So, for a while I've complained about my injectors leaking. I've replaced the return lines several times, and that has not helped. A year ago, I pulled the injectors and put new nozzles and heat shields in. That is when the injectors began to leak. Now, on ********, I see this part...

http://www.***************/search/product.aspx?sid=sin13halvyz4rxnl0ba4z3n2&makeid=800016@Mercedes&modelid=1193802@300DT&year=1987&cid=22@Fuel%20%26%20Air%20System&gid=6232@Fuel%20Injector%20Seal

And I'm wondering what that is (that is, the first two items, not the one pertaining to the IP). I've never heard of this thing, and I surely did not use it on my injector job. Any insight? I'm this close to purchasing six new injectors, I'm sick of not knowing what the problem is. Thanks!

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1987 300D wvo on the way!

The two items in the picture are for the delivery nozzles on the IP, not the injectors (on the head).
These (esp the rubber Oring) are what let air into the system and allow the pressures to vary across the lines and the result is pronounced nailing especially on a cold start.
Its common to have a slight air bubble on an Injector, if you have a lot of fuel leaking on the head from the injectors you may need to torque then properly, I forget what 50 nM? not sure. Or the lines may be leaking where they fit the input to the injectors, these should not be overtorqued as they will leak if the end gets cracked.

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!

Well, fuel appears to leak from the middle of the injector and the base (perhaps it is just the middle). Some bubbles also appear at the base. Perhaps I didn't tighten the two halves of the injectors enough? Perhaps I didn't torque the inectors hard enough? Perhaps the heat shields were defective???? I want to avoid having to pull the injectors several times (on my 603, it is a rather huge and very frustrating job), so any advice and all troubleshooting is welcomed.

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1987 300D wvo on the way!

You had the injectors apart??? That's really not for the uninitiated.

From the description it seems the second part in that list is an o-ring internal to an injector.

70Nm ~ 52 lbft

Heat shields go between the injector tip and the prechamber. A fault in this seal will cause a compression leak, not a fuel leak... certainly not a fuel leak that will puddle.

Sixto
87 300D

I suppose I will clean off the injectors tomorrow and determine exactly where the leak is coming from. I'm 99% sure that it is not the hoses. Everytime I've conducted a visual "test," I've concluded that the injectors leak at the middle. Has anybody had any experience with injectors leaking at the middle? Thanks!

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1987 300D wvo on the way!

So yeah, the leak is without a doubt coming from the middle of the injectors. It is most intense on the #3 injector, but they all eventually leak after a bit of driving. Should I just buy all new injectors? I mean, what could I possibly do to stop the leak?

I'm going to pull all of them in the next day or two. Wish me luck!

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1987 300D wvo on the way!

I fought this issue with the 4th injector for approx 2 months even replaced the injector to no avail. Turned out to be, in fact, the return lines! If leaking it will show in the middle of the injector and bubble in the recess. Look at the nipples the lines go on for scrape marks from someone slicing off the old lines. Use a magnifying glass. Use crocus cloth to clean the nipples. Use only brown woven MB hose. In rare cases the hard line can have a hair line crack at the flare which can seep. Also the hard lines MUST not be bent where they rest on the injector. The retainer nuts should spin down very easily with your fingers then chinched with a wrench. Also are all retainers than span across the metal lines in place? Many times they end up discarded. Missing retainers allow the hard lines to vibrate and crack.

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81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.

I would throw $10 worth of OE braided return hose at it before touching the injectors.

If it's indeed the injectors, look for a Bosch shop to clean and balance them. That should include resealing the midsection.

You can take the injector apart yourself but you risk changing the spray pressure and pattern settings... to where you were better off with a leak.

Sixto
87 300D

I already tried replacing the return hoses, it didn't work. Today I fired up the car for the first time in a while and I watched the injectors, and the fuel was surely coming from the middle. There was no wetness abbove the middle of the injector, so I am SURE that it is not the return lines (believe me, I wish it was.) Sixto, is there really a sealant that goes between the two halves of the injectors? If I have a Bosch shop balance the injectors, will they "reseal" them without me specifically asking them? (in other words, is a reseal part of the "balancing" job?)

Carnut, one of my fuel lines has to be slightly forced into place or else it won't line up with the injector. However, the line shows no signs of a crack. Believe me, I thoroughly inspected for wetness. I just pulled the intake and the hard lines, and nothing seems suspicious. Also, you said that leaky return lines would cause leakage from the middle? Wouldn't there be some wetness up towards the top of the injector if the return lines were really responsible?

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1987 300D wvo on the way!

I don't know that there's a seal. Job 07.1-232 describes reconditioning injectors and there's no seal in the parts diagram. I know that they take the injector apart to clean it and replace shims as part of the balancing job... and it better not leak when they give it back :/ But I'd tell them before hand that I suspect it's leaking.

Sixto
87 300D

So, after reading a bunch of old posts about leaky injectors, I'm starting to think that I over tightened the two halves of the injector bodies, which apparently have a lapped thread? I did not use a torque wrench when tightening the two halves together (oops), will this have damaged the injectors? Or will I be able to pull them out and retorque them? I really hope that this is all there is to my leak problem.

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1987 300D wvo on the way!

Back when I was convinced it was an injector leaking, I simply went to a pick n pull and grabbed an injector with the same series number on it. The wreck had no signs of a prior leak. After replacement it still was damp at the middle because the ledge where the two halves meet collects the fuel from the seeping return hose. In ten years of ownership I never had a reason to take apart an injector. But in ten years I replaced return hoses and the end plug probably 3 times for seepage. The hard line that you say must be forced should be slightly bent back to easily thread on. This line should be looked at with a magnifying glass for a hairline crack at the end that rests on the injector. If the line does not seat square to the injector it could deform the flare end on the hard line and seep. I ask again, are the retainers in place between the return lines?

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81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.

Some of the retatiners are in the place. There are a few rubber pads here and there, and I have (had) two of the seperating clips in place. But seriously, it is not the lines. I have checked thoroughly. It wouldn't make sense because there is absolutely no moisture towards the top of the injector.

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1987 300D wvo on the way!

Completely clean off the injectors with brake clean and allow to dry. Sprinkle on baking soda to cover the line fitting and injector body. Start the engine and verify the source of leak.

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81 300CD (sold) 1972 280 SEL 4.5 (sold) 1966 250 S 4 spd (sold) 1974 450 SL (sold) 86 BMW 325ES (sold), 1973 280C (sold) 1988 300 SE.

Talc (baby powder) works well also, as does foot powder in a spray can.

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Gone to the dark side

- Jeff