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  #16  
Old 02-13-2014, 10:35 PM
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Quote:
Originally Posted by vstech View Post
OP, the picture you linked to does show the metal resistor wires, so that engine has loop glow plugs.
a good glow plug reamer would help, but replacing them all with pencils would help more.
if the motor has not been tuned recently, the valves would certainly benefit from the attention!
In the site I looked at it had Wires going from one Glow Plug to another but they appeared to be insulated.

On My Volvo the Pencil Type Glow Plugs were wired in Series Parallel. Meaning that all the terminal ends were connected in series to a Wire that has the Positive Voltage but the individual Glow Plugs are grounded in Parallel to the Cylinder Head.
(This is the same setup that people do when the install the Adapter Pencil Glow Plugs to replace the Filament/Loop type Glow Plugs.)

In that system one Plug can go bad and still not cut the electricity to the rest. But to test an individual Glow Plug you need to disconnect it from the Terminal Wire.
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Last edited by vstech; 02-14-2014 at 10:12 AM.
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  #17  
Old 02-13-2014, 10:42 PM
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Originally Posted by Barginginfrance View Post
Any suggestions as to where I might get a good quality reamer? I guess the thread has to be the same as the glow plugs?
You would also need to know what size the reamer needs to be.

I don't see why Stainless Steel Rifle or Shot Gun Bore Brushes would not work.
On My own Engine after the Reaming is done you are supposed to tie or hold the Fuel Injection Pump Throttle Lever in the Shutoff Position and crank the Engine and it blows out any loose Carbon particles the fell into the Precombustion Chamber.
If you hold the Lever in the Shutoff Position and have someone else crank the Engine be sure to protect your Eyes; even if the minimun you do is to close your Eyes.

You would also need a section of Cleaning Rod to mount the Brush on.
SHOTGUN BRUSH SIZES; threaded end 5/16x24 inches in the USA.
Diameters of the Brushes.
10 gauge 0.775"
12 gauge 0.729"
16 gauge 0.662"
20 gauge 0.615"
28 gauge 0.550"
410 bore 0.410"
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  #18  
Old 02-13-2014, 11:53 PM
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I thought the parts circled in the Pic were the Glow Plugs.
Attached Thumbnails
OM321 starting problems (1992 barge in france)-mercedes-engine-om321-jan-15.jpg  
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  #19  
Old 02-14-2014, 12:36 AM
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D911-
The OP has stated that the GPs are loop GPs, so they must be in series. The photo he posted also appears to have a ground wire from the last GP to the block. Also, I don't think the parallel pencil GP had been invented yet when his engine was made. So maybe that photo that you found is of an engine which has been retrofitted with pencil plugs.

To the OP-
Those pencil GPs were designed to retrofit into the same hole as the old loop GPs. So assuming your loop GPs are the same as later loop GPs (1960s), those pencil plugs would work just fine. But how many times per day do you start your engine? If it is only once or twice, I would say that upgrading to pencil plugs in parallel isn't really solving anything. Who cares if once or twice per day you save 20 seconds running the GPs?

If definitely sounds like you need to ream your holes. An earlier post of mine in this thread had a link to threads where I give the dimensions of the reamer. So if you are on a budget, get a drill bit of similar size and mark it to ensure you don't go in too deep. I will PM another option as well.

And adjusting the valves, as has been suggested, would be good use of your time. Good luck.
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  #20  
Old 02-14-2014, 10:33 AM
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Quote:
Originally Posted by Shortsguy1 View Post
...
To the OP-
Those pencil GPs were designed to retrofit into the same hole as the old loop GPs. So assuming your loop GPs are the same as later loop GPs (1960s), those pencil plugs would work just fine...
This is a bit of an assumption - the OM321 seems to originate from the 1950s and according to findpart.org the Bosch glow plugs of what we speak appeared in diesel vehicles from 1959 onwards =>

BOSCH 0 250 001 016 (0250001016) Glow Plug

They might be close cousins - they might be same - they might not. I can't find much information about the OM321 out there on the interweb.

The specifications for the glow plugs that MIGHT be the same are here =>

https://www.bosch-automotive-catalog.com/public/catalog/products?p_p_id=BoschWSRP&p_p_lifecycle=1&p_p_state=normal&p_p_mode=view&p_p_col_id=column-1&p_p_col_count=1&_BoschWSRP_wsrp-urlType=blockingAction&_BoschWSRP_wsrp-navigationalState=%2FWFS%2FAAGLOBAL-AA-Catalog-Site%2Fnl_NL%2F-%2FEUR%2FViewSearchProduct-Detail%3Bpgid%3DD41D8CD98F00B204E9800998ECF8IS7qrzXw%3Bsid%3Dul2b0DfTYl2TkWUtj8kXKjhYmvJYN_zt2Z0%3D&_BoschWSRP_proxyportlet-remoteInvocation=true
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Don't leave that there - I'll take it to bits!
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  #21  
Old 02-14-2014, 12:33 PM
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Quote:
Originally Posted by Barginginfrance View Post
Thanks for your replies. A picture of an OM321 6 cylinder diesel can be seen here and you can clearly see the glow plugs below the direct injectors.

http://www.machinetrack.be/construction-machinery/parts/motors/1378220420951-36-2/mercedes-benz-om-321.jpg

Everything was working perfectly until a year ago. Started first turn every time......
The OM321 was built with direct injection and indirect injection with prechambers.
Are you sure which version you have got?

How many hours are on the old nozzles? When was the pop pressure and spray pattern checked last time?

