300cd - No Start!!!
 

Well, the '79 300CD had been giving me problems with the key switch. It would turn but get stuck and not want to go into position 3, give a little back and forth movement and it would. The starter was also being a bit of a pain, it would engage/disengage, that problem started off slow and got worse.

Well, I got the starter off, and found bit of metal shavings in it, not surprising. I took it to the rebuild shop and they did a job on it, replaced everything they could. I got it back in the car and now there is no noise, nothing, with the key in the no.3 position:mad: . So, I waited and tried again and got the odd crank until finally I got the car started. Turned the car off and tried again, dead! No click from the starter solenoid, nothing!! I went upstairs to read the archives and my manuals etc, after a couple of hours I tired again and the starter made some clicking sounds but no poistive enagement.

So I searched the archives and went through just about everything I could.

- glow plugs are good, get lots of heat there. They are series plugs but all are working, no open circuits.

- tranny safety switch appears to be good, backup lights come on.

- battery is fine, when it did crank it did it well, I even boosted it off my other car, 300TD, just in case but no go!

- all battery/starter connections are solid, cleaned and double checked them twice.

- I jumpered the starter to the battery and the starter takes off like it should, very quick and positive engagement. Engine turns over fine.

About the only thing I did find was oil dripping out of the start switch behind the dash. So I guess a new shut off vacum switch is needed on the IP (terminology may not be exact?). I can't imagine that the oil would have done anything to the switch but??

I took the tumbler out of the start switch and it seems to be fine, I can turn the key with no problem. With the tumler in the start switch all turns fine as well, not like before where it would it would not go into no.3 position.

So, I am guessing that the start switch is faulty. How do I get that sucker out of there?? I pulled the connector behind the switch and relaeased the clamp near the column but no go, am I supposed to have the switch/key in a certain position to release it? The switch itself appears to be serviceable with three screws holding the rear cover plate on. I would like to have a look in there to see whats what, I have had a start switch fail once before(Landcruiser FJ40).

I looked in my Haynes manual and on the MB-CD but no mention of how to pull that switch mechanism out. I searched the archives here too.

Later today, if I don't figure out how to pull the starter switch out, I will measure the voltage at the starter to be absolutely sure that there is no voltage with the key in the start position. I will also jumper the tranny safety switch, just in case.

If anyone could tell me how to get the start switch out it would be helpful.

no experience with this, but
 

It seemed like you might not be using the right key words.

Did you try



IGNITION AND LOCK ?


Just a thought

Best of luck...

I certainly did use ignition for a search! Didn't want to use it again in my own spiel, PEH might slap me one for using improper terminology:rolleyes: . hehe!

I also found a little time at lunch to more carefully read my Haynes manual and as I half suspected the key does have to be a certain position to be able to pul the whole thing out. I will keep everyone aprise of my progress or lack thereof.

I believe the ignition switch is held on by two screws (may be three?). Pull the connector off (it is keyed), screws accessable with connector off.

Oil leaking out means bad shutoff solenoid or leaking vac pump, you need to fix whichever it is.

Peter

Ignition switch problem sounds like bad tumbler to me. I had to replace mine.

Problem solved! :D:D:D:D

The ignition/start switch is ok. I finally got it off of the column. There is a little retaining pin that sticks out of the shaft in which the whole mechinism sits. A bit a foam isolation was partially covering the pin but I found it and got the bugger out. The electrical contacts inside the switch were a bit pitted, so I ceaned them up. I tested the continuity between post/terminal 30 and 50 and all was well with the switch. I then put everything back together and gave her a try, NADA!!! Grrrrr!!!! Dead again!!??!!!

While I had been getting the backup lights to work when putting the shifter into reverse I thought there must be more than one contact in that switch on the tranny. Perhaps it was not making contact for the start circuit, hmmmm.

Anyhow I jacked up the car and crawled under (jacks stands in place holding the load) and had a look see. Well, the electrical connector to the switch was half busted. The connector has four wires, two for the backup lights, two for the start circuit. The wires come out of the connnector at one side, not straight out the the back. The side where all four wires enter the plug was messed up allowing the connector, which has two halves, to split apart, albeit very slightly. The two wires closest to the split were the ones for the start circuit. With the connector splitting there was just enough pressure to pull one of the connections lose, hence the problem. WHEW!! So when I cleaned it all up and re-inserted the connector guess what? VRROOOOMMMMM!!! That puppy fired up just fine! Oh the sweat smell of diesel, heck it smelled better than the neighbours BBQ!!

So now I have to get a new connector to attach it all to the tranny properly. Resoldering the wires is not going to be allot of fun but hopefully I can work around it. There is not much room and the wires are fairly short so....

Anyhow, more parts to order. The shut off on the IP is looking kinda oily, I'm surprised it still works.

Well to get around soldering I always use wire crimps. Though, if you're good, you shouldn't have a problem w/ short wires and soldering them. You can even splice some more wire in there to make it longer.

Greg:

This is a Benz! Don't cut the wires, just unclip the back of the plug and pull them out. The wires are soldered to plated cylinders, into which the pins on the switch go.

You will only have to take the old plug apart, insert the cylinders into the correct holes, and put the new plug together. Very simple, much better than wire crimps, etc.

Peter

Yup, I was hoping to be able to pull the wires and soldered contacts thru the opening to the connector and put it back into the new connector. I would not have cut any wires, would have just meleted the solder.

Hi Greg,if the CD is shutting off ok with the switch and you have oil dripping from the start switch,it's probably the vacuum pump.Check the air cleaner housing,when the diaphragm goes bad it pulls oil through the line from the pump.Good luck :)

Hey!

The air cleaner housing appeared to be fine. How much oil would there be though? Would there be enough for it to be wet? stain the filter? Would there also be oil in other vacuum lines?

I will check the shut-off valve and see if it holds out. There was a fair bit of staining on the insulation below the switch, I wouldn't doubt that it has been leaking for a while. Then again the amount of oil in the switch was pretty minimal. Hmm, we will see what the tests results are.....

Tx!