Re: [MBZ] OM617 - Identifying real crank position
I'm with Peter on this one. First chain replacement I ever did was on almost the same engine (OM617.912) and I also managed to skip a tooth, but checked my work, found the problem, and corrected it. If you don't want to pull the pre-chamber (I didn't either), I think you'll have to determine skip or not skip by experimentation. Rotate the engine through several complete revolutions by hand to make sure there's no piston/valve interference, button up and drive the car and judge the power output. If not satisfactory, move chain one tooth on camshaft gear, verify no interference between pistons/valves, then check the power output for improvement. Decide which position is better. I'll bet that your harmonic balancer is fine and is reading true. -Max -Original Message- From: mercedes-boun...@okiebenz.com [mailto:mercedes-boun...@okiebenz.com] On Behalf Of Peter Frederick Sent: Friday, November 05, 2010 8:24 PM To: Mercedes Discussion List Subject: Re: [MBZ] OM617 - Identifying real crank position Yes, you can remove the bottom oil pan. Messy, but should work. You can also pull the #1 prechamber and use something like a coat hanger wire to determine when the piston is at TDC. Even just pulling the injector or glow plug should let you know if you are close. Stops blowing and starts sucking in air at TDC on the compression stroke. Or you can assume you have jumped a tooth, which is rather common -- I've done it twice. I believe they are 13 degrees each, so it ads up pretty well, and you would be within 2 degrees if you move the cam sprocket. It will run just fine, although low on power with the cam 15 degrees late. 15 advance and the pistons hit the valves. Peter ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] OM617 - Identifying real crank position
There is always option C. Removing the cam lobes/retaining nut/spring on number one and rotating engine until the valves dont drop in the engine... I would take this over pulling prechambers any day... -Rolf On 11/09/2010 07:47 AM, Dillon, Meade M CIV SPAWARSYSCEN-ATLANTIC, 53310 wrote: I'm with Peter on this one. First chain replacement I ever did was on almost the same engine (OM617.912) and I also managed to skip a tooth, but checked my work, found the problem, and corrected it. If you don't want to pull the pre-chamber (I didn't either), I think you'll have to determine skip or not skip by experimentation. Rotate the engine through several complete revolutions by hand to make sure there's no piston/valve interference, button up and drive the car and judge the power output. If not satisfactory, move chain one tooth on camshaft gear, verify no interference between pistons/valves, then check the power output for improvement. Decide which position is better. I'll bet that your harmonic balancer is fine and is reading true. -Max -Original Message- From: mercedes-boun...@okiebenz.com [mailto:mercedes-boun...@okiebenz.com] On Behalf Of Peter Frederick Sent: Friday, November 05, 2010 8:24 PM To: Mercedes Discussion List Subject: Re: [MBZ] OM617 - Identifying real crank position Yes, you can remove the bottom oil pan. Messy, but should work. You can also pull the #1 prechamber and use something like a coat hanger wire to determine when the piston is at TDC. Even just pulling the injector or glow plug should let you know if you are close. Stops blowing and starts sucking in air at TDC on the compression stroke. Or you can assume you have jumped a tooth, which is rather common -- I've done it twice. I believe they are 13 degrees each, so it ads up pretty well, and you would be within 2 degrees if you move the cam sprocket. It will run just fine, although low on power with the cam 15 degrees late. 15 advance and the pistons hit the valves. Peter ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] OM617 - Identifying real crank position
Rolf wrote: There is always option C. Removing the cam lobes/retaining nut/spring on number one and rotating engine until the valves dont drop in the engine... I would take this over pulling prechambers any day... I'd pull #1 glow plug, fit a hose to the glow plug hole, and fill the cylinder with oil near TDC. When you find the point at which the most oil is pushed out the hose, you should be within one degree of TDC. Just leave the GP out until after you start the engine for the first time, to blow out the oil. Mitch. ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
[MBZ] OM617 - Identifying real crank position
Ok, so I've replaced the chain in my 617.910. It is now perhaps half a degree better than it was before the chain replacement, but the crank scale is still reading 15+ degrees ATDC when the cam notch is lined up with the mark! (pics attached) Given the measurement margin of error, the 15 degree offset seems suspiciously close to the 18 degree offset produced when the chain is off by one tooth at the cam. I'm wondering if it skipped a tooth at some point in the past, perhaps when the chain was replaced previously (it was an IWIS chain and had almost no wear). I know this skip didn't happen during my recent chain replacement, because at no point was either end of the chain not under tension or out of contact with the cam gear. I didn't even remove the tensioner. In any case, before I go further I need to determine whether the crank scale's indicated TDC really is TDC... Apart from the scale, is there any other externally visible reference mark on the crankshaft? I want to rule out that the harmonic balancer/scale has come loose or wandered, something that seems to happen occasionally, eg if someone impatiently reinstalled it during front seal replacement. If possible, I'd rather not have to remove a prechamber to check piston position, so I'm hoping maybe there's some kind of reference