300D Part I.D. - Problems Starting
 

There are two parts to this post. The first is: What is the part that's in the photograph below? It's located behind the driver's side headlight.

The second this is that my car won't start. Here is what I know so far:

- The battery has plenty of juice (I tested it with a voltmeter and all the accessories turn on with no problem).

- The starter does not engage (doesn't even make a noise) when the key is turned.

- I ran a wire directly from the starter power terminal to the battery terminal. The starter still is completely dead when doing this, however there is a clicking sound coming from the part I photographed below (maybe its a relay)?

- The ground wire from the bell housing to the chassis is clean and has good connection. What other connections could be affecting it?

- No fuses are blown.

I'm thinking the issue is either some sort of relay or that the starter is bad (I just replaced 7 months ago with a remanufactured one).

http://i1219.photobucket.com/albums/...6/300DPart.jpg

Thanks in advance for your help.

Brendan

Glow plug relay, yes? The car won't start without it, or one like it. Why the starter won't engage, maybe a bad new or reman starter, or a bad ground, start with the latter. Could have simply not been grounded securely when replaced and has come loose.

There's a plastic junction box on top of the right fender in front of the battery. Try jumping terminals 1 and 3. If that does not cause your starter to activate, you have a ground problem, a connection problem at the starter or a problem with the starter itself.
It is in Park, correct? A bad NSS can cause those symptoms.

The reason the Glow Plug Relay in the picture is clicking is that when your Key is in the Starting Position and the Starter Solenoid gets Electricity there is a wire that comes up from the Starter Solenoid Terminal and connects to a Violet (Purple?) wire that goes to the Glow Plug Relay.

While the Starter is Cranking the Violet Wire gives your Glow Plug Relay Electricity and your Glow plugs are on while your Engine is cranking.

In other words the relay is fine and is just clicking because the starter isn't cranking?

Update, I had the starter bench tested and its in good working condition. So that only leaves a bad ground or bad connection to the starter right? What grounds are there besides from the bell housing to the chassis?

There are other possibilities if the starter is good but not working in the car. Try jumping the terminals that kerry suggested, if it works the problem may be elsewhere in the starting circuit including the ignition switch or the neutral safety switch on the transmission. Also, try starting it with the car in neutral instead of part and try wiggling the shift lever around.

extremely common issue with these older mb's
it's the shifter bushings on the transmission shifter linkage.
try this. put your emergency break on solid!, then put key in, let the relay click, and wait 25 seconds, then turn the key to the start position and hold it there. now with your left hand, reach under your right hand, and push on the shifter in park, wiggle it to the right while pushing forward. usually this will solve the issues. if it starts fine this way, you need to order all the bushings for the shifter and linkage. it's not hard to change all the bushings, but you will need to get the console out, and get to the shifter parts, and under the car on the linkage to the transmission.

Alright guys, I'm starting to loose hope here... I tried:

- starting it in neutral, and tried wiggling it around too

- starting it how vstech suggested with the ebrake on and wiggling it in park

- jumping terminals 1 and 3 (heard a click from the relay again)

- cleaning off all ground and power wire terminals with simple green and a wire brush.


The only things I can think of is that the battery is low now from trying to start it so much, or that there's a fuse blown that I don't know about. All the fuses are located on the drivers side against the fire wall correct?

A weak battery could indeed be hindering your progress - can you jump start or borrow another battery? Your battery should physically fill the battery tray - sometimes people fit smaller ones 'cos they are cheaper but they aren't always up to the job when they get a bit older.

As I'm paranoid I'd also check to see if I can turn the engine by hand - crankshaft nut 27mm

Good luck.

I don't think any fuses are involved in starting (aside from the relay's fuse which has nothing to do with the starter). It's key->neutral safety switch->starter. Plus if you want to skip all that you can take a small wire and hook the solenoid screw on the starter directly to the battery.

If you want to trace a voltage issue you're going to need a helper to turn the key when trying to start. First, I'd disconnect the GP relay while troubleshooting. That eats up alot of juice and will do more to wear down your battery than anything at this point. You'll need a voltmeter too.

If you are hearing no clicking from the starter relay then you need to find out why. The two connections on the fender are the battery and the starter relay. When the ignition switch is engaged to START, you should see 12V appear at the starter relay terminal. If not, then check your neutral safety switch. If your glow plug relay is energizing, then your NSS should be working. If the starter relay is energizing but not engaging the starter, check the ground from the engine to the chassis. You can test this by engaging the starter and checking the voltage from engine block to the negative battery post. If you see any voltage at all, then you need to tighten/fix your ground connections to the battery and/or engine.

Another way to test the engine ground is tho connect a jumper cable from the engine to the negative battery terminal and see if it works then.

Thanks guys. I will try all those suggestions.

"Army" - The battery is brand new (has about 5k miles on it) and it does take up the entire tray. I'll try cranking the engine manually like you suggested... I hope that's not the problem!

"aaa" - I've already connected a wire directly from the starter solenoid screw directly to the battery and still nothing other than the relay clicking.

I'm assuming since directly connecting the wire didn't work that it must be a ground issue. Running the wire from the solenoid screw to the battery should bypass all the other potential issues regarding the NSS, shifter bushings, etc. Right?

If you pulled out the starter and it worked fine on the bench, then yes, it appears something is wrong with the electrical connections to the starter when it is installed. So I would try if possible to bypass the standard electrical connections in the car and jump it while in the car. Ground the engine or starter to the negative post on the battery as Craig suggested and try it. If that doesn't work, also jump the positive post on the battery directly to the starter if possible and see if that works.

On a related note, when I have jumped terminals 1 and 3 in the junction box, I don't remember the glow plug relay clicking. Does anyone else?