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Greetings,
Recently, I replaced the head-gasket on 97 Mercedes E320. The head was machined and I put on new bolts and torqued them to the specs. I put everything back together but I ran into this problem that I am trying to resolve. I am not sure what is this component called but if you look at the images, you will see that it not seated on the valve cover as it should (image #1). Inside this component, there is a gap that’s approximately 3/4″ round and it’s placed over what looks like a knob that sticks out of the valve cover and spins freely inside this thing. The first thought that came to my mind was that the camshaft was not seated/torqued properly as they took them out as the shop to resurface the head. I removed all brackets and checked to make sure it was installed properly; everything looks good there (I think). Back to image #1, the surface of the head is aligned with and valve cover surface, when I move my finger over, I can barely feel there is a groove in between, so I keep going back to the camshaft that is probably not aligned with something else. I decided to not install it and start the engine to make sure everything else works and something else came up. The engine cranks for 1 sec or less and stops. Battery, starter, etc., are good, there is spark, there is fuel, no issues there. I went ahead and tried to crank it manually and it turns only for about 45 degrees and stops. I am almost positive that there is a connection between this cranking issue and how that component is not aligned with the camshaft as I described in the beginning. Is it possible that the camshaft is bent though I can’t visually tell? What are other things to check for? Right now I would like to focus on getting the camshaft aligned with that thing and if I get to do so, I think the engine should turn over. Also, can I manually try turn the engine with both camshafts removed to make sure nothing inside the block is causing any issues?I have an audio of what the short cranking sounds if that may help.
Thank you for taking the time to read this, I would appreciate any kind of response!
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Your component is question is the camshaft position sensor. A faulty, or in this case not correctly installed, CMP sensor will cause a condition like you describe. What happens is the crank position sensor sees the crank turn after the starter engages and says, “ok looking good so far”. Then once the crank turns 2 full RPM and the CMP sensor never shows a signal, the computer says “I don’t know when Cyl 1 is at TDC of the compression stroke, so I’m done trying to start”. That’s when it will stop cranking every time after 2 RPMs with no CMP signal. I might be wrong if your car some special Mercedes thing, but sequential fuel injection systems normally use this logic.
As for your actual problem, I don’t know what’s going on there that’s out of alignment. If that cam was actually crooked enough to look like that in image 3, it wouldn’t even mount in the bearings much less turn at all if forced together. It seems like timing chain cover is installed fully to the end of the head. All that leaves is that the cam sprocket might be crooked on the end of the camshaft so it walks around in that opening. Can you turn the engine by hand and watch for that? To answer another question, you can turn the crank freely with both cams removed because all the valves will be closed won’t interfere with the pistons.
Thank you for the answers!!
Visually, the camshafts do not look bent at all and they are seated well and the brackets go over them with no resistance. The sprockets look good as well, but I will try what you suggested and see what happens.
So, if the engine turns with both camshafts off, what would that tell us? Although I carefully marked the crankshaft, sprockets, etc. before I removed the head, what would be the best way to tell that the timing is correct? Also, if the timing is off would that cause the engine to lock up?
If timing is off to the point that valves hit pistons, it will make the engine lock up when turning by hand but the starter torque is usually enough that it can just force it and bend valves out of the way. If the engine turns with both cams out, all that says is that the crank/rods/pistons move freely which I think is already known good.
As far as making your own timing marks on a used chain for reinstallation, I’m not a fan of that method because of how most chains time up. If the chain has the factory timing marks or colored links or whatever worn off, I’ve always gotten a new chain with the marks properly on it. To me the way to know timing is correct is to use factory markings. I don’t know your specific engine at all, so I can’t say anything too worthwhile here. If I get a chance at work, I can look up the factory service information and see what I think of it.
If that cam sprocket doesn’t walk around in that hole when you turn it, I don’t know what the heck it going on there based on what I can see in the pics.
If you get a chance, that would be appreciated!
It just sounds like something is blocking it, like an obstacle or something. I think I will redo the timing just to be sure, check the sprockets while turning the engine by hand and go from there.
Here is what the cranking sounds like by the way:
[quote=”RochNoure” post=120728]
Here is what the cranking sounds like by the way:[/quote]It’s very important to get things lined up mechanically. If not, you can damage the engine. I would first recommend you make sure there everything is in time correctly. If not, correct it, and try and spin the engine by hand again. If it rotates freely, then properly position the cam sensor as suggested and then try and start the engine.
Good luck and keep us posted.
I went ahead and removed both camshafts and spark plugs, tried to rotate the engine by hand and it only turns for about 30-40 degrees and stops. Should I remove the cylinder-head then try to rotate it again? I just want to make sure the block is healthy internally. If it rotates, what could possibly be wrong with the head?
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