1987 300D Leaky Injector - PeachParts Mercedes-Benz Forum

iamtheosprey · #1 06-23-2014, 04:24 PM

Ok, I detected a fuel leak a few weeks ago but I figured it was the return lines.

I replaced them but the leak is back because I smelled fuel.

So, I start up the engine and see bubbles of air/fuel coming from the base of the rearmost injector.

My question is whether I can just tighten the injector or do I need to do something else?

Also, if I can just tighten it what size socket or special tool do I need to execute that?

winmutt · #2 06-23-2014, 04:46 PM

It all depends on which part of the injector. body? bottom? top?

vstech · #3 06-23-2014, 04:58 PM

In my experience, when they bubble, the motor is hot, and the return line or plug is soaking the injector and heat is bubbling the fuel. No leaks found on my cars' injectors yet

iamtheosprey · #4 06-23-2014, 05:30 PM

Quote:

Originally Posted by vstech

In my experience, when they bubble, the motor is hot, and the return line or plug is soaking the injector and heat is bubbling the fuel. No leaks found on my cars' injectors yet

After checking everything out very closely I agree with you.

My problem is that even after using new hose three different times on the plug side it still is leaking.

I noticed that the nipple has an indention on the upper surface and it spins around in the injector freely.

How the hell do I keep it from leaking?

Diesel911 · #5 06-23-2014, 08:47 PM

Quote:

Originally Posted by iamtheosprey

After checking everything out very closely I agree with you.

My problem is that even after using new hose three different times on the plug side it still is leaking.

I noticed that the nipple has an indention on the upper surface and it spins around in the injector freely.

How the hell do I keep it from leaking?

You just diagnosed your problem.
The Nipple is Press Fitted into the Injector Body then an circular Crimp is applied around it. While occasionaly they come loose all on their own it sounds like yours was the Victim of a Socket that did not fit right. I say that because you sed the Nipple was dented on one side.

One of our Members came up with the fix. You remove the Injector and cut off the Nipple Part and have someone weld over and seal the Area. Then you move that Injector to the last Cylinder where you have one Injector that normally has the Nipple Plugged off.

The other fix for it is to replace the upper Body of the Injector. However that means taking the Injector apart, lapping the Precison surfaces, replacing the upper Body and then having it Pop Tested.

Get another good used Injector and replace the leaking one.

I have never gotten anyone to try this (and I have never had the problem Myself to have to try it) so I don't know if it would work or not. At they hardware Store they sell low temp Silver Bearing Solder.
I think that if you follow the Instrctions that come with the Solder and use it might be possible to get the silver solder to wick into the clearence between the Nipple and the upper Body and seal it.
If that worked you would still be left with a dented Nipple that the Hose might not seal on.

You would need a Propane Torch or a smaller Butane one might be better.

vstech · #6 06-23-2014, 11:01 PM

I don't think I would use a propane torch on a spring operated precision device like an injector...

I do think I would try spraying brake cleaner on the nipple, blast it dry with compressed air, then dribbling loctite green on it sparingly...

iamtheosprey · #7 06-24-2014, 01:16 AM

Quote:

Originally Posted by vstech

I don't think I would use a propane torch on a spring operated precision device like an injector...

I do think I would try spraying brake cleaner on the nipple, blast it dry with compressed air, then dribbling loctite green on it sparingly...

Good suggestion.

I think this fits my skill set better.

iamtheosprey · #8 06-24-2014, 01:17 AM

Quote:

Originally Posted by Diesel911

You just diagnosed your problem.
The Nipple is Press Fitted into the Injector Body then an circular Crimp is applied around it. While occasionaly they come loose all on their own it sounds like yours was the Victim of a Socket that did not fit right. I say that because you sed the Nipple was dented on one side.

One of our Members came up with the fix. You remove the Injector and cut off the Nipple Part and have someone weld over and seal the Area. Then you move that Injector to the last Cylinder where you have one Injector that normally has the Nipple Plugged off.

