Picked up a 81 300CD NA today, with NO key, has been sitting for several years. Got car home, jumped 12V to starter, starter could not turn engine over. Removed fan & shroud. Put a socket, and a 1/2" breaker bar on crank bolt. Had to help starter with breaker bar for 1 turn. Starter now turns engine normally.

Ran a 12V wire directly from battery to the glow plug relay. Pic, have 12V to the 5 pin socket that goes directly to the glow plugs, in relay box. DO NOT have 12V at glow plugs??? Checked, and have continuity from 5 pin plug, to glow plugs. Where is my 12V going??? Pulled #4 glow plugged, applied 12V from battery, and grounded plug, it heated up, so do not think the problem is in the plugs. CONFUSED!!

Can not upload pictures on this forum.

did you check the fuse in the glow plug relay?

__________________
[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.

Somewhat confused by what you're doing here. Do you have a key for this car? When you're doing all this "jumping" are you in the "Pre-Glow" position?

Simply "jumping" 12V to the glow plug relay won't do anything. You have to enable it to pass current to the glow plugs. One of the pins (I believe Pin 1, but check your wiring diagram) on the 4-pin connector has to be powered for the relay to pull in, which is what the "pre-glow" position on the key switch on the dash does.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Do not forget that if you have a really good vacuum pump and system . When the key is in the off position vacuum will be applied to the shut off on the injection pump. Remove the vacuum line to it for now. There is a chance you got a car with a good vacuum system that retains vacuum well.

Also if you think the ignition key lock is original order a key from the vin number at a Mercedes dealer. You are going to need one to deal with the doors anyway.

If the ignition tumblers have been replaced over time with a non matching set you are going to have your work cut out for you. There is a possibility that even if it was changed at some time. One matching the original was installed. Fortunately just a simple non chipped inexpensive item.


Once you have a key that works any key place usually has the right blanks for a few dollar spare as well.


You can of course attempt to work around everything but a new key should not take long to aquire. Remember that it is a dealer only item from the vin number and they may want to see your ownership papers. To change the ignition lock tumbler when you have no key is not the most fun job on these cars either.

DO NOT have a key. MB does not make it easy/cheap to get key. Will not order me a key until I get title in my name. About $60 up here, and will take several weeks. Do not think PO will be any help, and is 200 miles away. Figured I was missing 12V from ignition sw, to relay box last night. Luckily the 83 CD has same style relay box, so will see what wires are "hot" going to it. This 81 is in poor shape, and just not sure if it is worth putting a lot of work/money into. It is a same the PO let it go to hell, at one time it had a really nice leather interior.

I have not read all of the posts but if you don't have the Key the steering Wheel is going to be locked or if not as soon as you turn it it will be locked.

If and when you get the key from Mercedes you are going to find out if the prior owner previousl changed the Ignition Lock Tumbler.

If you pull of the connector that goes to the glow plugs themselves off of the Glow Plug Relay someone said you can get some solid core #10 wire (and that matches the pin size inside of the connector)

Essentially you cut the wire into 5 lengths (perhaps 6 inches long) you strip enough insulation off of one end of the lenghts so that they can be twisted together.
You strip enough insulation off of the 5 seperate ends so that you can stick each on into one of the glow plug connector pin holes.

You take one Jumper cable and clip it on to the twisted bundle of wires and apply the other end to the positive batter terminal for about 30 seconds or less and that will heat up the glow plugs.

I am not 100 percent sure on the gauge of the wire as the idea was not mine and I don't remember the post. I think it was posted by Bryan Carlton many years ago.

I think I found it:
Brian Carlton Glow Plug Jumper Wires how to jumper your Glow Plugs post #2
http://www.peachparts.com/shopforum/1693618-post2.html

In post number 5 of the below thread there is a pic of a glow plug relay and it shows where the glow plug relay always has battery voltage no matter if there is no key in the ignition.

glow plug code

These are the wires that go to the Glow Plug Relay from the ignition and so on. However it is for an 84 300d so the wire colors may be different but the terminal numbers sould be the same except that you might have a wire going to an Engine Temp Sensor.

Square Glow Plug Connector, what wires go to it.

#1 Red Wire with White Stripe, Run Start Input

#2 Violet (Purple) Connects to the Starter Solenoid Wire (On Turbo Models at the Terminal Block in front of the Battery) allows Glow Plugs to be on during cranking.