mark on the crankshaft that can be checked against the scale. And given how hard it sounds like it is to properly install the balancer once removed, I'd rather not touch that either if I can avoid it. Would removing the lower oil pan be an option as a means of seeing the movement of #1 conn rod towards TDC? I haven't checked if the pan can be removed in-situ, but intuitively it seems like perhaps it could... D. -- next part -- A non-text attachment was scrubbed... Name: %IMG_1711.JPG Type: application/applefile Size: 53662 bytes Desc: not available URL: http://okiebenz.com/pipermail/mercedes_okiebenz.com/attachments/20101105/94e64838/attachment.bin -- next part -- A non-text attachment was scrubbed... Name: IMG_1711.JPG Type: application/octet-stream Size: 910453 bytes Desc: not available URL: http://okiebenz.com/pipermail/mercedes_okiebenz.com/attachments/20101105/94e64838/attachment.obj -- next part -- A non-text attachment was scrubbed... Name: IMG_1727.jpg Type: image/jpeg Size: 1361447 bytes Desc: not available URL: http://okiebenz.com/pipermail/mercedes_okiebenz.com/attachments/20101105/94e64838/attachment.jpg ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] OM617 - Identifying real crank position
Yes, you can remove the bottom oil pan. Messy, but should work. You can also pull the #1 prechamber and use something like a coat hanger wire to determine when the piston is at TDC. Even just pulling the injector or glow plug should let you know if you are close. Stops blowing and starts sucking in air at TDC on the compression stroke. Or you can assume you have jumped a tooth, which is rather common -- I've done it twice. I believe they are 13 degrees each, so it ads up pretty well, and you would be within 2 degrees if you move the cam sprocket. It will run just fine, although low on power with the cam 15 degrees late. 15 advance and the pistons hit the valves. Peter ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] OM617 - Identifying real crank position
On Fri, 5 Nov 2010 12:32:40 -0700 David Bruckmann bruckma...@transcontinental.ca wrote: Ok, so I've replaced the chain in my 617.910. It is now perhaps half a degree better than it was before the chain replacement, but the crank scale is still reading 15+ degrees ATDC when the cam notch is lined up with the mark! (pics attached) Yup, that is what it looks like. Given the measurement margin of error, the 15 degree offset seems suspiciously close to the 18 degree offset produced when the chain is off by one tooth at the cam. Is does seem suspicious. In any case, before I go further I need to determine whether the crank scale's indicated TDC really is TDC... That would be a good idea. Apart from the scale, is there any other externally visible reference mark on the crankshaft? Sorry, I don't know. I'm in Knoxville, TN, and my manuals are in Los Alamos, NM. Would removing the lower oil pan be an option as a means of seeing the movement of #1 conn rod towards TDC? Yes, but I'm not sure how accurately you could see the piston's position. The amount of travel of the piston gets quite small the closer you rotate the crank to TDC. I haven't checked if the pan can be removed in-situ, but intuitively it seems like perhaps it could... You can remove the lower oil pan, but the oil pump is in the way to readily see up into the upper reaches of the engine. With a mirror you might be able to see what you need to. Craig ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] OM617 - Identifying real crank position
Do the 910's have the rear sensor on the flywheel like the newer ones do? -- John W Reames jwrea...@comcast.net Home: +14106646986 Mobile: +14437915905 On Nov 5, 2010, at 20:33, Craig diese...@pisquared.net wrote: On Fri, 5 Nov 2010 12:32:40 -0700 David Bruckmann bruckma...@transcontinental.ca wrote: Ok, so I've replaced the chain in my 617.910. It is now perhaps half a degree better than it was before the chain replacement, but the crank scale is still reading 15+ degrees ATDC when the cam notch is lined up with the mark! (pics attached) Yup, that is what it looks like. Given the measurement margin of error, the 15 degree offset seems suspiciously close to the 18 degree offset produced when the chain is off by one tooth at the cam. Is does seem suspicious. In any case, before I go further I need to determine whether the crank scale's indicated TDC really is TDC... That would be a good idea. Apart from the scale, is there any other externally visible reference mark on the crankshaft? Sorry, I don't know. I'm in Knoxville, TN, and my manuals are in Los Alamos, NM. Would removing the lower oil pan be an option as a means of seeing the movement of #1 conn rod towards TDC? Yes, but I'm not sure how accurately you could see the piston's position. The amount of travel of the piston gets quite small the closer you rotate the crank to TDC. I haven't checked if the pan can be removed in-situ, but intuitively it seems like perhaps it could... You can remove the lower oil pan, but the oil pump is in the way to readily see up into the upper reaches of the engine. With a mirror you might be able to see what you need to. Craig ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] OM617 - Identifying real crank position
