Top Dead Center Issue
 

I have 1990 Mercedes 560 SEL. I recently replaced the hydraulic suspension pump. I took off the distributor so that it would be easier to get access to the bolts. I was careful not to move the distributor rotor, but I must have moved it because now I can't get the car to start. So I then aligned the pointer on the timing chain cover to TDC mark on the vibration damper (the big zero right ???) I aligned the rotor to the notch on the distributor housing. still won't start http://www.benzforum.com/forum/image...s/confused.gif I aligned the pointer to the TDC mark by using the ignition switch to turn the motor. The pointer wasn't exactly on the TDC mark, but it was pretty darn close. How can I turn the engine manually so that I can align it exactly? I read that I should turn the crankshaft bolt. Where is that? Can the rotor be the issue? The car started like new until now.

Thanks and Merry X-mas :)

I don't have that car but this seems like a basic issue. First of all, don't fixate on the distributor since you might have disconnected something else so don't get tunnel vision. However, you could be right. Now remember that TDC occurs twice, once on the compression stroke and once on the exhaust stroke. You want the compression stroke. If you are on the exhaust stroke then you will be 180 degrees off and it won't start for sure. I did that once...

As for the crank bolt, it is in the middle of the crank pulley on the front of the engine. Usually you need at least a 1/2" drive ratchet for leverage and a short extension to get to it but again I don't have that car so I can't say specifically.

I don't know about the marks on that car but generally you align the pulley to the 0 mark and then move the distributor cap so the rotor points at the electrode for wire #1.

Hope any of that helps.

Welp, I guess I can spend this christmas under the hood for a few hours. Thanks for the tip mpolli. I guess I was 180 degrees off like you said because I set the TDC at zero, and I aligned the rotor. I will try to find the crank bolt and set the TDC manually. How do I know if I am on the compression stroke without taking off the valve covers ?:( Also, what are the two U-shaped cutouts on the vibration damper for?

Well I don't have a clue about the cutouts. You might try searching. As far as the compression stroke, well you could just try moving the cap 180 deg and see if it starts. Or you could remove the #1 plug and see which time it makes compression (pushes air out). A compression gauge would be handy for this but you could probably just feel it with your finger (turning the engine slow with the ratchet!).

Turnng the cap 180 is probably not possible. You will need to remove the dist. and rotate the rotor 180 then reinstall. gEt it close then put on the timing light and twist the dist body until you get the timing just right.

There is no timing adjustment on a 560. The timing is determined by the crank sensor on the flywheel. Rotating the distributor doesn't change the timing. It can misalign the outputs though. You will note how wide the rotor tip is, that is so it isn't critical where the rotor is when the spark is created as long as the rotor tip is generally pointed at the proper plug wire.

The cut-out are for balancing.

The way to tell if you are at TDC #1 would be to take the valve cover off the right side and look at the cam lobes on #1 cyl, but that is too much work. You either are right or one turn of the motor wrong. Either find that bolt in the center of the harmonic balancer and turn it or take the distribiutor out and point the rotor 180 deg from the #1 position.

well, looks like the crankbolt is the easiest way to go. the TDC line has to align PERFECTLY with the tip of thetTiming chain cover. The hydraulic pump is finally fixed :P what a relief. thanks for the help and info

The hydraulic suspension pump is the reason I had to take off the distributor in the first place. Here is a step-by-step with pictures. I hope this helps anyone that ever has a 560 SEL (or similar model) with hydraulic suspension.

First, remove the reservoir intake tube.

http://i417.photobucket.com/albums/p...t/DSC_0008.jpg

Next, remove the banjo bolt.

http://i417.photobucket.com/albums/p...t/DSC_0007.jpg

This picture shows the intake tube. Follow the tube until you find a bolt that secures it to the engine block. If you don’t, it will be really hard to remove this line from the hydraulic pump. I didn’t do this and it was a PITA !!!

http://i417.photobucket.com/albums/p...t/DSC_0001.jpg

This picture shows the bolt that you will need to remove so that you can take the distributor off. You will need to do this so that you can have easier access to the hex bolts on the pump. This is where I got in trouble:rolleyes: When I re-installed the distributor I had moved the rotor, so when I tried to start the benz-O, the timing was off and it wouldn’t start :confused:. You will need a 27mm deep socket, a 2 inch extension, and a good sized ½ inch drive ratchet wrench. I removed the fan to get easy access to the crankshaft bolt. Make sure to mark one bolt so that they all go back into the same slots, just to be safe.

http://i417.photobucket.com/albums/p...t/DSC_0002.jpg

This is the pump after I took it off. Notice that there are two hex bolts still on. These hold the two pieces of the pump together.

http://i417.photobucket.com/albums/p...t/DSC_0004.jpg

This picture show the hydraulic pump with the new seals. Now I will take the time to gripe about why this had to be done in the first place :cool:. I went to the local indie shop, which up until a few months ago, was the only game in Denton, Texas. I asked for hydraulic fluid, but I got power steering fluid. When I went back, the idiot (who is also the owner !!) reassures me that the fluid is the same. The even bigger idiot (me :o) loads up the reservoir and a few days later, instead of just having a small leak from the pump-to-block seal, the pump leaks internally :eek:. Thanks a lot Dave’s Import !!!! :mad:

http://i417.photobucket.com/albums/p...t/DSC_0003.jpg

Installing is the reverse. Hope this helps someone :D