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  #1  
Old 01-05-2003, 10:42 PM
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Question cyl. head changed - engine won't start

I've changed the cylinder head on my 89' merc 300sel 3.0l 6 cyl line M103 engine and the engine won't start.

First, I checked the timing marks in case I have wrong timing. The mark on harmonic balancer (OIT) is off approximately 5 degrees to the small pin on timing chain cover (next to TDC sensor). ---I think it's OK.

Then, I checked if I have sparks on each cylinder using the ignition gun. Yes I have sparks on each cylinder.--- my spark plugs are working.

After that, I checked the compression in each cylinder. 1-95 2-87 3-95 4-110 5-110 6-150psi --- I got the compression.

When I checked the compression I had to remove all the spark plugs. I could see the air-gas mixture coming out of each cyl. from the spark plug holes. --- I guess I donít have problem with the injection system because I have gas coming into the cylinder.

I have gas injection, compression and the spark! The engine should start but it doesn't

Any ideas what could be wrong????


Last edited by brookolli; 01-06-2003 at 12:58 AM.
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  #2  
Old 01-06-2003, 12:59 AM
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Take another look at your compression figures, you have 150psi on #6 and only 87psi on#2. That's quite a bit more than the accepted 10% varriance.

When you say you have the timing off by 5* at the crank pin, what does the timing mark at the cam show? Likely the cam/crank position are off just a tick which would give you low compression figures. The big question is, did you bend any valves having the cam/crank relationship off?
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  #3  
Old 01-06-2003, 01:09 AM
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The cam mark is (little hole on the lip) is at the crest of the first rocker arm assembly when the reading on the harmonic balancer shows ~5 to the right of (OIT) in relation with the pin on timing cover.

How do I know if I bent the valves?

Last edited by brookolli; 01-06-2003 at 01:27 AM.
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  #4  
Old 01-06-2003, 07:29 AM
LarryBible
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I also expect that timing is not correct. These timing chains have a small pitch, so it's easier to get it off by one notch than on the diesels with the larger pitched chains.

If the cam timing is retarded, then you did not bend valves, if it is advanced, you probably did, and that is why you are seeing the compression variation.

I think you should pull the upper timing cover and ensure that your timing is correct. Also, did you reset your ratcheting tensioner?

Good luck,
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  #5  
Old 01-06-2003, 10:59 AM
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Anytime you do anything with the timing chain, such as replacing or removing for head work, you should always manually roll the engine over at least two complete revolutions. You roll it over at the crank bolt and two revs takes you through a complete cycle. If you did this before hitting the starter, then likely your timing is retarded. If timing was advanced, you would not be able to make two complete revolutions by hand due to piston/valve contact.
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  #6  
Old 01-06-2003, 08:17 PM
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One tooth on the timing chain is about 14*. I have had this happen where the lifters pumped up tight and the engine would not start. So. Replace plugs. Hold throttle wide open and try. If engine starts, let of gas. Also, check for vacuum leaks.
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  #7  
Old 01-07-2003, 12:31 AM
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Donnie,

When you say the "lifters pumped up tight", am I correct in assuming they pumped up from building oil pressure while trying to start the engine?

Definitely something to keep in mind. Not something one would expect to encounter.
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  #8  
Old 01-08-2003, 12:20 AM
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I kept cranking the engine for about an hour and it started. New lifters were pumped up that's why I got various compression in the cylinders.

Thanks for replies
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  #9  
Old 08-08-2011, 02:48 AM
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Angry

Quote:
Originally Posted by MikeTangas View Post
Anytime you do anything with the timing chain, such as replacing or removing for head work, you should always manually roll the engine over at least two complete revolutions. You roll it over at the crank bolt and two revs takes you through a complete cycle. If you did this before hitting the starter, then likely your timing is retarded. If timing was advanced, you would not be able to make two complete revolutions by hand due to piston/valve contact.
I am having similar problem with my car. It is Mercedes 300E, 1993 V6, 3.2L. I made a mistake of not setting my crank on TDC before I changed a leaking head gasket. I have tried 100* to set my timing chain in vain. I have followed all the procedures outlined in the manual and what the MB experts have adviced hear to no avail.
-Everytime I set TDC and dowel marks as adviced and set the intake camshaft in the retarded position, the engine will not go through two complete revolutions without getting stuck. I am rotating the engine clockwise while standing infront of the car facing the engine/ motor. It this the correct engine rotation or am I doing it wrong?
- I tried to set everything again as above and rotated the engine counter clockwise and the crankshaft completed 2 revs to get back to the previous mark (TDC). However, I could not rotate the crank/engine when I tightened the chain tensioner all the way in and my timing chain is getting very tight to the point that I am afraid it might break. Please help me with:
*direction of the engine rotation. Why do I have valves touching the top of cylinder in either direction?
=timing chain tightness issue...what would be the remedy? I always disassemble the chain tensioner before I put it back to manually rotate the crankshaft.
I am waiting dumbfounded. I don't want to mess this baby because the body and interior are such in such an excellent shape.
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  #10  
Old 08-08-2011, 05:24 PM
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Red face

Is anyone out there to help me? Pleaaaase!
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  #11  
Old 08-08-2011, 10:24 PM
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oldkili98, at this point your best bet is to remove the rockers so that you can turn the engine without binding. Then you can get the engine to TDC @ the Crank, then line up the cams. Once you do, when you start to replace the chain, if it is NOT TIGHT you may need to ADVANCE the cam(s) slightly to get the chain on properly so it's timed right. Then you will most likely have MUCH more slack in your tensioner which is currently losing slack due to the valve/piston interference. I got lucky when I did my car's timing belt and although the cam jumped on both banks and I couldn't turn the engine, I guessed where the cams should go, and after turning the engine by hand 10 times because I couldn't believe my eyes, it turned out my timing was DEAD ON by lucky guess.
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  #12  
Old 08-09-2011, 04:12 AM
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Angry

Tomboy, thanks for reply. I still need to confirm the direction of engine rotation on this m104 because I don't want to put it back wrong and end up with bent valves. I do agree you were very lucky to have the timing chain back right without the struggles/ frustrations I have to endure. I will follow your advise and see if I can get a little more slack on my timing chain.
One more thing....could it be because I put the chain tensioner wrong?

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