To me it is easier, (and the book procedure) to pull #1 nozzle and the prechamber. Then you put a 1/8 rod in and monitor as it comes up. Mark (on the damper) where it stops rising. Mark again where it starts to fall. In between is TDC. Do this for several turns. That confirms the accuracy. This procedure is in the OM621 book. It may be in the OM616/617 book also. BTW, my 70 R75/5 came with the perfect rod as part of the toolkit. (used to determine TDC on the BMW) Ok, so I've replaced the chain in my 617.910. It is now perhaps half a degree better than it was before the chain replacement, but the crank scale is still reading 15+ degrees ATDC when the cam notch is lined up with the mark! (pics attached) Given the measurement margin of error, the 15 degree offset seems suspiciously close to the 18 degree offset produced when the chain is off by one tooth at the cam. I'm wondering if it skipped a tooth at some point in the past, perhaps when the chain was replaced previously (it was an IWIS chain and had almost no wear). I know this skip didn't happen during my recent chain replacement, because at no point was either end of the chain not under tension or out of contact with the cam gear. I didn't even remove the tensioner. In any case, before I go further I need to determine whether the crank scale's indicated TDC really is TDC... Apart from the scale, is there any other externally visible reference mark on the crankshaft? I want to rule out that the harmonic balancer/scale has come loose or wandered, something that seems to happen occasionally, eg if someone impatiently reinstalled it during front seal replacement. If possible, I'd rather not have to remove a prechamber to check piston position, so I'm hoping maybe there's some kind of reference mark on the crankshaft that can be checked against the scale. And given how hard it sounds like it is to properly install the balancer once removed, I'd rather not touch that either if I can avoid it. Would removing the lower oil pan be an option as a means of seeing the movement of #1 conn rod towards TDC? I haven't checked if the pan can be removed in-situ, but intuitively it seems like perhaps it could... D. -- next part -- A non-text attachment was scrubbed... Name: %IMG_1711.JPG Type: application/applefile Size: 53662 bytes Desc: not available URL: http://okiebenz.com/pipermail/mercedes_okiebenz.com/attachments/20101105/94e64838/attachment.bin -- next part -- A non-text attachment was scrubbed... Name: IMG_1711.JPG Type: application/octet-stream Size: 910453 bytes Desc: not available URL: http://okiebenz.com/pipermail/mercedes_okiebenz.com/attachments/20101105/94e64838/attachment.obj -- next part -- A non-text attachment was scrubbed... Name: IMG_1727.jpg Type: image/jpeg Size: 1361447 bytes Desc: not available URL: http://okiebenz.com/pipermail/mercedes_okiebenz.com/attachments/20101105/94e64838/attachment.jpg ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] OM617 - Identifying real crank position
Craig wrote: In any case, before I go further I need to determine whether the crank scale's indicated TDC really is TDC... That would be a good idea. I just got home from swapping the harmonic balancer on a friend's Toyota. Last summer when he broke the timing belt, we discovered that the timing mark was about 70 degrees off from where the pistons were. Balancer looked OK, so we just slapped it back together. This week he started having accessory drive problems. The balancer had failed and the pulley was trying to chew a hole in the timing cover. The moral to the story is that if the timing mark on the balancer is incorrect, replace the balancer NOW. Mitch. ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
Re: [MBZ] OM617 - Identifying real crank position
2mm lift method? -Rolf On 11/5/2010 3:32 PM, David Bruckmann wrote: Ok, so I've replaced the chain in my 617.910. It is now perhaps half a degree better than it was before the chain replacement, but the crank scale is still reading 15+ degrees ATDC when the cam notch is lined up with the mark! (pics attached) Given the measurement margin of error, the 15 degree offset seems suspiciously close to the 18 degree offset produced when the chain is off by one tooth at the cam. I'm wondering if it skipped a tooth at some point in the past, perhaps when the chain was replaced previously (it was an IWIS chain and had almost no wear). I know this skip didn't happen during my recent chain replacement, because at no point was either end of the chain not under tension or out of contact with the cam gear. I didn't even remove the tensioner. In any case, before I go further I need to determine whether the crank scale's indicated TDC really is TDC... Apart from the scale, is there any other externally visible reference mark on the crankshaft? I want to rule out that the harmonic balancer/scale has come loose or wandered, something that seems to happen occasionally, eg if someone impatiently reinstalled it during front seal replacement. If possible, I'd rather not have to remove a prechamber to check piston position, so I'm hoping maybe there's some kind of reference mark on the crankshaft that can be checked against the scale. And given how hard it sounds like it is to properly install the balancer once removed, I'd rather not touch that either if I can avoid it. Would removing the lower oil pan be an option as a means of seeing the movement of #1 conn rod towards TDC? I haven't checked if the pan can be removed in-situ, but intuitively it seems like perhaps it could... D. -- next part -- A non-text attachment was scrubbed... Name: %IMG_1711.JPG Type: application/applefile Size: 53662 bytes Desc: not available URL:http://okiebenz.com/pipermail/mercedes_okiebenz.com/attachments/20101105/94e64838/attachment.bin -- next part -- A non-text attachment was scrubbed... Name: IMG_1711.JPG Type: application/octet-stream Size: 910453 bytes Desc: not available URL:http://okiebenz.com/pipermail/mercedes_okiebenz.com/attachments/20101105/94e64838/attachment.obj -- next part -- A non-text attachment was scrubbed... Name: IMG_1727.jpg Type: image/jpeg Size: 1361447 bytes Desc: not available URL:http://okiebenz.com/pipermail/mercedes_okiebenz.com/attachments/20101105/94e64838/attachment.jpg ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com ___ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
