Tightening injectors to not leak
 

Is it possible to overtighten or damage injectors? I cleaned them out with brake cleaner and a paper towel, put new nozzles in, then tighted the halves to 80 Nm's (with a torque wrench), but there still is a slight fluid leak, even though it's very minimal. No bubbling.

Can I safely tighten them a bit more? Diesel Giant suggests having the injector casing soak submersed in brake parts cleaner.... Might this improve things? I already went meticulously with my fingernails, brake parts cleaner, paper towels, to clean the threading, but maybe having it soak will help.

Are you sure it's the injectors and not the return hoses? Did you reuse the old hoses or use new one? Old ones will often leak. If you have enough you can cut 1/2" or so off each end and reuse.

I understand the two halves must be "lapped", or made absolutely flat so you won't get a leak.

Diesel Leak At Injectors
 

I have a similar question to Tomas. About 9 months ago I had the cover off to look at the injectors and pull the fuel lines. At the time the bores the 4th and 5th injector screw into were pretyy full of fuel. I replaced all the small return fuel lines and tightened the fuel lines as best I could. I pulled the cover today and the same two were half full of fuel again. I don't think the return lines are leaking. They are new. The fuel lines seem tight. Is this a big deal? What is the likely cause/solution.

98 E300 with 280,000 and probably the original injectors. Still getting the same fuel mileage as 100,000 miles ago.

I see another post that talks about this problem: http://www.peachparts.com/shopforum/diesel-discussion/297670-99-e300d-td-om606-injector-wells-filling-diesel-not-return-lines.html?highlight=e300+injector

It is not making me crazy but I may try to get the special tool to tighten the fuel lines. If that doesn't work maybe I'll pulland injector and switch it with another. If the car were performing poorly I might just get all 6 injectors rebuilt.

Answer
 

Lapping is the critical step of getting the injector body to seal.

HOW-TO: Rebuild Diesel IDI Injectors
vincewaldon.com - HOW-TO: Rebuild Diesel IDI Injectors


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great! thanks! Didn't see that on the Diesel Giant howto.

Over Torquing the Injector Nut can cause it to split/develop a hair line crack. And, it might not happen until sometime later after the Engine Heating and cooling (when shut off) gets to work on it a while.

You are one of the unlucky ones that did not get away with swapping the Nozzles without lapping the 3 surfaces that should have been lapped.
Or you got some dirt or lint between the surfaces.

How to Rebuild Injectors
http://vincewaldon.com/index.php?option=com_content&task=view&id=20&Itemid=28

I believe you should use a real Lapping Plate or at the vary least use a Plate of Glass as your Lapping Plate instead of the Paper in the above thread.
Shops that sell Rock polishing stuff have the fine grits of lapping compound. It takes less than 1/8th if a Teaspoon of lapping powder/compound to do a whole set of Injectors. You can use Water or Light Oil with it.

Also you might consider that Diesel Giants advice in this case might lean to more of a way of selling the Injector Nozzles He sells than to doing the best job.

I purchased a set of rebuilt injectors from a well known mercedes site and I have both number 4 and 5 leaking. On emailing them I was asked if I tried "tightening the injectors halves" to which I responded with the question "I would have to remove them from the engine to do that yes?" Their response was to tell me to brake clean them very well and put a bead of blue lock-tite around and down into the threads. when I protested that this seemed a band-aid and not a proper fix, they pointed me to a "lapping kit" they sell which looked like a couple of sheets of fine sand paper and a bottle of blue lock-tite.

I have changed the return lines but I'm still getting a good amount of leakage.

Anyone have any thoughts?

You got ripped off. They should have lapped them before you owned 'em.

Also, check for any nicks on the nipples.

Lapping an injector will not guarantee that it will be leak free. And leak-free on the tester does not guarantee the same when installed.

Thanks TooMany - Still no thoughts on the Blue Threadlocker? I put some on last night, we'll see how it holds up

and I did send an email to the vendor asking if the injectors were lapped prior to reassembly, and if they'll replace them if their threadlocker suggestion does not work

Blue thread locker may work as a sealant, not sure.

The factory doesn't call for it, so you shouldn't need it.

Blue Lock-tite and new lines did not help...still spilling fuel out of 4 and 5

http://img521.imageshack.us/img521/9...dinjector5.jpg
Injector #5 (Closest to firewall)
http://img440.imageshack.us/img440/6...ctor5secon.jpg
another view of #5
http://img864.imageshack.us/img864/8...injectors4.jpg
this is injector #4
http://img441.imageshack.us/img441/8...dinjector3.jpg
On this one (injector #3) you can see the front (Left) side is dry and the body of the injector itself, down where the halves screw together, the line coming over from injector #4 is wicking fuel over.

Are those jumper lines new?

If not, replace 'em.

When I have taken my lines off and replace them they always seem to leak but the fuel always welled up around the lines where the net is. I just re tighten the lines and the leak stops. You appear to have leaks from the return lines.