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MikeHowe
09-05-2013, 02:39 PM
2003 T1N 3500 sprinter 143k miles...

I won't bore you all with the weekly problems I have had with my van, suffice to say that I have yet another problem I would love your thoughts on as I am determined to get some trouble free miles out of it even if it kills (and bankrupts) me...

1. Driving home from a festival at the weekend, after 100 miles stopped for a break and noticed diesel fuel had sprayed from the overflow pipe at the end of the injector valley all the way underneath the van to the rear axle.

2. Removed the injector cover to find that all the wells around the injectors were full of clean, fresh fuel.

3. Did my research on this site and found 2 relevant threads which seemed to point to leaks from the fuel return line and/or the plastic nozzles on top of the injectors.

4. Removed all the excess fuel with tissues and ran the engine to look for leaks. Couldn't see anything at all around the injector heads, return fuel line, high pressure nozzles on side of injectors.

5. Couldn't see any other obvious wet patches indicating leaks on any of the nearby fuel lines or connections.

6. Decided to drive the van with the cover off and, after a couple of miles, stopped to check, and sure enough there was fresh fuel in the wells, and the excess was running down the overflow pipe and dripping on the ground. By the way there is no chuffing from the injector seals indicating the beginnings of black death - believe me I know what that sounds and looks like.

7. For info - last week I had the #1 injector replaced (following stalling and a subsequent leak off test). The replacement was all done correctly taking care to apply the correct torque on the new stretch bolt. The high pressure nozzle connection is new. All fittings are secure.

8. I've revved the engine to 2500 rpm at stand still in order to try and see a leak, but cannot see one anywhere. It's only when I drive the van (and therefore can't look in the engine) that the fuel mysteriously gathers in the wells (the wells around the #4 and #3 injectors seem to gather the most fuel).

9. Question - where are the places this fuel could be leaking from? Is it possible that, although I can't see any wetness or drips from the connections on top of the injectors, or from the return line, that these could still be the source? Could fuel be welling up from the injector without making the chuffing noise or showing signs of air bubbles?

It is most strange. I went to the garage this morning so that they could look and they too could not find the leak. But nevertheless, clean fuel keeps gathering in the wells from somewhere. Should I just change the fuel return line and see what happens?

If anyone can list the only possible sources of the leak in this area of the engine I would be most grateful. Thanks,

Mike

Aqua Puttana
09-05-2013, 02:59 PM
I haven't tried this.

Maybe tie pieces of rag around all the high pressure fittings and go for a short drive. If fuel is leaking from one of those then the rag should be wet. Good luck. vic

MikeHowe
09-05-2013, 03:13 PM
I haven't tried this.

Maybe tie pieces of rag around all the high pressure fittings and go for a short drive. If fuel is leaking from one of those then the rag should be wet. Good luck. vic

Thanks Vic (as always), that is a very bright idea, I shall try that. Any other suggestions welcome. Mike

Aqua Puttana
09-05-2013, 04:13 PM
...
If anyone can list the only possible sources of the leak in this area of the engine I would be most grateful. Thanks,

Mike
I didn't really answer your question.

Raw clean fuel would be almost impossible to come from a leaking injector seat seal unless the engine were running rough. A leaking injector seat seal can reduce compression, but the "black death" goo that builds up is a product of combustion gases escaping.

To my knowledge about the only places for raw fuel to be leaking in that area would be the return line or fuel rail fittings. It is possible for a pinhole leak to develop in either system, but suspect fittings first. If the rags on the high pressure fittings don't reveal anything then the rags could be moved over to the return line fittings in a similar manner. Be careful with those return fittings. They can be a bit delicate. vic

surlyoldbill
09-05-2013, 04:21 PM
It's gotta be the return fuel lines, I'd check the #1 first since it was recently messed with. Maybe the return line wasn't put back on very well, or there is an o-ring missing or something. Compare the #1 fitting to other fittings to see if something is missing or different.

Aqua Puttana
09-05-2013, 04:28 PM
It's gotta be the return fuel lines, I'd check the #1 first since it was recently messed with. Maybe the return line wasn't put back on very well, or there is an o-ring missing or something. Compare the #1 fitting to other fittings to see if something is missing or different.
Good point.

