I have an 85 123 and am planning to change glow plugs and ream the carbon out. While I have changed glow plugs on a previous 123 without removing the hardlines, since I recently had my injectors(extra set) refurbished by greazer , I'm thinking that it would be a good time to both at the same time.

I have a question about the bleeding process. I have read and seen that most just crack all the lines and with the glow plug relay disconnected crank the engine until fuel is seen from the injector lines. Then tighten the lines. But, I have also read about "self-priming". I'm not sure what that means. I have also read about doing one line at a time. I don't see how this would be an acceptable way as it would put excessive strain on the starter as well as possibly draining of the battery. Does anyone have an explanation as to which method is preferable?

Also, since I am doing this by myself with no assistance, would I need to have to use a remote starter? And if so how do I set up the remote starter?

Sorry for the long post. Any help or ideas is greatly appreciated.

Thanks
Charlie

I never unplugged the GP relay, just pumped the primer pump with the nuts at the injectors cracked until I felt some pressure. Then I would try to fire it, if it did not fire then crack each of them until seeing fuel at each injector while cranking. I always pulled the hard line, as you get more room and not a big issue getting the air out. A couple minute process, after changing GPs. A touch of WD40 after reaming before installing new GPs. BTW I hope you don't have Autolite GPs for the replacements.

I just put it back together and crank with the pedal down until it takes off. Usually 10-20 seconds.

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'82 300CD
"Pearl", the very first turbo diesel 123 coupe
Totaled 11/23/18, rebuild in progress.
'85 300TD, "Artemis".
'78 300D euro, "Ol' Red", mostly retired.
'85 300D, "Gandalf".

On an 85 123 if you remove the Fuel Injection Hard Lines you can tighten them at the Fuel Injection Pump and leave the nuts screwed on loose at the Injectors. Hand priming won't help to get the air out of the Hard Lines. Crank until you see fuel coming out. And crank till you see fuel coming out of them.

After that if you want to tighten the ones that you see fuel coming out of that is OK because when you crank again it may start and for sure starting would get fuel to the other Hard Lines you have not tightened.

I more often crank till I see fuel out of all of them but if I am in a hurry I have used the other method. Your choice.

The only bugger to the above is that you can sometimes have some fuel left inside of the hard lines and it appears there is sufficient fuel coming out but in fact it was just what was left in the line and there is an air bubble that still needs to be worked out. If that happens you simply have to loosen the Fuel Injection Hard Line Nuts at the Injectors and start again.

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84 300D, 82 Volvo 244Gl Diesel

Southstar ;

You're idea is great, don't forget to stuff a folded light color towel down between the block and IP to catch and dropped tiny nuts / washers .

Hold the wire ends as you loosen & tighten the too, they're easy to twist off the eyelets .

Once it's all buttoned back up you'll need to use the hand primer, if it has a white top you'll need to unscrew it until you feel the threads click before pumping it 20 times or so then re tighten it fully before you attempt to start the engine .


The black top primer pump takes more pumping, you'll fee it when the air is gone by increased resistance as you push down .

It certainly will do the job, after cycling the glow plugs crank it and KEEP THE STARTER RUNNING until all five cylinders are firing and the engine sounds like it's running away ~ it can't, not to worry, the high RPM's will bleed out the other four injectors in 30 seconds or so .

Don't panic, this is routine service done daily ~ no need for a remote starter .

I did this on the dirtiest 300SD I've ever touched yesterday after doing a valve adjust (all tight valves and many were zero clearance) and injector pop test and replace .

Easy - Peasy, don't be afraid .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Thank you so much D911 and Nate.

I do have a question, what happens to the carbon after you've reamed them?

I just recently adjusted my valves, so I'm hoping that by doing these two jobs I can get better fuel mileage. I've been getting around 21 mpg. I think that is kind of on the low end. Am I right about that?

Thanks
Charlie

There are two ways to deal with the carbon :

Cheap fast ad dirty : use the reamer dry then crank the engine with the glow plugs out and hopefully all the loose carbon will blow out and not get trapped in the upper piston ring lands .

Most shop rats and DIY'er do this and get away with it .

You're supposed to coat the reamer's flutes with oil or light grease and clean it after each pass then crank the engine to blow out any remaining carbon .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

First time I've ever heard this. Makes sense.

