Rebuilding the w123 300D injectors WITH PICS

[julian]

Hi everyone.
Some of you may be aware that I imported a bunch of Monark nozzles for the w123 diesels. I still have quite a few sets left- check the parts for sale thread for details.
I finally found some time today to dedicate to splitting a set and prepping them for new nozzles. I will post up the progress including pictures for each step of the way and for those folks looking for some more help there is an excellent pictorial here: http://vincewaldon.com/index.php?option ... &Itemid=28 with great high resolution pictures and a good explanation of the process. I am also happy to answer questions if I can so post away and if I can't answer then surely someone else can on these great boards.

The early 300D had injectors set to open/pop at 115bar, and the later more powerful cars' (post 1980 brains trust?) injectors opened at 135bar. If you are looking for a set to match your own car then this information is clearly written on the outside of the injector.

So splitting them:

Split apart.JPG

Keeping each injector's components seperate I then soaked the parts in carburettor cleaner to remove as much varnish and gunk as I could.

Some of the injectors had a thick caking of carbon deposits between them and the body of the nozzle that was so thick I had to use significant force to remove the nozzles. This was probably due to leaking/absent/used heat shields on the car these came from. A lesson to use new heat shields.
Here is what the carbon looked like on the nozzle:

A little bit of carbon.JPG

And again in the body:

And a little more.JPG

The surfaces that need to be lapped were scored and pitted, looking much like this for all of them:

A bit pitted.JPG

After a careful pass over the 1500 grit to remove the bulk of the damage I moved to the much finer 3000 grit to polish them to near mirror shine. I used sandpaper on a sheet of glass as my lapping surface, and ATF as the fluid medium. I used the ATF under the paper to keep the paper from moving around and regularly added it to the surface of the paper. All surfaces look more or less like this now:

Working away with the 3000 grit.JPG

Once I get my 27mm deep socket back from getting machined, and find a little time I will reassemble them and I can start testing them for leaking and opening pressure. Stay tuned...

[MR300TD]

Great stuff Julian, thanks for posting the process, am watching keenly :occasion5:

[chrisaus]

Did this recently with injectors I purchased from Julian. Very happy with the results! Far better idle, greatly increased acceleration (around 25%).

[julian]

With the help of Peter from Sydney (thanks mate) I now have a 27mm socket so work can proceed!

So the injectors are back together and torqued up to 55ft.lbs or 75Nm. Once they reach the engine the same torque specs will be used for tightening them into the head.

Reassembled.JPG

Next job will be to pop test them. This will be as much a test of my pop tester as anything else: viewtopic.php?f=5&t=15229

Stay tuned.

[julian]

So with the help of DieselJames from ozbenz I attacked the 300D today. The car has never enjoyed a cold idle and today I found out why.

We removed the hard lines to access the injectors, cut away the brittle old leak lines and pulled the injectors to find this:

Old nozzle erosion.jpg

This shows the long term damage that can occur to the face of the nozzle, made no better by the fact that there were no heat shields on the car. These are essential to protect the nozzle from the harsh combustion environment as well as provide a malleable seal. All of the old nozzles were equally eroded.
When we put the old set on the pop tester they opened around 1100psi (very low) with a stream of liquid fuel rather than a spray. They also dripped and could not hold pressure.

We then put the new set on the tester and had them all popping around the 1750psi mark. The fuel was vaporised with a lovely spray and we had them chattering nicely with that characteristic sound. Action shots of this are hard for us curbside mechanics but this gives you an idea of the ascent to the pop pressure:

Pumping.jpg

Everything went back together nicely, with new heat shields and leak lines. I'll check the hardlines after a week of driving to make sure that there are no sustained leaks.

The new nozzles make the car quite different. Definately a little quicker but the gains are more in the smoothness of the drive. There is no more knocking that was likely coming from poor fuel atomisation from the old set.
The thing I am most impressed with is the lack of smoke. We'll see how the economy works out over the next weeks.

[julian]

A few days later and the car is behaving very nicely. No smoke still. In the future I would play with pop pressure more to balance them together for a smoother idle. Winter starts will bring this out the most but until then I'm very happy!

[300Dman]

I have the Monark Nozzles in My Mercedes and even though not made for them I put them in My Volvo 244Gl Diesel.

I have read the Vince walden Injector Rebuild Instructions. There is another alternative as to what to use for a Lapping Plate.

I used a Plate of Glass with 600 Grit Lapping Compound. The Aluminum Oxide Compound comes as a dry powder and can be mixed with light Oil or Water.
I got it on eBay from a Seller who sells stuff for tumbling/Polisning Rockes. There is likely some stores that sell it but it is a small item and the shipping cost was small; saving Me a drive.
Way back around 1975 I worked in a Fuel Injection Shop and they used 500 Grit lapping Compound on the Injectors so that is the reason I chose the 600 Grit as I knew it would work.

So I have lapped 3 sets of Injectors on the Glass Plate with no leaing issues. Later after watching and bidding on ebay I bought a real Lapping Plate at a decent price but have not needed to use it yet.

When rebuilding the Injectors it is a good idea to keep all of the Parts from one Injector together. This is a big help when it comes to setting the opening/Pop Pressure.

Also If the Previous Owner had replaced the Injectors You might find that Your Engine has 2 Types of Injector Bodies. And, as long as the Injectors have the correct Pop Pressure the different type Injectors can be used on the same Engine.
However, internal parts of the different types of Injectors should not be interchanged because they have different dimensions. Another reason to keep all of the parts of an Injector together.
The pic shows the 2 types of Injectors/Bodies.

[Bartman4800]

Julian,

Before you use that pump again:

Please read a reply I left on your other topic: viewtopic.php?f=5&t=15229
If you insist on using it again, keep your hands away from any of the connections.


Bart

[300TDT]

I'm about to replace my nozzles.

Does anyone have any left-over shims that they don't need? Happy to pay.

[leighsha]

I have just recently done the same using Bozio injectors. Runs great now. :)

[julian]

Great work mate. What were the before and after symptoms?

Thanks?
Julian

[leighsha]

Before it was blowing smoke and running rough. Now no smoke and runs smooth

[julian]

Great work.
Where did you source those Bozio nozzles?

[timtams]

awesome detail and effort on the post.

being a small business owner in sydney I'm quite time poor, is someone here interested in doing mine or can you point me in the direction of who i should go to. Im sure there is plenty of info here on the forum which i am slowly sorting through as this is my first day here.

i have a W123 300d with about 340k kms on the clock

thanks in advance

[mathuisella]

Just thought i'd include a bit on the injector front.

Before
https://www.youtube.com/watch?v=UdeRmIUI4pE

cleaned with old nozzles
https://www.youtube.com/watch?v=a0Fbeg-X6A8


clean + new nozzles

https://www.youtube.com/watch?v=RzE7D4bCnZM