If any high pressure fittings were loosened or tightened without using two wrenches (one for fittiing backup) then a fitting itself could be loose. vic

Boater
09-05-2013, 10:44 PM
Inspect the rubber hoses on the return assembly, the ones on my sprinter seem to be good, but on my diesel vectra (and all diesel vectras) the ends develop fine cracks over time where they are pushed onto the fittings - can be near impossible to see but allow air to get into the fuel system and prevent starting on a vectra - if air can get fuel can probably get out under pressure. Also if you have the plastic push in return fittings, they can crack, unfortunately MB only sell the entire assembly not individual fittings, but if it is just hoses you can get diesel leak off pipe from most factors. Mine has miniature brass banjo fittings instead of the plastic type but I think they were only on very early sprinters.

NORTON
09-06-2013, 06:42 AM
It's gotta be the return fuel lines, I'd check the #1 first since it was recently messed with. Maybe the return line wasn't put back on very well, or there is an o-ring missing or something. Compare the #1 fitting to other fittings to see if something is missing or different.

As they are secured by clips maybe they were not seated properly, remove all and clean and check all connections.

MikeHowe
09-06-2013, 07:01 AM
Thanks to everyone for some very good advice and ideas for pinpointing the problem. I shall now go out and do some testing and, just so you know I very much appreciate the time you've taken to reply, I will post my findings. Mike

MikeHowe
09-06-2013, 09:15 AM
Ok so I've completed experiment number 1. I attached some tissue around the return line fittings and the high pressure nozzle fittings (see photos - ignore the black crusty areas, they are left over from a massive black death clean up from a year ago and yes I did put the main cover back on before I set off) and went for a short drive...

After I had travelled 3 miles I stopped and checked for leaks....nothing. So I drove another 3 miles (van is now up to normal operating temperature) and checked....

The wells around #3 and #4 injectors (far end) had a good amount of clean fuel in them and the #1 and #2 wells were dry. I examined all of the tissue wraps I had made and they were all bone dry.

There is absolutely no evidence of fuel running into the wells from higher up in the direction of the fuel rail and high pressure pipes, and all of the lines connecting to the fuel rail are bone dry. I cannot understand how clean fuel is very quickly appearing in the wells around the injectors but there is no sign of dampness on any other area or on any of the lines and fittings. The fuel return line itself appears to be bone dry, but nevertheless fuel is leaking from somewhere.

I should now check the individual return line nozzles but I can't understand how, if they are the source of the leak, the tissues I wrapped around and underneath them were dry?

Obviously I'll keep hunting but if anyone can suggest any other possible source of a leak that eventually fills all of the injector wells with clean fuel? The only other clue I can give is that the garage did a leak off test 2 weeks ago (to diagnose a stalling problem which resulted in #1 injector being replaced and problem solved) so perhaps the return line fittings are leaking but I'm blowed if I can see how and from where?

Boater
09-06-2013, 11:02 AM
How do the return lines connect to the injectors?
Some I have seen are a plastic fitting with an O-ring on that are held in by a spring clip, just thinking if the clips are tired or the o-rings damaged/worn could the fuel be escaping under the rags without soaking into them?
I think your rags have probably ruled out slpit hoses looking at how you have wrapped them round.

Is there wet on the brather valve?

MillionMileSprinter
09-06-2013, 12:24 PM
Hmmmm. This shouldn't be a tough one, but it's proving difficult to pinpoint.
Did you check to make sure your fuel return line isn't clogged in some way?
I would drive the van around until it starts leaking again and then get a helper to rev the engine while you sit and watch it.
Or maybe if you had a video camera that you could mount inside the engine bay to watch the injectors, you could record it while you drive.
Good luck.

Boater
09-06-2013, 12:42 PM
Another job for a Gopro!

MikeHowe
09-06-2013, 01:52 PM
I have to admit I am totally baffled. When the engine is idling there is absolutely no leaking and nothing untoward to be seen. So I've just done a series of small test runs and I have found that the #4 injector well fills first and subsequently spills into the others because of the van movements back and forth. When enough builds up in the well it overflows down the pipe at the back of the head.

So I'm pretty certain that the leak is coming from the area of #4 injector (at the back of the engine bay). I've used more rags around the high pressure nozzle and the return line nozzle, and they are always dry - the fuel appears in the well without touching them. I have removed the return line nozzle and carefully re-seated it, even applying a tiny bit of grease around the o-ring, which looks ok but of course may not be, but then why isn't there any wetness around the return line nozzle or drips down the side of the injector?

If the return line is blocked in some way, and causing the leak, surely I would be able to find where it was leaking out? Like I say, all the connections, sides of the injector valley, pipes etc are all bone dry. All except the well which fills up with clean fuel from somewhere.

