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Old 04-14-2009, 09:01 PM
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Join Date: May 2007
Location: Greensboro, NC
Posts: 117
Two mistakes, one observation, a question

Mistakes I Have Made In the Last Month:

# I installed the ten-degree offset key in the wrong direction, increasing my ten-degree chain stretch to twenty degrees. (Yikes!) I reinstalled the key last weekend. So that the future may learn from my stupidity, I have attached a diagram illustrating the correct use of offset keys.

# I have been jumping the glow plugs because the relay has always been spotty when the car sits more than a week. I thought I would get the job done if I connected the glow plug on cylinder four to the positive battery post with a length of twelve-gauge wire, and disconnected after thirty seconds. Not so. Reading the FSM I see the glow relay in my 240D (which is stock, not the Duratherm stuff) would keep the plugs lit until the starter goes off. Noted.

Observation On The Accuracy Of The Much-Villified Camshaft Timing Method:

# With the camshaft timing key inserted the wrong way, the camshaft timing mark method showed the valve timing was 6* late. The results from the 2 mm lift method were a little more difficult to decipher. The raw reading off the harmonic balancer was somewhere above 25* ATDC; it was impossible to tell what the actual reading was since the marks on the balancer stopped at 25* ATDC. I estimated the reading was near 35* ATDC. Because the manual states that the reading should have been 11.5* ATDC using the 2 mm lift method, the result was about 23.5* late.

With the camshaft timing key inserted the correct way, the camshaft timing marks show the valves are 4* late. The 2 mm lift method gives a raw reading of 12* ATDC, or 0.5* late.

I am not sure why these discrepancies occurred, but they are enough to convince me not to trust the camshaft timing marks in the future.

Question: What is the likelihood I have damaged the valves or pistons by trying to start the car for a month straight with the valves 20* late? (I plan a leak-down test this Friday with the Harbor Freight kit, using their $8 compressor.)
Attached Thumbnails
1978 240D won't start-woodruff-key.png  
'Betsy the Getaway Car' : 1978 MB 240D, 582k
'The Mistress of the Sea' : 2001 Giant Boulder, 10.30k
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Old 04-15-2009, 12:32 AM
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Join Date: Nov 2004
Location: Nova Scotia, Canada.
Posts: 6,510
Basically equivelent to being retarded a tooth on the cam sprocket is eighteen degrees at the damper or balancer. The intake opened a little later so that is fine as the piston was already further down the bore. The exhaust valve was a little late closing but still in closing motion as the piston came up to the tdc.

I think you will be allright. I think these engines can deal with being 18 degrees retarded and the valves survive it. Probably not a great deal more though.

I would just start it up. It will be obvious if a valve where bent. Let us know.

Last edited by barry123400; 04-16-2009 at 06:28 PM.
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Old 04-15-2009, 09:25 PM
Registered User
Join Date: May 2007
Location: Greensboro, NC
Posts: 117
If you say the valves can survive being 18* degrees late, I'll hold my breath and hope that goes for 20* too.

I wish it was as simple as "just starting it up." With a new, full-charge battery (second one since all of this started), new glow plugs (measured with voltmeter), woodruff key in right this time, it just kind of chugs, slowly, and one cylinder will hit every now and then. There's some smoke now, but not nearly the mosquito-cloud that used to occur when the engine had trouble starting before.

The starter seems slower than it used to, and it seems slower than the 240D crank videos on YouTube. When I was trying to crank it today, I heard a buzzing sound that lasted for a few seconds, seemingly from the starter, although it kept going at its previous slowish pace. Back in December it had made the same sound a few times when the starter turned.

I'll remove the starter and have the dealership bench test it on Friday. Does a slow starter seem like a valid concern here? Is it common for a slow starter to keep the engine from starting? It's hard to know what's a valid suspicion after wasting three months on the same problem.
'Betsy the Getaway Car' : 1978 MB 240D, 582k
'The Mistress of the Sea' : 2001 Giant Boulder, 10.30k
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Old 04-16-2009, 05:57 PM
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Join Date: Mar 2008
Location: South Carolina
Posts: 245
It sounds like you have found the problem.
Smoke indicates the engine is trying to start.
Slow cranking can definitely contribute to a no-start condition, especially if the engine compression is low. I would also recommend that you have the battery checked to make sure it is in good shape, even if is not very old--I think you have probably done alot of cranking with it recently.
Good luck and let us know how it goes.
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Old 04-18-2009, 12:21 AM
Registered User
Join Date: May 2007
Location: Greensboro, NC
Posts: 117
Betsy rides again


She's working again. Went out for a 30-mile drive this afternoon. Runs better than before. Sure feels nice to drive it instead of working on it.

The last piece was the starter. There was a bad ground in it, and the brushes had worn down. Brought it to a local starter/alternator shop (Carolina Quality Starter in Greensboro, NC), and they fixed it for $50. It was a Bosch reman, so I know that this was the car's second starter, at least. Engine turns over much quicker now.

In retrospect, there was no single problem that kept the car from starting over the past couple of months. Here's the best breakdown of the problems that I can provide:

30 January: Car put down for service.
6 February: Turned engine CCW between a fifth and an eighth of a turn.
27 February - 2 April: 10 degree woodruff key inserted backward, making timing 20 degrees late.
2 March: Battery replaced, shorted cell.
8 March - 11 April: Jumped glow plugs directly from the battery before cranking (spotty relay), but did not realize that the glow plugs should stay energized while cranking.
1 April-17 April: Starter begins to burn out.
11 April: Battery replaced, shorted cell.

No where was fuel starvation a problem, although I thought it was at first.

Perhaps on a cool day I will go back and do cold v. warm compression numbers for the engine. Here's what I've got already.

Woodruff key in wrong position, slow starter, cold engine at 7* C:
1. 203 psi
2. 200 psi
3. 232 psi
4. 270 psi

Woodruff key in correct position, slow starter, cold engine at 12* C:
1. 226 psi
2. 232 psi
3. 240 psi
4. 248 psi

Thanks for all the help for the last couple of months. I would be lost in fixing the car if not for this place.
'Betsy the Getaway Car' : 1978 MB 240D, 582k
'The Mistress of the Sea' : 2001 Giant Boulder, 10.30k
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