How F am i? Cross threaded injector threads in prechamber
 

Hello, everything was going fine until today when taking an injector off and trying to put it back in it wont go in. I discovered the upper threads were completely gone and cross threaded. Will i need a new head?
The image is here: https://files.fm/f/g3k629z24r

Ouch! I suspect if you can locate him there is a guy out there who can fix it.

What engine is it please?

I think you could just replace the prechamber and the injector, no?

It is an OM602 engine.

How hard is it to remove the prechamber?

I have several 602 heads.
I THINK they all have prechambers that can be replaced when damaged.
I have the pc removal tool as well...

Be sure to remove the glow plug first...

First the big warning that I myself forgot. The glow plug has to be removed before the prechamber comes out.

If your prechamber retaining ring has 2 big slots for the removal installation tool the injector threads are in the retaining ring and a new ring is the fix with its new threads. And there is no absolute need to remove the prechamber from the cylinder head.

If your prechamber is splined as in the below ad the Injector threads directly into the top of the prechamber. Remember, if you remove the prechamber the glow plug is the first thing to come out.

https://www.taiwanautotools.com/Product/Detail.aspx?id=1331

From your picture you have the splined retainer and that means it is the top of the prechamber that is stripped. The puller uses the threads on the prechamber to screw the tool into to pull the prechamber out.

The question is going to be after the glow plug is removed and the retaining ring is removed if there is enough threads left to allow the forced needed on the tool to pull the prechamber.

Post number 1 has a picture of the prechamber tool and the thread sizes.
http://www.peachparts.com/shopforum/diesel-discussion/263938-question-about-precombustion-chamber-pulling-tool.html

One way to go would be at blast with an air gun to get any chips out. Put a small rage in the bottom and degrease the stripped area with brake cleaner and do the same with the proper end of the puller tool. (After the glow plug and the retainer ring are removed.) Coat the inside threads of the prechamber with slow curing JB Weld and the threads on the puller. Screw the puller in and just tighten it a bit. Give it the full cure time like till the same time next day. If it is cold out, you need to find some way to heat it to at least close to room temperature in order to cure the epoxy.

Laser Tools is an English Company that has tools made for them in China. From the ones I have used would say they tools are good quality. They are sold on US eBay.

Thread in the slide hammer, after removing the glow plug, and hammer out. Not a big deal if the threads are ok. Thing is, even the slide hammer can damage the threads. The angled injector setup isn’t great for removal. The threads are weak.

I’d chase the threads on the prechamber. And be prepared to have to cut new ones and use some kind of adapter to hammer it out.

One would think that there is a Mercedes special tool out there for the stripped thread issue. But maybe not.

It is hard to pick what to do when you are not there.

In theory if the threads were nonexistent if your adapter has long enough threaded area someone could get a skinny arc welding rod and weld it to the lip of the prechamber.

The other option is to rethread the inside of the chamber and make a puller adapter to thread into that.

Another option is removing the cylinder head and driving the chamber out.

Any cross thread or thread damage would require change of the prechamber anyway.

I have the OE MB slide hammer. Its threads are somewhat weak themselves.

When I had an un-removable head shield, and it ruined my prechamber, I didn’t have a great ability to get the hammer threaded on. I forget why but the prechamber threads weren’t great. It all worked out. If not, rethreading the prechamber would have worked. Then the new bolt thread would just need to be adapted to the slide hammer.

https://i.imgur.com/K3Rs3HEl.jpeg

https://i.imgur.com/HTlRGpll.jpeg

Might be time for a full blown automotive machine shop
 

I remember growing up; my father was a master auto mechanic. However, once in a while he required a full service automotive machine shop for a particular repair. In those days some of the NAPA auto parts stores also had a full service auto machine shop. They had expensive specialized auto machine shop equipment on the ready and they could perform just about any service you might need.

I don't know if NAPA still has these machine shops because I haven't seen them for awhile, however it might be worth inquiring about. Also, you will probably need a flat bed to tow your car to the machine shop and be prepared to leave it for a week. One thing about it, you could screw this one up to the point of no return which means you would have a very expensive boat anchor on your hands. At least a competent (check out their trust pilot and yelp.com reviews FIRST) machine shop could get you back up and running.