1976 300D location of glow plug fuse and timer relay?
 

Hello does any one out there have a quick description of where the glow plug fuse would be located on a 1976 300d? The glow plug timer relay?, It is not the newer style that is on the fender with the plug connections
Thanks
mercedes hawker

It does not have one
 

It does not have one unless some one upgraded the type of glow plugs. If you have, a solid, un-insulated wire shaped like a W running from glow plug to glow plug. The pull start (gorilla knob) turns the plugs on and off you look at the salt shaker a little round thingy to the left of the steering wheel until it glows red then pull the start handle all the way out to crank the engine. The disadvantage of these older glow plugs is if one plug dies they all fail to work and the salt shaker on the dash that glows red when the plugs are hot is actually a glow plug in there glowing red if it burns out you are really screwed. What is it you are trying to do?
Dave S

thanks for your reply still looking though
 

hello thanks for your reply. This 300D has a key start and stop. NO knobs to pull. Turn the key on and let it sit a second ( only light is the red alternator light) then try and start ( cold nothing , a little tiny shot of starter fluid and it starts up fine and idles fine. Turn it off and it starts back up. just not cold starting. I have a haynes manual but the closest Wiring diagram I can find is a 1977 300d and it show a 50 amp fuse in line with the glowplugs down line from the timer relay.
any more help is appreciated
thanks
mercedes hawker

Upgaded?
 

Sorry then that is how my 1976 W115 is and I thought all were that way a lot of people have converted there’s to the newer style glow plugs eliminating the long wait for warm up and eliminating the gorilla knob completely. There is a thread some one just started asking a similar question http://www.peachparts.com/shopforum/diesel-discussion/149106-mix-n-match-glowplug-relay.html
In it some one states Mercedes used the old glow plugs like I described until 1981 so maybe some one has upgraded your car to the pencil style plugs using that as a search word may come up with something helpful.
Dave S

Is this 300D a w123? If so its got the old loop style plugs and the fuse is a strip of metal in rubber box on the firewall where the GP wire comes from. You can fake this fuse using a cut up aluminum can. Dealership sells the fuse for about $1.89. The relay will be a larger rubber box on the driver's side fender well. And if loop plugs burn out its really obvious, the loops will be severed like burnt out light bulb filaments.

Still looking.
 

I am going to call this a 115 as that is what the vin # starts with. I think it has the old style glow plugs . I can not find the timer relay anywhere on the drivers fender. The main glow plug wire comes out of the wire bundle near the firewall. I am guessing it goes from rear to front. At the last glow plug near the radiator end the wire doubles back and goes to some sort of temperature sensor? Does that make sense?
thanks
merc hawker

No voltage at the #1 cylinder glow plug
 

Still looking for the glow plug fuse and relay on the 1976 300D,. The whole search started with a cold start problem, then I found no voltage on any of the glow plugs as described in the haynes manual.
any help would be appreciated
mercedes hawker

Relay
 

The relay for my 79 is inside the car near the steering wheelshaft,just remove the foot panel and i can see it, i cannot say for certain where yours is, but have a look there.:cool:

Thanks for the reply still looking
 

Thanks for the reply I will check in the morning. Any body else have the location for a 1976 300d glow plug fuse and relay

I will look tomorrow on my 1976 300D 115, but for mattdave was your 76 115 a 300D? Because I thought I remember reading in the owners manual that the 240D had the old style pull knob, but the 300D had the key. I believe all 300D 115's had the key, well good luck i will look tomorrow.

Your right
 

Your right mine is a W115 1976 240D
Dave S

Thanks for the reply still looking
 

I checked the firewall, and the fender no joy. I will have to wait until day light to check the footwell I am guessing you all are talking about next to the steering column, above your knees if you were sitting in the drivers seat. The wire that feeds the glow plugs disappears into the main wireing harness. I would hate to have to cut that open. It seems some one will know where it is .
thanks for your continued help still looking
mercedes hawker

Hey, preglow timer relay is a silver box underneath the dashboard right by the steering wheel. Unscrew the cardboard vanity panel and look on the left of the steering column. I don't have a picture but maybe you can see a picture on fastlane. It's silver with a flange attached with screw holes. I never did figure out how to attach it but it just hangs up there when you re attach the cardboard. My glow plugs wouldn't shut off when it went bad.

Cheap part, easy fix!

By the way, please tell me you're not using starting fluid anymore!!!!!!!!!!!
Unless you are trying to kill your car.

