Well, I got my fuel injectors reassembled, but unfortunately, three of them leak.

I did the lapping procedure and I also made sure they were nice and clean. I also blew them out with compressed air.

Yet, two of them at least are leaking at the return nipples and three are leaking at the body joint.

Will these leaks tend to seal themselves with time?

Since the nipples are not serviceable, does that mean a new fuel injector is required?

Also, one other problem. There is no fuel coming from the No 1 line. I removed it to blow compressed air through it and it is clear, there is fuel at the pump end, but no fuel comes out the other end.

Thanks

Mark

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1975 300D

Will these leaks tend to seal themselves with time? Nope

Since the nipples are not serviceable, does that mean a new fuel injector is required? Yup, assuming that the leak is coming from the nipple and not coming from the return hose

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I would suggest sending them off for service to forum member Greazzer. He has helped me out tremendously in the past and does a fantastic job. There may also be other members that offer the service in your area.

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Examine the Nipples for bbnds and damage like nicks or scratches. If you see none replace the Injector Fuel Return Hose and see if that fixes the leaks.
If the Fuel Return Hose is farily new try cutting off about 1/4" of the Hose and see if that helps.

If it turnes out the Nipples are leaking around where they are pressed into the Injector you only need to change the Upper part of the Injector Body. However, that changes the Pop Pressure of the Injectors.
Also used Injectors at the Junk Yard used to be under $10 each in my area.

It is unusual but the Injector Nuts can sometimes develop hair line cracks; especially if they are over tightened.

You did not say what you used to lap the parts?
Vince Walden how to rebuild IDI Injectors.
http://vincewaldon.com/index.php?option=com_content&task=view&id=20&Itemid=28

I dissagree with the lapping method in the above thread but a lot of people have used it and had good luck.

I have built several sets of Injectors using a Glass Plate as a Lapping Plate and using 600 Grit Aluminum Oxide lapping/polishing compound I bought from a Seller on eBay that sold rock polishing stuff (Lapidary I think it is called).

Some People have said that 600 Grit is too coarse that it should be 1200 or higher. But, where I used to work we used 500 Grit daily.

Since that time I bought a Real Lapping Plate but have never built any more Injectors so it is unused. I mention that only to indicat how important I think Lapping is.

Story Time. I go for walks and I found what was left or a small portable Halagon Shop Light. I used the Glass Lense as a Lapping Plate.

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84 300D, 82 Volvo 244Gl Diesel

HI, I used a glass plate for lapping. Started at 400, went to 1000 and then to 1500.

The return hoses were brand new.

Up here in Canada, we have no vintage cars in wrecking yards. In my wrecker yard, all the cars are about 15 years old, and I have yet to see a Mercedes in there. It's just Japanese and American and Korean.

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1975 300D

They Sell used sets of Injectors on eBay but they are not going to be $5 each.
Also that "Running Pull" comment the Sellers put in their Ad is meaningless. When your Injectors were worn the Engine was also likely running.

Unfotunately there is no way to test for the leaking Fuel Return Nipples on the Pop Tester.

Down here in the US the Hardware Stores sell Silver Bearing Solder that melts around 750 degrees Fahrenheit. I have never tried it but it might be possible to remove the top of the Injector and use a small Butane Torch to heat up the Body under the Fuel Return Nipple and drip on the Flux and apply it to the base of the Nipplen and see if you can wick some of that down inside.

For that to work the Body has to be nice and hot otherwise you will end up with a blob on top.

Even regular Solder used for Electrical work might work for a time but I think the Diesel Fuel may eat it up eventually.

You might also swap positons of the Injector to see if it leaks in another spot. If the leak stops when you move the Injector to the other spot I would suspect that for some reason the Fuel Injection Hard Line is not seating well in the Injector.

The ends of the Fuel Injection Hard Lines on mine seem to be made of Metal that does not deform easily. But, I have seen Fuel Injection hard Lines on other Diesels where over tightening the Line Nuts had resulted in a dented ring on the end of the Fuel Injection Hard Line or had spread the end of the Injector out.

To tell if that is where the leak is coming from you need to degrease it good start the Engine and get there fast with a strong Flashlight to see if you can spot the leak.

My choice is to run My Finger under the Fuel Injection Hard Line Nut. If it is wet there that is not likely coming from the Return Hoses.

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84 300D, 82 Volvo 244Gl Diesel

Okay, thanks for your advice.

The first thing I will do is remove the leaking ones, and clean out the hole where they go into better.

Then remove the halves and reclean them again.

Then maybe try to solder the nipples.

BTW, does the return hose have to totally to the bottom of the nipple or will it leak?

Also, does pivoting the nipples cause leaks?

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1975 300D

Couple things I noticed in your last post:

- Be sure to replace the heat shields when you replace the injectors. These are single use washers and must be replaced if they have been torqued.

- The return hose needs to seat all the way on the nipple.

- The nipples should not be able to pivot.

- I highly recommend Greazzer, he has done 2 sets of injectors for me, and does excellent work.

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Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech

Hey Bob,

The nipple on one injector was right up against the body, so no hose could be put on it. So I was able to rotate it away from the body.

If I don't replace the head shields, will the diesel leak from the bottom, or from where the two halves join?

I replaced all the heat shields but I notice I have diesel pooling at the bottom too. Can dirt there cause the problem?

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1975 300D

None of the Return Nipples are supposed to be able to rotate. The Nipples are pressed into the Upper Injector Body and then a circular Crip is appplied over the edge
The Heat Sields have nothing to do with Diesel Fuel leaking between the upper and lower 1/2 of the Injector.

Concerning the Pooling. Between where the Injetor seals on the Heat Shield and the theads on the Injector there is an empty space between the Injector and the Injector Nut. Fluid from an external source can seep into the empty Space past the Threads on the outer Injector Body; that includes Fuel from a Hose leak and Oil from Valve Cover Gasket leaks.

When Fluid gets in that space and the Engine is running it appears to bubble out. But actually I believe what seems to be bubbles from a leak is actually the Fluid being moved by the shock/vibration of the Injection.
A lot of People mistake a Heat Shield leak for the above mentioned leak.

If the Nipples were bent agaist the Injector Body the Injector was dropped or damage was done by a Socket that was not deep enough. Some 6 point Sockets even when deep enough will Hit the Nipples and scratch or bend them.

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84 300D, 82 Volvo 244Gl Diesel

Thanks

You say the empty space between the injector and the injector nut. Where is the injector nut? You mean the nut on the line?

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1975 300D

Hey fellow CANADIAN I'm out west Calgary and have a few injectors I pulled from a 81 300d if you are in need. Actually this is the first time I ever ran across a 300 d in a recycle yard. I'm working through some injectors myself and believe I finally understand the procedure fully now.

Hi Diesel Benz, thanks for the offer. I am going to try to see if I can stop the leaks today at the nipples. If not, I might need a couple of your injectors.

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1975 300D

You might also look at the recyclers for vw diesels 80's early 90's they use a similar injector but you would have to be real lucky to find bosch many had installed Italian or French injectors and different springs so you would have to play around some to set them up right,

See the pictures.

Attached Thumbnails

   

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84 300D, 82 Volvo 244Gl Diesel