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  #1  
Old 12-23-2003, 02:09 AM
87-300E_in_NC's Avatar
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Question 2.6 Head Replacement / Timing Chain Data

After rebuilding the cylinder head completely, and starting the engine, I have experienced some difficulties in engine operation, with it cranking cold and dying when it warms. I read in a post that the computer picks up if it's out of time, but will still run the engine. I have been running my engine, but it warms up and dies, weak red/orange spark when warm. Tested TDC (crank) sensor, it passed the test. Tested coil...ok....new plugs....hitest gasoline (rust-free) and compression test passed, all cylinders.

I was wondering if my engine timing may be my case of shutting down when warmed up (along with random flooding), if the camshaft timing is not set properly, according to specifications unknown to myself. I have limited technical data for this automobile currently, and would appreciate any technical assistance.

Thanks in advance. By the way, I have a spare 3.0 head (bare casting only) with valve cover, & head bolts that I have no use for.

1987 300E 2.6 engine
Artic White/Navy interior
Aftermarket Benz Chrome rims
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  #2  
Old 12-23-2003, 10:46 AM
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WRT weak spark - can we assume that cap, rotor, coil wire, and plug wires are in good shape and that low-voltage wiring to the coil and other ignition components have clean connections and test out OK?

WRT warm stalling - does anything change if you unplug the EHA connector on the front of the main air intake? I am wondering if it is going to full enrich and killing the engine as it warms up.

Also - can you hook a dwell meter or a DMM with a duty cycle reading to Pin 3 of the diagnostic socket and tell us what readings you get as the engine warms up?

There is a ton of information on these components on this forum - you might try poking around or a Search.
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  #3  
Old 12-23-2003, 03:36 PM
LarryBible
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Follow Chucks advice. The chance of one of these chains jumping time is somewhere between nil and impossible. They have ratcheting tensioners that take up the slack as the chain wears.

You can satisfy your curiosity about the chain very quickly. Simply pull the valve cover, slowly turn the engine by hand until the little hump on the front cam stand aligns with a slot in the front of the camshaft. Then read the mark at the crankshaft damper to see that it is within a degree or two of TDC.

Merry Christmas,
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Old 12-23-2003, 03:45 PM
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Thumbs down

Thanks Chuck for the reply.

Yes, the cap and wires are new, new plugs, fuel (fuel tank just cleaned) and coil tested good also, with wire connections good too.

I was really wondering if anyone has had a simular situation with a 2.6 head replacement, with the timing marks being an issue, but you raise strong points as well Chuck. All I have to test with is a voltmeter, digital voltmeter and trial and error, along with prayer, that always helps.

I cranked the engine yesterday, and once warmed up had to rev it to clear it out, to see if it would idle or load up with fuel, and it loaded up. The engine tached 7K, and ran exceptionally well....well between 900rpm to 7K that is, but I would love to be able to drive this car.

Have not unplugged the EHA yet, as I have torn down the top of the engine to verify engine timing (cam and crank marks) once again. I did try a search on this timing topic, but only returned two results, one in which was my post. I know that there is plenty of info here about the W124's but now I'm seeking knowledge from the techs that have had this situation.

Dot on cam appears to be off a fraction from the timing mark boss on the head to the crank mark on TDC. When I attempted to align again, I rotated the engine and each time it looks off at the head timing mark. Maybe the chain is stretched? It has 212,000 miles on engine, and it is very strong. Or maybe Mercedes is designed to be set up like that and the computer compensates in engine timing.....I am not sure, but would appreciate a reply from those of you who do know.
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Old 12-23-2003, 03:55 PM
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Chucks advice?

Thanks for the reply Larry.

My chain has not jumped timing, and I don't suspect that at all, but I do suspect that I did not properly align the timing marks to get it exact, and I read where the computer will read this and not operate the engine properly.

I have no doubt that my timing chain is fine. I did verify the timing marks, and it is off by almost 10 degrees, but it reved to 7K yesterday. Does this sound right to you Larry? I am simply trying to verify that everything is in good working order, from the timing to the fuel system before I do anything else.

Also, when I put the timing back to where TDC is up and the cam marks align with the timing boss mark on the head.....I rotate the engine and once rotated it shows up as being out of time again. You are right Larry, the chain has one of the toughest and best built tensioners that I have ever encountered in my many years of being an auto mechanic, but I have not specialized in Mercedes, so that's why I am here.... .....seeking advice from the pro's. Also, I have limited technical data on hand.

Thanks for your replies.
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Old 12-23-2003, 04:45 PM
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Smile UPDATE

Now with timing marks correct (cam and #1 TDC) the rotor is not firing in the middle of the electrical contact within the dist. cap, but is off to the right a bit....is this satisfactory to the Mercedes operation of this 2.6? I realize that the rotor button has a wide electrical area to fire within the dist. cap, but it's not totally on #1 in the cap. Please advise, as I would rather play the blues without having them ( I am a musician also, play a mean 'n dirty harmonica - and now have more songs now, about my Mercedes).
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Old 12-23-2003, 05:36 PM
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There should be a tick mark on the edge of the distributor body that you can see with the cap removed. When #1 is at TDC the rotor should be centered on this mark, if not loosen the distributor and turn the body until the rotor and mark are aligned. The Germans put little timing marks all over these engines - cams, balancer, distributor. Reminds me a little of the Detroits and their timing gears, every gear is marked, align all the marks and your good to go. Aligning the distributor this way should have you just about right and the computer will do the rest.
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Old 12-23-2003, 07:16 PM
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Red face No Distributor

Hi Mike,

Thanks for the reply, but my 2.6 does not have a distributor, so that's what makes it different.

Thanks to Joe (it's German, it leaks) for the info confirmation. I aligned the marks, cranked the engine and it ran, but I had the fuel pump relay disconnected just to try to crank it, and when I replaced the fuel relay, it wouldn't crank! So, I have to pull the spark plugs to dry them up before it will crank again. Spark looks red/orange....very weak to fire so much fuel under compression.

I'll give you an update when things change (when it cranks and idles for an hour is what I'm looking for ).
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  #9  
Old 12-23-2003, 07:23 PM
LarryBible
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If it's 10 degrees off, you are lucky 10 degrees off in one direction will cause piston/valve contact. 10 degrees in the other direction will kill power.

Whenever you mess with the timing chain on these cars, you must pull the tensioner, push the ratcheting plunger all the way through and then reinsert it so that it can ratchet into place without being too tight.

Good luck and Merry Christmas,
Larry
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  #10  
Old 12-23-2003, 08:55 PM
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Ooops. Guess I should have read the post a little closer instead of speed reading.
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'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.
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  #11  
Old 12-24-2003, 03:13 AM
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Arrow Chain Tensioner

Thanks Larry for the reply. i double checked cam/crank timing again and sealed valve cover up. Now the plugs are so fouled with gas that I have to remove & clean them before they will fire the engine again (new plugs - 2nd set).....but the spark color, when warm/warming up goes faint to a red/orange. My Honda is bright blue, as a spark from solid state ignition should be...but the 2.6 seems lacking, for some reason. I thought of crank TDC sensor, but am not that much famililar with the computer system, other than the sensor could possibly making the computer out of loop, and flooding.

Anyway, Merry Christ-mas to ya as well, and to all that read these posts. Lets not forget the Happy New Year also! Hopefully it will be the year of my 2.6 engine operating exceptionally well !

Attached: My next vehicle of preference
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