I've just got to ask:
> Would a "pass" mean after each complete turn?
Or
> Would a "pass" mean after completely reaming a single glow plug hole?

Maybe a dumb question but heck, here goes:
Assumption: I have only 1 glow plug removed and have just finished reaming.
Question: If I used a vacuum hand pump and pulled vacuum at the port on the back of the injection pump, could I thus withhold fuel and keep the engine from starting while I blow the debris out of the glow plug hole?

You could, but why? Removal of the glow plugs will prevent the engine from firing since the compression will be venting through the glow plug threads.

Removing all of the glow plugs will spin the engine faster with less strain on the starter motor.

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“Whatever story you're telling, it will be more interesting if, at the end you add, "and then everything burst into flames.”
― Brian P. Cleary, You Oughta Know By Now

You're supposed to lubricate all cutting thread chasing tools, always .

A pass means completely screwed in and then back out again ~ DO NOT just forcefully crank it all the way in in one go ! .

Turn it in and whenever it begins to bind, back it out a 1/2 turn and try again .

If it gets really hard to turn, stop and remove the tool, clean it, re lube it and go again .

Yes, you *could* hold the IP in the stop position and crank it to blow out only one hole but why ? .

? Are you only going to ream one glow plug hole ? .

There's lots you've not yet heard / learned, don't worry ~ I've been a Journeyman Mechanic for decades and I'm still learning daily .

-Nate

Thanks for the clarifications.

Since your injectors are out, you should be able to look down the holes and see the pre-chambers and glow plugs. I know I could in my 1984 300D. Don't recall in my 1985 CA (either OE or replacement 1982 engine). I recall it was earlier engines which had a throat in the pre-chamber which restricted the view. I just ran a regular metric tap thru the holes, but didn't pick up significant carbon on the tap, and the prechambers looked clean. I could see the tap coming into the prechambers. Since then I haven't worried about carbon. Indeed, I changed a bad glow-plug this morning and its threads were clean. I coat glow-plug threads w/ anti-seize and can unscrew them w/ 2 fingers once loose.

Re getting the air out. The hand pump is to purge air from the IP inlet. It builds pressure to pop the pressure relief valve on the IP inlet to send fuel back to the tank (I think). Unlikely you got any air in that system unless you changed a filter. I would just leave the glow-plug relay in. If the engine idles, that is better for purging. Just crack the fitting at the top of each injector until fuel dribbles out (not much at idle) and close it while running or cranking. 17 mm wrench I recall. Once purged, that is also a way to verify that each cylinder is contributing. It should run rougher as you disable each by cracking the nut. If you need to crank from under the hood, just pop the top on the little plastic terminal block in front of the battery and jumper from the front screw (cabin "crank" to solenoid wires) to either of the rear screws (same) or BATT+ (which those screws are).

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

This is a homemade glow plug reamer I used to make. When I tested it as in the pic I used Vaseline to trap the carbon so the carbon would show up. I normally use wheel bearing grease. Also the Vaseline while good for the photo is a bad choice as it gets runny at a lower temp then the wheel bearing grease.

After reaming with all of the glow plugs out I cranked the Engine to blow out any loose carbon. That is OK and it has to do that in the Mercedes Service Manual.

The last pic is not mine and I edited it. The text in the pic is from who took the pic. Apparently still getting carbon out of the hole on the third ream and using some sort of red colored grease (the wheel bearing grease I have is red).
The grooves/flute on the factory made reamers are straight.

Attached Thumbnails

   

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84 300D, 82 Volvo 244Gl Diesel

Thanx ! .

? Are the factory reamers also sans threads ? .

Red grease is that synthetic boat trailer wheel bearing / CV Joint grease IIRC, $pendy but very good stuff .

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-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Food for thought...

If the cylinder being worked on is on the intake stroke which is very possible, debris will be pulled in to the cylinder not blown out. It may and likely will be blown out later through an exhaust valve on compression strokes.

If the injectors are out, ream the holes with grease on the reamer as per the factory procedure and then blow compressed air into the injectors opening to blow debris out of the glow plug hole.

If compressed air isn't available adapt a small hose to a vacuum and vacuum the reamed glow plug hole.

Good luck!!!

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"Rudeness is a weak man's imitation of strength" - Eric Hoffer