If I didn't know any better I would say that the fuel is welling up (excuse the pun) into the well from around the injector base. Is this possible? How are the injectors secured in the head? Is there a seal at their base that could be compromised?

Does anybody have a view on this, and also why does the leak only occur when driving but never during idling? Clearly this is pressure related so does this rule out the return line (which appears to be fine)?

I'll keep looking. The van starts better than ever since the #1 injector was replaced and I got rid of the WIF sensor on the fuel filter which was letting in loads of air. The van runs very well, so whilst this issue isn't critical (at least I hope not), it isn't very nice having diesel spraying out the back from the overflow pipe whilst driving, it's all a bit smelly and a bit of a fire hazard no doubt.

Thanks all for your thoughtful suggestions, please keep them coming. :thumbup: Mike

ps I've been to the garage and revved the engine whilst the mechanic peered everywhere for signs of the leak - no joy, he's as mystified as I am.

Aqua Puttana
09-06-2013, 02:01 PM
So it seems to be around #2 and #3 injectors?

Maybe take some pieces of pad paper cardboard (at least our USA pad paper still uses that) and cut them so that they can be inserted in a half roll down beside #2 and #3 injector well. Any fuel that contacts the cardboard shouldn't spread very quickly and may leave a trail for you to follow.

It may be a pinhole in an injector body or some other relatively rare problem.

Nice idea with the tissue paper. Was it wrapped tight enough to absorb a drip? There may or may not be a spray. vic

Your injectors are basically the same design as this OM647 injector body.

54407

Boater
09-06-2013, 09:42 PM
The only way I can see you would have raw fuel forced up past the injector seal is if you have no ignition at all on that cylinder, so first does it sound right or is it misfiring? If it is firing you would have exhaust gas being forced up around the injector seal - you already had black death so know something about where that leads!

To answer your question about they are held in, the injector body is smooth sided so the only thing that holds the injector in is the clamp and bolt you see on top of the head. At the bottom of the injector between the body and the seat is a copper seal.
Now, when your black death was cleaned up the seat should have been re-cut to make sure it would seal properly, and of course a new copper seal should have been fitted. A copper washer crushes slightly to make the seal, I have known someone cut a corner and not buy the correct seal, turned out the copper washers he used were copper plated steel and didn't seal properly at all!

NORTON
09-06-2013, 10:02 PM
Perhaps the injector body is leaking from its joins for assembly, change it with the front injector and see if the leak follows.

MillionMileSprinter
09-06-2013, 10:11 PM
So how about you get the van warmed up (I mean fully warmed up because I'll bet the leak is heat related as in when something heats up and expands, then it starts to leak- you could even put the injector cover on with two screws to keep the heat in and get it a bit hotter), then put on the parking brake, then hold down the brake pedal with your left foot, make sure you have 4x4 chocks in front of the wheels, put the tranny in "D" and rev the engine with a load on it. You could even secure the rear end to a parked car with a rope to be really safe.
This would simulate a load on the engine, but someone can stick their head under the hood and watch if any fuel squirts or leaks out.
Be careful that you don't overload the tranny!
Good luck.

NS215
09-06-2013, 10:26 PM
this company do the leak off pipe and fittings, both plastic and brass much cheaper than MB, never used them but very good feedback on ebay
http://www.ebay.co.uk/itm/281069294876?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Boater
09-08-2013, 12:17 AM
So how about you get the van warmed up (I mean fully warmed up because I'll bet the leak is heat related as in when something heats up and expands, then it starts to leak- you could even put the injector cover on with two screws to keep the heat in and get it a bit hotter), then put on the parking brake, then hold down the brake pedal with your left foot, make sure you have 4x4 chocks in front of the wheels, put the tranny in "D" and rev the engine with a load on it. You could even secure the rear end to a parked car with a rope to be really safe.
This would simulate a load on the engine, but someone can stick their head under the hood and watch if any fuel squirts or leaks out.
Be careful that you don't overload the tranny!
Good luck.

I don't like that idea, maybe try it on a rolling road, or the brake test rollers at an MOT station?

NORTON
09-08-2013, 03:40 AM
So how about you get the van warmed up (I mean fully warmed up because I'll bet the leak is heat related as in when something heats up and expands, then it starts to leak- you could even put the injector cover on with two screws to keep the heat in and get it a bit hotter), then put on the parking brake, then hold down the brake pedal with your left foot, make sure you have 4x4 chocks in front of the wheels, put the tranny in "D" and rev the engine with a load on it. You could even secure the rear end to a parked car with a rope to be really safe.
This would simulate a load on the engine, but someone can stick their head under the hood and watch if any fuel squirts or leaks out.
Be careful that you don't overload the tranny!
Good luck.