#3 Blue Wire with White Stripe, Goes to the Glow Plug Light. The Voltage comes from the Relay through the Light and to a Ground.

#4 Brown Wire, Goes to ground.

__________________
84 300D, 82 Volvo 244Gl Diesel

Spent the $62.50 to title/register car. Just to take a 50/50 chance that a MB key will work! MB dealership is 60 miles away, 2 trips, courthouse 35 miles in the opposite direction. So about 300 miles on the 83 CDT. Really like the turbo for hiway cruising. Back to the 81 glow plug problem, will wait a few days, and see if the new key works. Unless I get really, really bored, and attempt to bypass the glow plug relay. Thanks to the info here, now have a good idea on how to do it. THANKS

Not that it pertains much to this particular discussion, but the purple wire also turns the glow plugs off when you stop cranking the engine. I.e. if you unplug the purple wire your plugs will glow for the full 30 seconds even after the engine starts (useful in the winter).

-Rog

Cannot arrange to fax stuff? I would have thought when living in a region like yours work arounds would be more common. A quick note from the local police that the car is yours for example. Sad if they do not exist.

We live in a low density population area of eastern Canada. Compared to heavily populated areas we scratch each others back somewhat as an expression. Our official center to get the heavy stuff done is 125 miles away.

We have some local presence in many things but that is the closest Mercedes dealer as well. For example. If I did need a key. I probably could works something out where I did not have to drive to the dealer. Not certain without trying of course but perhaps possible. Our province of Nova scotia has less than a million people as the whole population base.


If I had known of the circumstance you would experience in getting a key. Especially the overall cost in your situation. Plus the possibility the car is too far gone. I may have listed the requirements to just get it running.


This is only one reason but an important one of why we like living here. It is possible to do many things that equalize things. I call it just a common sense way of dealing with some of the realities is present.

If the 81 300D is not a turboed engine the purple wire is attached to the Starter Solenoid.

__________________
84 300D, 82 Volvo 244Gl Diesel

I see. Does it afterglow by default then? Or no way to bypass the interruption?

-Rog

Local MB dealer required, drivers license presented by ME, and a copy of title/registration in MY name. He would not take a bill of sale, and signed/notorized title from seller. MB dealer up here is not much help. When I asked if they carried any vacuum "T's" he made it clear that they DO NOT carry any parts for these older models, and they DO NOT want to work on them. It is a shame because I order a lot off parts. Thankfully we now have the internet, and do not need the dealers.

Got bored, so by-passed the glow plug relay. Used 5 alligator clips, into the 5 pin connector, then hooked the 5 ends together, then ran jumper wire to the battery to supply needed 12V. This worked. Used #14 wire, glow plugs must draw a lot of amps, wires got hot within 60 seconds on. Glowed for 30 seconds, ran starter for about 30 seconds. Engine would not start, tried "catching" a couple of times. Engine has not been started in many years. Car was last licensed in 02. Starter was not turning vary fast, even with battery charger on 200 amp boost. Think engine will start with a stronger starter. Hope new key works, will make it easier to unload, and get into shop, to install new starter.

I didn't read everything above. Was this jumping the glow plugs done without the key still? The IP would not get fuel because the key was in the off position, cutting off fuel via a vacuum valve in the ignition. Remove the vacuum line to the shut off valve on the IP and try again.

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked

When I tested a singly glow plug with a dash board type amp meter that went up to 60 amps when I applied the current the gauge pegged at 60 amps and then as the tip got hot it went down to approximately 16 amps.

Unfotunately the meter only went up to 60 amps.

__________________
84 300D, 82 Volvo 244Gl Diesel

I have never tested disconnecting the purple wire to see if causes the afterglow that some believe happens. So I can't comment on that.

What I know about it is that when you are cranking the Starter the Glow Plug Relay is on during the cranking and it is because even on the turboed 300Ds the is connected to the Starter Solenoid bay way of a White Wire that comes up from the Starter Solenoid to that wire Junction Block in frot of the Batter on the right fender well.

If you take that purple wire and apply it to a positive eletrical source you will here the Glow Plug Relay click on.

Attached Thumbnails

 

__________________
84 300D, 82 Volvo 244Gl Diesel