For those who have rebuilt/lapped injectors....

[300SD90]

I have began lapping my injectors to remove surface marks to prevent leaks. I am having a hard time getting the center of the intermediate disc free of any marks. There is a ring where I believe the spring sits, and I cannot get it clear even with 600 grit sandpaper.

Should I keep going at it or leave it as it is? Hopefully you can see what I'm talking about from the pictures.

Edit: I was also wondering if the injectors need to be tightened to spec when I pop test then again.

Thanks!

[tjts1]

Switch back to 2000 grit. Wet sand with light pressure in a circular pattern until it becomes somewhat reflective. You're only concerned with the inner and outer edges of the surface. The area in between doesn't matter. You will have to torque it to spec before pop testing again. Your first pic needs some more work, second looks fine. Keep in mind that the longer you're sanding the higher the pressure is going to be.

[Diesel911]

Get some 600 Grit I think it was Aluminum Oxide powder that I bought from a Rock Polishing Vendor on ebay. Or buy it locally from a Lapidary (spelling?) Shop.

Or you can use what ever grit you want.

Use plate of Glass as your lapping plate and use the grit with water as a lube.

A light weight Oil line 3&1 Oil or Sewing Machine Oil or Lighe weight Gun Oil is nicer to use but requires something like Solovent or Brake cleaner to clean it off.

If you use Water it is cheap and easy to clean off but you need to blow the part off with compressed Air and get it quickly into Diesel Fuel or light Oil so it will not rust.

I have done the above using a Glass Plate on 5 sets if Injectors. Since then I bought a real Lapping Plate but have not used it.

Vince Walden how to rebuild IDI Injectors.
http://vincewaldon.com/index.php?option=com_content&task=view&id=20&Itemid=28

[crazy4diesel]

Send them to Greezer. ;-) That's what I did.

[300SD90]

I would have sent them to Greezer if I had known about him prior to building a pop tester and buying all of the parts needed to rebuild the injectors! Wish I would have known but it's good to know how to do them anyway.

Diesel911, I have been doing it that way but I cannot seem to get the middle of the injector to a mirror finish. I am simply wondering if that small ring in the second picture is okay and will not cause any leaks.

[greazzer]

Hey,

If you want my .02 cents ...

I would try to find new intermediate disks. "Normally" if those disks are truly cleaned, one will end up with a perfectly machined surface. I generally avoid "lapping" since either the disk is toast OR you have a leak elsewhere. I have never successfully gotten rid of a leak by lapping and I have done well over 1,200+ injectors. That is, the leak is always because of something else or the disk is messed up so just swap it. I have lapped them to get rid of WVO caked on crap, but that was a cleaning issue and not a leveling issue.

[300SD90]

Would I need to find used injectors to source the intermediate discs? If the injectors do not leak during pop testing, is this a good sign that they will not leak when installed in the engine?

[Diesel911]

Originally Posted by 300SD90

I would have sent them to Greezer if I had known about him prior to building a pop tester and buying all of the parts needed to rebuild the injectors! Wish I would have known but it's good to know how to do them anyway.
I bought 600 grit because that is what was selling at a resonable price.

Diesel911, I have been doing it that way but I cannot seem to get the middle of the injector to a mirror finish. I am simply wondering if that small ring in the second picture is okay and will not cause any leaks.

I don't know what to say on that. I used to work in a Fuel Injection Shop and there we used 500 grit lapping compound and a real lapping Plate on all kinds of Injectors and we always lapped them.
So My experience reflects how I was taught to do them.

500 grit does not produce a mirror finsh. It produces a dull sort of light mat gray finish. 500 grit also removes more metal Faster that something like 1200 grit does.

Keep in mind that where I worked we had to warrant what we did so if our proceedure did not work the resulting loss of Money and pissed off Customers would have forced a change in Proceedure.

But, there ia likely more than a few People that dissagree with the above method.

Also I personally don't think any sort of Abrasive Paper that you can buy at the Auto parts store is as flat as a Plate of Glass or of couse a real Lapping Plate. But, People who have followed the Vince Walden thread seem to have made it work.

What is not being said is that usually a fuel leak between the upper and lower Injector Bodies does not show up on the Nozzle/Pop Tester. It shows up after it is on the Engine and subjected to heat, vibration and the pulsation of the Injected Fuel.

Then everyones experience is different. More than a few People who did the Diesel Giant Nozzle Swap have ended up with at least one leaking Injector. It is not possible to tell if that is due to something getting between the parts or from them not being lapped.

I guess you will have to find something that works for you.

[300SD90]

I started with 600 grit then moved my way to 1200 then 2000, and lubed the sandpaper with motor oil.

I guess my main question is, should I continue lapping with 600 grit until that small inner ring is gone? I am worried about removing too much metal, but I do have plenty of shims to adjust pop pressure.

[greazzer]

In response to what Diesel911 said, if the injector parts are truly cleaned to near surgical percision, then the intermediate disk will have what appears to be a perfectly flat, shiney machined surface sort of like a mirror. And yes, folks lap them all the time and so have I but it's generally lapping to clean them, not erase gouges. I use 800 grit then 1000 grit sandpaper. You can find that at WalMart in their automotive section by 3M. However, I suggest if you can source good intermediate disks, I would go that route.

[Diesel911]

Originally Posted by greazzer

In response to what Diesel911 said, if the injector parts are truly cleaned to near surgical percision, then the intermediate disk will have what appears to be a perfectly flat, shiney machined surface sort of like a mirror. And yes, folks lap them all the time and so have I but it's generally lapping to clean them, not erase gouges. I use 800 grit then 1000 grit sandpaper. You can find that at WalMart in their automotive section by 3M. However, I suggest if you can source good intermediate disks, I would go that route.

I understood what you said before and like I said some People are going to disagree with Me. It is just infomation offered for People to make their own choice.

[greazzer]

Originally Posted by Diesel911

I understood what you said before and like I said some People are going to disagree with Me. It is just infomation offered for People to make their own choice.

Yup, I agree with that 100% !!!! I was not actually disagreeing with you in a technical sense.