I was under the impression that the pressure in the injection circuit was constant under all engine loads.
Mike did any of the injectors have to be dis assembled to be removed?

MikeHowe
09-08-2013, 10:44 AM
I was under the impression that the pressure in the injection circuit was constant under all engine loads.
Mike did any of the injectors have to be dis assembled to be removed?

Thanks all for chipping in with good suggestions. I can't answer that question about injector dis-assembly until I speak to the mechanic again, but from my experiments and observations the fuel seems to be leaking into the #4 injector well from somewhere around the injector itself.

Having determined that the fuel leak was coming from that area and then spilling into the other injector wells whilst driving, I wondered whether the fuel return pipe at the far end, where it turns right toward the fuel rail, might have a hole or crack in it. So I wrapped more tissue around that part of the pipe and went for a drive.

After a couple of miles (engine not quite up to normal operating temperature) I could see no fuel in the injector well or any other sign of a leak. After a further 3 miles I looked again - fuel in the #4 injector well, and the tissue I'd wrapped around the whole back end of the return pipe was bone dry!

I could see that some fuel had spilled over the ridge and into injector #3 well.

So my observations so far are...

1. The fuel only appears after a few miles driving but does not appear to be flowing from any of the fittings or pipes around the injector (all of the tissues wrapped around every conceivable fixture have been bone dry.

2. The engine runs fine with no mis-firing and no chuffing noise coming from the injector.

3. At idle, when peering into every crevice of the area in question, using torches, mirrors etc..there is absolutely no indication of where the leak is coming from.

4. The ONLY place where fuel appears is around the base of the injector, which would suggest to me, that fuel is escaping from the injector itself somehow, but I'm not sure if this is possible.

5. As far as I am aware the garage used all of the correct procedures to re-install the injectors into the brand new head cylinder following the horrendous black death episode. I know for a fact that they used the copper washers and brand new stretch bolts. Could the injector have been damaged in some way during it's removal from the old head? Not enough to affect engine firing and running but enough to cause a leak of raw fuel?

This is one of those cases where I'm sure at any moment I'm going to spot the leak and then feel like an idiot, and I've reached the point now where I'd love that to happen, but I just can't see it (and neither could the garage mechanic).

I'll keep looking, and tomorrow I shall question him about the injector. All I know for sure is I only started noticing this leak after they did the leak off test and replaced #1 injector, which is not the place where the leak is coming from.

Thanks for all the suggestions, I shall keep you posted, even if the answer turns out to be embarrasingly obvious!

SullyVan
09-08-2013, 10:55 AM
Leak is coming from #4, but they replaced #1: Wouldn't be the first instance I have heard where a mechanic broke something else trying to fix something.

MikeHowe
09-08-2013, 03:48 PM
I just had the van idling for 45 mins on the driveway, I was virtually in the engine with a bright torch and a mirror, no sign of a leak absolutely anywhere. Then took it for a short drive....clean fuel appeared in the #4 injector well.

So this confirms (although I knew already) that the leak only occurs at what I am assuming are higher pressures whilst the van is being driven.

Does anybody know what this could mean (given all the evidence presented so far)? Is there a weep hole at the back of the injector where fuel could be leaking out during driving pressures? Could the fuel escape from the injector at some point like that? The connections (high pressure and leak off) are all bone dry and apparently sound. The injector segments are all dry apart from the ones at the base where the fuel gathers.

I'm going to leave it and have a think before I decide what to do next. I don't have the tools or knowledge to take the injector out, I'd have to take it to the garage again and I'm reluctant to do that because it's been in there for most of this year with one problem after another...Mike

Aqua Puttana
09-08-2013, 05:32 PM
... The connections (high pressure and leak off) are all bone dry and apparently sound. The injector segments are all dry apart from the ones at the base where the fuel gathers.
...Mike
The high side fuel system pressures I recall are higher at engine operating speed than they are at idle.

If my memory is correct, there is another joint down deep by the injector nozzle.
54449

All I can think is to repeat my earlier suggestion of pad paper cardboard.

If you had the means to swap injectors around then moving the #4 injector to another spot as was mentioned already would be another idea.

vic

MikeHowe
09-08-2013, 06:12 PM
The high side fuel system pressures I recall are higher at engine operating speed than they are at idle.