I am sure it is one of these? maybe
 

Thanks for your reply's,. There are quite a few relays and such up under the dash. There is one that looks as you describe almost mounted on the left side of the steering column. THere is also another a little to the left it is much bigger and is mounted on some sort of bracked I guess. I am trying a picture. It is the one on the rights side of the pic correct? The auto zone price is like $130, is that correct?
thanks for your continued help
mercedes hawker

AUTOZONE??? Why? I can't imagine they'd have anything correct for an old Mercedes besides oil and light bulbs.
$130 bucks doens't seem right but I cant remember and my records are in California.
The silver box attached to the bracket further up in the dash closer to the speedo is not it. The preglow relay is not that big.
Look more towards the front (closer to the driver) and down (lower than the speedo) It should be connected by a 5 pin connector, also the pre glow relay will likely have some high amperage rating on it being it's part of the glow plug system.
Sorry I don't know where the fuse is..

Try fastlane for the part.

Does it look like this?

http://63.89.49.212/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1CQ0J3JZ41RM0PV9T5&year=1976&make=MB&model=300-D-001&category=All&part=Preglow+Time+Relay

glow plug timer relay how many pins does it have ?
 

Ok I guess pictures are not going to work. at least today. I also know that starting fluid is not the healthiest thing for a motor. This one only needs the tinyiest whiff. You really know about it if you give it too much. Well I pulled the plug off the suspected relay. It has 6 pins plus a big alignment pin. ONly 5 of the six positions have contacts installed . So is the glow plug relay a 5 pin job. Any one know how to test it?
I gotta make the donut$$, now more this evening
thanks for all your help so far
mercedes hawker

many thanks to everyone now how do we test it?
 

Many thanks everyone. Craig thanks for the picture!!!! I believe this is the animal. I do have to get to work, so thanks and again more this evening. does anyone know the test procedure for the relay??
thanks
mercedes hawker

Just In Case
 

$130 sounds really fishy to me. If it is the case that you need to replace your relay just update the plugs all together. They work way better and if one goes out then one goes out....not all of them. Not to mention the whole kit is $40 cheaper than just the relay. You will need to get one more GP though as the kit only comes for the 4 cyl.

http://***************/search/productx.aspx?sid=ievynk45qyhmjb553oj1y0my&makeid=800016@Mercedes&modelid=1192913@240D&year=1974&cid =glow%20plug@glow%20plug&gid=7164@Glow%20Plug%20Kit

I post this as I didn't see it on Phil's site. Sorry bout the competition but just makes sense.

still would like to test the glow plug relay
 

Thanks to everyone especailly the link to the replacement unit with the cost. no one knows how to test the glow plug relay?. I just read a thread that said someone took theirs apart.
thanks again

http://www.peachparts.com/shopforum/diesel-discussion/142597-glow-plug-relay-question.html?highlight=glow+plug+relay

there's some insight in that thread.

Craig's picture is the relay.

Problem solved or at least bypass success. Many thanks to all
 

Well the problem is located and bypassed. Special thanks to Joshhall reply #13, and craig reply #17. NO glow plug light no start The problem was the relay. I guess the test for the relay is to bypass pin 5 to 6 on the relay plug ( hinted at in the 1 year off '77 300d schematic in the haynes manual, and then verified first with a ohmmeter and a long test lead), and see what happens. For me turn on the key make the bypass , instant bright glow plug light wait 7seconds and start . Fired rite up and I pulled the jumper. Every thing seems good.
Again many thanks to all. Now on to the next problem.
Any one want to buy a 1976 mercedes 300D, it needs some lovin but here is quite a bit of car left.
I had to throw that in there ..... thanks again
Mercedes Hawker

Good to hear. I hope you find a good home for it.
I'll have to remember that trick.
Pin 6 is power coming in and pin 5 goes to the first glow plug in the series?
So what you did was directly wire pin 5 to 6 on harness, thus bypassing the timer of the relay? Where does the ohm meter come into play on that process?

Those haynes manuals work okay, they didn't change much in the way of electrical setup from 76 to 77.

ohm meter used to verify what I saw in the schematic
 

since the haynes manual was off by one year. I used the ohm meter to verifiy that the schematic was correct. so I checked for continuity between one of the pins and the battery + terminal ( would be power supply to the relay. Next I checked the other pin to verify that it was a direct connection to the #5 glow plug ( the output of the relay to the plugs). The jumper was installed in the connector plug that hooks onto the relay. It is almost like hot wiring a car as seen in the movies. YOu pull the plug from the relay and then just jump those two pins in the plug and you are in business. The puzzler comes in , ? How did the dashboard glow plug light get power during the bypass. on the schematic the dash light is on another pin of the relay seperate from output terminal????
PLEASE NOTE For those trying this at home please be careful to use a adequate wire size for the jump ( quite a bit of amperage there). Also remember to pull the jumper after the car starts. With the jumper installed the glow plugs are on all the time. from dead south Texas cold it only took about 5 seconds for the plugs to be hot enough to start the car.
For $130 I will probably install a high amperage momentary on switch to handle the glow plugs . I guess I did not need that part after all
thanks again for your help and the chat
have a good night
Mercedes hawker