull out the instruments, I pull straight back until they just clear the dash, then pull the speedo side out about an inch, reach back and disconnect the cable. Then pull the speedo side out, so the whole cluster is about 45 degrees with dash, with temp gauge side close to the dash. Find your temp gauge tube and see how far it'll come out, and you should get enough room to get one hand into the innards of the dash for voltage checks. Otherwise, carefully remove the bulb from the engine and give the tube some slack through the firewall to get the gauge cluster out a few inches, then remove the temp gauge and oil line to get the cluster completely out. (Or remove bulb up through firewall and take out temp gauge with cluster.)

Ron,

You hit the nail on the head. Not to mention the defroster control is actually broken. It would have come to me sooner, if the switch and light actually stayed on as it should when pulled. It only stays on if you hold the switch pulled out. Release it and it goes out.

Thanks for the "heads up" on the instrument cluster. I have yet to getting around to pulling it out to replace blown out bulbs or checking out why they are not working. I have to go out of town for a few weeks, so my pet project will be on the back burner until I get back.

Thanks again to all of you for your help,
Rick