If my memory is correct, there is another joint down deep by the injector nozzle.
Edit: That joint would see less volume at idle than while running. If leaking there, it will take longer at idle to fill the well.

54449

All I can think is to repeat my earlier suggestion of pad paper cardboard.

If you had the means to swap injectors around then moving the #4 injector to another spot as was mentioned already would be another idea.

vic

Thanks Vic, I will try your cardboard suggestion. I still can't quite believe that I can't see the leak in one of the more obvious places, but no matter how long I look, I see nothing.

I've had one other thought I'd like your opinion on. I know there is potential danger of tightening the hold down bolt too much because of washer crushing and breaking the bolt, but what would happen if it wasn't tight enough? The garage reset the injector and bolt when the new head was put in, and I don't know for certain that they used the correct torque (7nM plus 90 degrees). I'm learning that to assume such things isn't always the best policy. If it wasn't tight enough, would fuel potentially be able to well up at the higher running pressures you suggested above?

I don't have a torque wrench but I could take it in for testing. Is that a possibility or another red herring? Would love your (or anyone else's) thoughts on that. Thanks, Mike

Aqua Puttana
09-08-2013, 06:29 PM
...

Edit: That joint would see less volume at idle than while running. If leaking there, it will take longer at idle to fill the well....
vic


Note that I deleted my edit about squirts. The chamber down near the injector nozzle is always under pressure. The needle moves to let that pressurized fuel out in squirts. Number of squirts shouldn't matter if the nozzle joint is leaking, but higher fuel pressure in that chamber could affect a leak.

54407

...
I've had one other thought I'd like your opinion on. I know there is potential danger of tightening the hold down bolt too much because of washer crushing and breaking the bolt, but what would happen if it wasn't tight enough? ... Thanks, Mike
Please do not mess with your injector hold down bolts. There is no way I can imagine that the raw fuel can be coming from the injector to combustion chamber copper seal IF the engine is running normally (no black smoke, no rough idle). Were that seal leaking you would get combustion gases, not raw fuel. vic

surlyoldbill
09-08-2013, 07:50 PM
I guess that Mike has already tried tightening the two high pressure joints shown?

MikeHowe
09-11-2013, 07:37 AM
I've done all the testing I can do now in order to find the leak, and haven't turned up the cause. Things I have found for a fact are...

1. The leaking fuel only appears around the base of the #4 injector once the engine has reached normal operating temperature.
2. The leaking fuel does not appear when the engine is merely idling, only once it has been driven
3. The fuel is not leaking from any of the hoses, nozzles, pipes, clips etc
4. The fuel is not leaking from anywhere on the visible portion of the injector.
5. There are no exhaust gases or chuffing from the injector indicating a problem with the copper washer seal at the injector base. Clean fuel is appearing, not black gunk.

Next step...remove the injector and have it tested for pinhole(s) or cracks or any other potential faults.

I'm told that cracks or holes in the injector body itself is quite a rare thing. Has anyone ever come across this happening? Mike

NORTON
09-11-2013, 09:31 AM
Looking at the 02 parts manual it shows a washer between the Adaptor and the Injector body.The Fuel Injector Supply Tube screws onto this Adaptor. I would assume that it is a copper washer because of the injection pressures, It would be worthwhile removing it and inspecting it closely for fractures. I realise that all the testing for leaks would possibly rule this out, but it might be done without removing the injector.

Boater
09-11-2013, 11:42 AM
It sounds to me like maybe the nozzle is not screwed properly onto the bottom of the injector, that joint will be down the tube but above the copper seal with the head.

Having read up on injectors a bit when I was having trouble, I would not mess with this myself, some of the internal parts are very small and difficult to see. I would remove that injector and send it to a specialist to test and repair if necessary.
My thinking there is that if the nozzle is not screwed fully home could internal parts move out of place and then get trapped int he wrong place if you just tighten it up? I don't know!
In theory any Bosch approved service centre (for diesel fuel systems) should be OK (you can find a list on Bosch UK website).
There may be some non-approved specialists worth looking at too, I bought a new injector from United Diesel (http://www.uniteddiesel.co.uk/about-united-diesel.php) and their man Keith certainly seemed to know about injectors. I'm sure they had videos of one of their test rigs on the webste before but I can't find it right now.
Of course it won't hurt to phone a few and talk the problem over with them, they may have come across something similar before, having more experience of diesel injectors than a local garage - they might even say it's fine just to nip it up yourself!