The other fix for it is to replace the upper Body of the Injector. However that means taking the Injector apart, lapping the Precison surfaces, replacing the upper Body and then having it Pop Tested.

Get another good used Injector and replace the leaking one.

I have never gotten anyone to try this (and I have never had the problem Myself to have to try it) so I don't know if it would work or not. At they hardware Store they sell low temp Silver Bearing Solder.
I think that if you follow the Instrctions that come with the Solder and use it might be possible to get the silver solder to wick into the clearence between the Nipple and the upper Body and seal it.
If that worked you would still be left with a dented Nipple that the Hose might not seal on.

You would need a Propane Torch or a smaller Butane one might be better.

I had considered pulling the injector but I don't think I have a tool that would do it.

Is there a special tool or will a normal deep well socket work?

Diesel911 · #9 06-24-2014, 11:51 PM

Quote:

Originally Posted by vstech

I don't think I would use a propane torch on a spring operated precision device like an injector...

I do think I would try spraying brake cleaner on the nipple, blast it dry with compressed air, then dribbling loctite green on it sparingly...

Apparently a quick Arc Welding over the cutoff Nipple does not effect the Spring.

The Sliver Solder I was speaking off needs the localized Metal to be at 720 degrees F. I don't have My Heat Treating Book handy but I believe when you make a Spring you do what is needed to harden the Metal and then subject it to high tempering heat. A heat that is higer than 720 degrees F; meaning that that temp would not effect a Spring.

If you heated up Steel that was Hardend and not tempered to 720 degrees F that would change the Hardness a bit.

iamtheosprey · #10 07-10-2014, 12:55 AM

Sorry it took me so long to update...but here it is:

I got the green permaseal/loctite.

I removed the return lines cleaned the injector with brake cleaner, used a McDonald's straw to blow off excess brake cleaner and through the nipples on the injector to make sure it was all completely dry.

I then applied the green thread locker to the base of the nipple.

First time, I let it set for a few minutes then wiped excess off.

I then let it set for an hour or so then re-installed the return lines.

Next day the leak was still there.

Second time I cleaned it all off the same way but this time I just put the thread locker on there until there was a nice puddle over the leaky nipple.

I placed a rag around the injector to keep any of that stuff from making it's way into the injector threads or anything else I may have to replace someday.

I let it sit this way overnight (about seven hours) then removed the excess thread locker with a rag.

I did it this way because I remember reading that this stuff won't cure in an oxygen-rich environment. It needs to be sealed from air.

The little bubble was still there and still very liquid.

I reinstalled the return lines and my leak has disappeared.

Diesel911 · #11 07-10-2014, 11:47 AM

Quote:

Originally Posted by iamtheosprey

Sorry it took me so long to update...but here it is:

I got the green permaseal/loctite.

I removed the return lines cleaned the injector with brake cleaner, used a McDonald's straw to blow off excess brake cleaner and through the nipples on the injector to make sure it was all completely dry.

I then applied the green thread locker to the base of the nipple.

First time, I let it set for a few minutes then wiped excess off.

I then let it set for an hour or so then re-installed the return lines.

Next day the leak was still there.

Second time I cleaned it all off the same way but this time I just put the thread locker on there until there was a nice puddle over the leaky nipple.

I placed a rag around the injector to keep any of that stuff from making it's way into the injector threads or anything else I may have to replace someday.

I let it sit this way overnight (about seven hours) then removed the excess thread locker with a rag.

I did it this way because I remember reading that this stuff won't cure in an oxygen-rich environment. It needs to be sealed from air.

The little bubble was still there and still very liquid.

I reinstalled the return lines and my leak has disappeared.

Good deal you may have discovered a good repair for that issue. Besure to come back in 6 months or so and let us know if the repair lasted.

I don't know what is available now but back in the 1980s the Green Loctite was one that you could drop onto already assembled Nut and Bolts and it was supposed to wick into the clearances between the Nut and Bolt.

In the places I worked we only used the Blue and Red Loctite.