Gruß
Volker
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  #22  
Old 02-14-2014, 12:55 PM
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Quote:
Originally Posted by Stretch View Post
This is a bit of an assumption - the OM321 seems to originate from the 1950s and according to findpart.org the Bosch glow plugs of what we speak appeared in diesel vehicles from 1959 onwards =>
That preheating.pdf document that I linked to in my second post describes how the older (1950s) GPs are different than our "modern" loop GPs. It describes how the oldest ones used some short of spiral filament (capable of handling 1.4 volts), versus the round wire loop that we are more familiar with (capable of handling 0.9V). It does not say that the threads were different, nor the overall dimensions being very different, which is why I made my assumption. So yes, it is a bit of a leap of faith since that document I found discusses only the om621 and om636, but the era is the same so it is not too unlikely that MB would re-use the same prechambers, gps, etc.
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  #23  
Old 02-15-2014, 02:44 AM
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Quote:
Originally Posted by Shortsguy1 View Post
That preheating.pdf document that I linked to in my second post describes how the older (1950s) GPs are different than our "modern" loop GPs. It describes how the oldest ones used some short of spiral filament (capable of handling 1.4 volts), versus the round wire loop that we are more familiar with (capable of handling 0.9V). It does not say that the threads were different, nor the overall dimensions being very different, which is why I made my assumption. So yes, it is a bit of a leap of faith since that document I found discusses only the om621 and om636, but the era is the same so it is not too unlikely that MB would re-use the same prechambers, gps, etc.
Well if the OP is so inclined the thread diameter and pitch is specified on the Bosch site I linked - may be he'll be so good as to tell us how he gets on?
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Don't leave that there - I'll take it to bits!
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  #24  
Old 02-15-2014, 02:49 AM
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Quote:
Originally Posted by volker407 View Post
The OM321 was built with direct injection and indirect injection with prechambers.
Are you sure which version you have got?

How many hours are on the old nozzles? When was the pop pressure and spray pattern checked last time?

Gruß
Volker
I'm interested in where you got this information - I've been struggling to find out more (so I'm not being argumentative - just inquisitive). According to this link they all had pre-chambers

Mercedes-Benz OM 300 (klein)

It might be wrong though 'tis after all wikipedia(!)
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1992 W201 190E 1.8 171,000 km - Daily driver
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1965 Land Rover Series 2a Station Wagon CIS recovery therapy!

Don't leave that there - I'll take it to bits!
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  #25  
Old 02-15-2014, 04:22 AM
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Quote:
Originally Posted by Stretch View Post
I'm interested in where you got this information - I've been struggling to find out more (so I'm not being argumentative - just inquisitive). According to this link they all had pre-chambers

Mercedes-Benz OM 300 (klein)

It might be wrong though 'tis after all wikipedia(!)
As the thread starter said in post #10

OM321 starting problems (1992 barge in france)

he has direct injection on his engine.

I did remember that on a research about the OM321V I found out that Mercedes tried several 100 engines with DI instead of IDI.
So I thought maybe the thread starter has an engine with direct injection that survived until now.
Although I think it is most likely a prechamber engine.

Here is some information about it with pictures.
The birth of a legend: the 300 engine series, first unveiled in 1949, is a major advancement | Daimler Global Media Site > Classic > Daimler AG > Technology

Gruß
Volker
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  #26  
Old 02-15-2014, 08:08 AM
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Originally Posted by volker407 View Post
As the thread starter said in post #10

OM321 starting problems (1992 barge in france)

he has direct injection on his engine.
But also from post 10:
"The glow plugs have a small wire loop that glows and once inside, resides in a small pre chamber."
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  #27  
Old 02-15-2014, 08:17 AM
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Quote:
Originally Posted by volker407 View Post
Although I think it is most likely a prechamber engine.

Here is some information about it with pictures.
The birth of a legend: the 300 engine series, first unveiled in 1949, is a major advancement | Daimler Global Media Site > Classic > Daimler AG > Technology

Gruß
Volker
That article discusses all of the 300 series engines, not just the 321. Based on a quick scan of that article, it appears that the DI engines got different numbers (om352). This is a line from the article which references the DI engines introduced around 1964 "The new units soon gained an excellent reputation and replaced the OM 312, OM 321 and OM 322 precombustion engines".

As you said, the OPs OM321 is likely an IDI engine.
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  #28  
Old 02-15-2014, 08:57 AM
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Great link thanks - I've downloaded it for a bit of bed time reading!
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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!

Don't leave that there - I'll take it to bits!
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  #29  
Old 02-15-2014, 09:04 AM
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Quote:
Originally Posted by volker407 View Post
As the thread starter said in post #10

OM321 starting problems (1992 barge in france)

he has direct injection on his engine.

I did remember that on a research about the OM321V I found out that Mercedes tried several 100 engines with DI instead of IDI.
So I thought maybe the thread starter has an engine with direct injection that survived until now.
Although I think it is most likely a prechamber engine.

Here is some information about it with pictures.
The birth of a legend: the 300 engine series, first unveiled in 1949, is a major advancement | Daimler Global Media Site > Classic > Daimler AG > Technology

Gruß
Volker
The glow plugs for these engines will probably use an 18mm thread.

I know this because I measured the thread of four glow plugs I got that were wrapped in packaging dated 1939. Apparently, they were for a 260D Benz taxi (??).

There's a German company named Beru that makes glow plugs and spark plugs. They have this cage filament glow plug.

Don't know if they still make them, but I have seen these in the past two years, so they might be able to be procured in Europe, where people don't dispose of things as readily as here.
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