MikeHowe
09-11-2013, 03:42 PM
Thanks for the advice chaps. Because I'm inexperienced I'm going to get my mechanic to remove the offending injector and we'll send it off to an injector specialist testing and repair place. I suppose that if they find the fault, then at least I will know what the cause is but will be faced with a repair/replacement bill. If they don't find a fault, I'll avoid the repair bill but I'll be none the wiser as to what is causing the leak. I'd be very surprised if the injector is not the culprit.

Earlier this year it was pulled, with a struggle, from a damaged head after a serious black death case which had been undetected for a long time (if only I knew then what I know now!). Perhaps it was damaged during the struggle. :idunno:

It will be away for a week apparently, so I'll let you know the results just in case this ever happens to anyone else.

(If someone finds the leak in a more obvious place I'll feel like a right prat and will have to dream up an elaborate cover up :smirk:)

surlyoldbill
09-11-2013, 04:11 PM
It wouldn't hurt to just buy a new injector and have the old one around as a spare.

Texadelphia2006
09-12-2013, 01:03 AM
Mike,

My Aun't's 06 (RoadWrek(trek) had a similar problem after the idots at Hagerstown Freightliner replaced the injectors and supply lines......the wells would fill with clean fuel.

After a few attempts to locate the leak - I removed the cover and used some towels to soak up the fuel in the wells and used brake cleaner to make sure that the wells were absolutley clean, dry & free of any residue (after the engine cooled off from her drive from Philly to Texas).

Then after a brief start, idle and drive (had to do this more than once to be sure of where the dribble was coming from, as it wasn't a huge leak) - the source of the leak surfaced using a flash light and mirror - the supply lines to two injectors were not tight, and one was not quite centered - three out of five would dribble fuel. Number two had a more noticeable leak. Using a line wrench I was able to loosen, check and re-attach the lines, and dry out the area to drive and test again.
No leaks! But I did notice the idiots at the above mentioned dealer removed the drain pipe from the rear of the head and didn't bother to re-install it.

The leak was not very noticeable at first - I thought the wetness was from residue I had missed at first, but after watching (patiently) you could see the fuel well up very slowly around the supply hardline.
No leaks......:cheers:

surlyoldbill
09-12-2013, 01:54 AM
Tex, I think Mike's leak was on an injector that WASN'T worked on, but that doesn't mean that they didn't remove all the fuel lines to work the bad one.

Good tip.

MikeHowe
09-12-2013, 08:22 AM
Thanks guys, but if you look at the testing I've done at the bottom of page 1 on this thread (which I've since repeated on every conceivable bit of hardware in that area) I can conclusively say that none of the fixtures and fittings are leaking. Which leaves the injector itself, hence it's going off for testing.

I suppose I could just buy and install a new one, but maybe this one is repairable. I'll take advice from the injector specialists on that. Thanks for your input, it's much appreciated.

MikeHowe
09-30-2013, 08:37 PM
It sounds to me like maybe the nozzle is not screwed properly onto the bottom of the injector, that joint will be down the tube but above the copper seal with the head.

Having read up on injectors a bit when I was having trouble, I would not mess with this myself, some of the internal parts are very small and difficult to see. I would remove that injector and send it to a specialist to test and repair if necessary.


I just wanted to update those of you who have been really helpful to me during this episode with the conclusion (hopefully) to the story...

I did as suggested by Boater (and others) above, had the mechanic remove the injector and send it off to a specialist for testing. The injector failed the pressure test but the specialist was able to repair it and send it back. Although I don't know the exact details of the fault they reported that the failure could indeed have lead to fuel leaking out and welling up into the injector valley, which is indeed what I had concluded was happening after doing all my experiments (see pages 1 and 2 on this thread).

The repaired injector looked absolutely gleaming and like new. We popped it back in, took the van for a test drive, no leaking fuel - hooray.

So it would appear that this was a relatively rare (so I understand) case of an injector leaking from the joint, possibly at the nozzle. If I can get more detail from the specialist about the exact nature of the fault I'll let you know.

And for good measure, on my way to the garage to get the faulty injector out the chirping I'd been hearing at start up and shut down manifested itself into a seized alternator 'clutch', which is being replaced tomorrow. Jdcaples did a nice thread on this issue for those that may want to learn more - http://sprinter-source.com/forum/showthread.php?t=10187&highlight=belt+chirping

Boater
10-01-2013, 12:08 AM
I'm glad you found the problem in the end, it was a real puzzle!