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  #17  
Old 05-27-2009, 06:54 PM
scottmcphee's Avatar
1987 w124 300D
 
Join Date: Mar 2008
Location: Edmonton, Canada
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Ya he said reamed.

But did you blow the debris out of the hole after that, i.e. are the glow plugs not seating well enough in their holes. Lowering compression.

I just replaced my GPs (BERU it turns out... not knowing when PO did them last) and put in Bosch. The BERU came out nicely.. and of course they all tested great, glowing hot and long. These may be years old with lots of miles of service on them... and still going strong. Anyway..

A few of the Bosch went in FIRM inserting them through the hole before the threads met up. I did not ream the holes. I thought that was awfully tight, not allowing for expansion of that metal and taking them out later with carbon on them.

Am I doomed when I go to get them out?
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  #18  
Old 05-27-2009, 07:13 PM
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Ok.. did you use heavy grease when reaming them out ?
Perhaps some carbon fell into the precombustion chamber ?
Better not to blow into that area... better to vacuum...
and using the movement of the pistons sure has the potential for pulling carbon flakes into the precombustion chamber...
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  #19  
Old 05-27-2009, 07:33 PM
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leathermang and scott

Thanks for the replies. Yes, I reamed out the holes with a "special glow plug carbon reamer tool" that I bought from another online source (I'm an idiot for tools). Anyway, there seemed to be a fair amount of build up, but this was my first effort at reaming GP holes, so I have no comparison.

I tried to do more vacuuming than blowing, and even bought (here we go again) a nozzle attachment for my old Sears shopvac in an effort to remove the old carbon. The nozzle was still too big, so I don't know if it did much good.

I guess what I'm getting at is that I'm o.k. with how things are now after the full glow cycle. Again, this is my first diesel, MB or o/w, so I don't have any comparison. I suppose I had hoped that when I replaced the plugs and relay, it might glow-up, turn over, and crank right up, in a time-frame similar to a gasoline car, for example. However, this may just be the way an older diesel behaves.

Thanks for your thoughts.
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  #20  
Old 05-27-2009, 09:48 PM
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Quote:
Originally Posted by Ross Davis View Post
Roberto, it certainly could be a fuel problem. I have had the "hard lines" off at least 4 times over the last month, between replacing the injectors and then fiddling around with these GPs. While my cold starts are just as rough as when I would first crank after replacing all injector lines, my warm starts and on-the-road running/idle/etc are all pretty smooth. As a trial, I might try your WD40 suggestion though.
If you've run it to warm I wouldn't expect air in the lines to be a problem. Unless you've got another issue with air in your fuel lines. But your warm starts would indicate that this is not the case.

Quote:
Originally Posted by Ross Davis View Post
Ryan Z, good point. I should have been more clear, but I do think that I have 12 volts at each GP. With GPs out of car, and key in "glow" position/position 2 (?), I got 12 volts at each harness-GP connection (the terminal from the harness that connects to each GP).
You need to check the voltage at each glow plug with the plugs installed and connected. When the system is cold, have the meter ready under the hood, have someone turn the key to number two. Ground the black lead of the meter and use the red lead to measure the voltages at each GP. You should actually see 13-14 volts under load. If you have a loose connection or broken wire, it will drop the majority of the voltage across that rather than the glow plug, i.e., you will see a much lower voltage at the glow plug. If you have a low voltage at all the glow plugs, your GP fuse may be loose or corroded. Your battery seems to be good if you can glow for 25 secs and crank it to start.
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  #21  
Old 05-27-2009, 11:26 PM
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Quote:
Originally Posted by micalk View Post
You need to check the voltage at each glow plug with the plugs installed and connected. When the system is cold, have the meter ready under the hood, have someone turn the key to number two. Ground the black lead of the meter and use the red lead to measure the voltages at each GP. You should actually see 13-14 volts under load. If you have a loose connection or broken wire, it will drop the majority of the voltage across that rather than the glow plug, i.e., you will see a much lower voltage at the glow plug. If you have a low voltage at all the glow plugs, your GP fuse may be loose or corroded. Your battery seems to be good if you can glow for 25 secs and crank it to start.
13-14V ??? Not gonna happen. The battery voltage of a fully charged battery is under 13 volts. The glow plugs draw a lot of current, and the normal resistance of the battery cables and terminals will drop the voltage at the glow plugs down well below 12V and that is normal.
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  #22  
Old 05-28-2009, 10:40 AM
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1987 w124 300D
 
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You'll actually notice that glow plugs are rated at less than 12v.
The Bosch I put in are rated at 11v, stamped right on it. This is obviously intentional, probably indicated they work as indicated at the lower voltage to accommodate less than perfect battery charge conditions.
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  #23  
Old 05-28-2009, 11:06 AM
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Quote:
Originally Posted by scottmcphee View Post
You'll actually notice that glow plugs are rated at less than 12v.
The Bosch I put in are rated at 11v, stamped right on it. This is obviously intentional, probably indicated they work as indicated at the lower voltage to accommodate less than perfect battery charge conditions.
That is correct. I have a Bosch 603 and a Bosch 606 glow plug in front of me; both are rated at 11.5 volts as stamped into the metal. The high draw of several cold glow plugs will pull even a new battery down below 12 Volts. As the glow plugs heat up, their resistance increases and they draw less current, thus allowing the voltage to rise a bit. When you energize the starter, the voltage will drop further, so it's important to get the plugs good and hot before turning the key all the way to the start position.

Jeremy
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  #24  
Old 05-28-2009, 11:21 AM
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Quote:
Originally Posted by Ross Davis View Post
...........I guess what I'm getting at is that I'm o.k. with how things are now after the full glow cycle. Again, this is my first diesel, MB or o/w, so I don't have any comparison. I suppose I had hoped that when I replaced the plugs and relay, it might glow-up, turn over, and crank right up, in a time-frame similar to a gasoline car, for example. However, this may just be the way an older diesel behaves..................
I agree that new glow plugs, reaming and injectors should improve starting. However, there are several other factors, besides glow plugs, that will affect starting. A current valve adjustment will be another item you will want to check out. Also, engine timing will be another major factor.

From reading your first post, did you install new heat shields with your rebuilt nozzles? I'm not sure how much effect it will have but did you also use a torque wrench and torque the injectors? Did you run a couple hundred miles after reinstalling the injectors before changing glow plugs and the relay? All of these may factor in to smoother starts/running.

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