'70 250C oil pressure dilemma
 

Hello, new member here from ND. I was recommended to head over here from MBworld.org for some better technical help.

I have a 1970 250C W130 (2.8L) that I bought in early 2005 and after about 2000 miles I lost oil pressure. The gauge has been checked and it works, so I am not that lucky. :) I finally have the time and resources to get her fixed.

What I have gathered from my research is that the oil pump is driven off of a tang on the distributor. Is this correct? If so, then if that tang would break, I would loose oil pressure. Is this a good place to start? what other possibilities are there?

I am ready to take off the distributor to check the tang, but am unsure on how to set the engine to TDC on the 1st cyl. Any help here would be great. After I get this figured out, I will also be asking you about carb updates, as my Zeniths are worn out. I love this car and she deserves to be out on the road. Here is a pic:

http://i333.photobucket.com/albums/m...C/S1052133.jpg

Welcome to the Forum!
 

The folks at MBworld sent you to the right place. You have a nice car and I see a lot of active members on this forum with your model.

I have not worked on the M130 engine, so I can't provide all the answers.

I believe that you can turn the crank with a 27mm wrench to get TDC.

Did you do a search? Someone else must have had the same issue. I get a lot of information on this site, and most of the time I find it from searching. I also stumble onto things I wasn't looking for, but was happy to know something that I can use to improve my car.

These old cars are high maintenance... It would cost a fortune to have every little problem solved by a Mercedes Dealer or Independent shop. Letting some thing go unrepaired that I can fix reduces my car and if I let it pile up, then my car will be a pile. :)

I have searched for 250C oil pump, 250C TDC and a few others and didn't find what I needed.

You are correct on the 27mm socket, I turned the crank using one this afternoon, but i am not sure about/couldn't decipher the markings for where TDC would be for the number 1 cyl. I guess I could always just pull the plug and use a wooden dowel or something.

Thanks for the compliments, I really like my car, its just been a shame that it has had to sit for a while. That will be changed soon enough.

Finding TDC on #1 is easy. Remove the valve cover and crank the engine with the socket on the balancer until the "0|0" mark is aligned with the pointer (slightly on driver's side). Then look at the first two cam lobes, which should be NOT opening either valve. If this is not the case, turn the crank another 360 degrees.

Thank you!

I will get to it tomorrow and let you all know what I find, and then take it from there.

I love this forum... There ya go! Now, the next person with that question will find the answer in the search engine.

You will probably think of other stuff that needs repair. Your car will be in top condition very soon.

I know I will have other questions. :) Right now in my free time, i am researching either the weber or the holley carb conversions, as my zeniths are worn out. I need some new tires, I think I have that narrowed down, though. After that, all it will need is paint, and a few interior fixes and it will be good to go.

I just thought of an easier, similar way. Remove the distributor cap and turn the engine until "0|0" comes up and the rotor is pointing at #1 plug wire. There is a small notch on the inside distributor housing showing this.

Or that. :) I am heading out there soon and will give it a shot. thanks.

OK, I had a few distractions, but now I am ready to get this going. So, I can't find my shop manual, but I started taking it apart. I got the distributor off, but am not exactly sure what I need to be looking for.

I was under the impression that the oil pump is driven off of the distributor somehow, but I have no idea about the actual mechanism. If anyone has some insight, I would appreciate it.

Also, whats the best way to drain the fuel tank? I am going to drain it and blow out all the fuel lines and replace most, if not all of them. Then the next job will be the carbs.

Does this part on the right look familiar? Thats where I am at, I see the top of the drive shaft (its upside down, the part that is on the table, of the right shaft) Am I in the right place? :) What do I need to be looking for?
http://i333.photobucket.com/albums/m...0C/a98e_11.jpg

The shaft on the left is attached to a gear that is driven by the timing chain, so it sits horizontally in the engine. Its gears mesh with with the shaft on the right, which drives the distributor and the oil pump in a sort-of vertical position. The end that is pointed up in the picture points down when it's installed. The top of the oil pump's drive shaft engages the slot.

So it's not really accurate to say that the distributor drives the pump. They are both driven by a common shaft.

If the distributor is turning, my next step would be to remove the oil small oil pan and have a look at the sump and the oil pump's pickup screen.

I see what you are saying. What had been told to me before is that it is possible for the tab on the oil pump drive shaft (that fits into the slot on the above pictured drive shaft) to break off, and so the distributor will keep working but the oil pump won't pump.

Also, what drives the mechanical fuel pump?

EDIT: I just pulled that drive shaft, and the tab on the top of the oil pump drive shaft looked good, so I guess its not the issue.

Anything is possible. I personally have not heard of it happening.

You may be able to fish the shaft out of the distributor hole to check it. That should allow you to see the top of the oil pump's driveshaft. If you can't you will have to remove the oil pump to check.

The fuel pump is driven by a pushrod that is moved by small cam lobe that fits on the the top of the oil pump.

Now, I am no mechanic, but I know when something doesn't look right. :)

Dropped the pan and this is what I find.
I am guessing this:
http://i333.photobucket.com/albums/m...0409091400.jpg

Needs to go here:
http://i333.photobucket.com/albums/m...0409091401.jpg

Anyone care to explain what happened and anything I need to know? Is that an oil pressure release valve?