405 SRDT Fuel Leak

[Guy Ellingham]

Hi,
I have a 1996 405 SRDT. It has a D8A 1.9 turbo diesel engine. About a week ago I noticed diesel puddles under the engine block. After some time spent in the weekend looking for a leak I discovered the diesel is coming from a small rubber nipple-like pipe on the top part of the fuel delivery assembly attached to the front of the block (home handyman - sorry). When the engine is running this produces about a drop a second - not too good for the fuel consumption!

After reading the Haynes manual, taking off the intercooler, tracing the fuel lines, reading the Haynes manual some more and reading CitroJim's excellent post on replacing injector pump seals (boy that looks ugly) I'm thinking this is the fuel supply pump. Is that right? I can't find out anything about it anywhere but it has a fuel line coming in from the fuel filter and another line out which is presumably the return to the fuel tank. So is this nipple thingy some kind of relief valve? Does that mean a blockage or failure somewhere inside the unit? It has just started to get cold here (NZ) after a very mild autumn so it's the season for O-ring and seal failures.

I've tried attaching a picture to this post but a message says "The board attachment quota has been reached" so I've put it in the public space of my Microsoft OneDrive account instead - https://onedrive.live.com/redir?resid=B ... AD27%21107
The injector pump has 445-3 stamped on it so I'm pretty sure this is a Bosch unit especially seeing as the car is a 1996 model which I think was the last of the 405s. It seems very similar to the unit in CitroJim's post.

All advice and help welcomed. Thanks.

Cheers,
Guy

[Peter.N.]

Hi Guy

Welcome to the forum. The item you describe is I think the injection pump, it will have 4 pipes coming from the right hand end going to the fuel injectors on the cylinder head. I am no quite clear on where your leak is though, is it from a pipe or the pump itself, yours will likely have a Bosch pump which rarely give problems. Its often difficult to locate the source of the leak as the fuel is more or less clear and doesn't always come from where you think it does, clean it off and watch carefully and let us know.

Nice car the 405, I like them a lot, I have a 406.

Peter

Just looked at you picture, not quite sure what the plastic bit is, looks like an actuator of some sort but its not part of the pump, just fitted to it as far as I can see, is the fuel actually coming from the pipe?

[Guy Ellingham]

Hi Peter, The part I'm describing is on the top of the injector pump unit. It's a rubber spigot nipple thing about a centimetre long. It just pops off revealing a hole in the body of what I think is the low pressure part of the diesel supply. The diesel "leaks" out of this hole. It's part of the original build and I see it in the pictures of CitroJim's post about injector pump seal replacement. My guess is that it's the outlet of a relief valve inside the unit.
Cheers, Guy

[Peter.N.]

Never come across one of those and I have been running XUDs pretty well since they came out. Jim is probably the one to tell you, he is an expert on diesel pumps.

Peter

[Guy Ellingham]

Hi, I've added two more photos to show what I'm referring to. It's not clear from the pictures but this is the top end of the injector pump unit. The rubber spigot thing just pulls off revealing the source of the dripping diesel. See https://onedrive.live.com/redir?resid=B ... AD27%21107. Cheers, Guy

[Xaccers]

Never come across one of those and I have been running XUDs pretty well since they came out. Jim is probably the one to tell you, he is an expert on diesel pumps.

Peter

Might be something only on the TD Bosch pumps then as all mine have it.
As to what it's for, or why it could be leaking, I'm sorry I haven't a clue.
Had a look through Jim's pump strip down and it's part of the head so he doesn't go into it. Can't remember it coming up in any of our conversations either.
Looking at a cutaway diagram of the pump it does look like an overflow for diesel that has got in under the on boost diaphram.

[Oldpug]

That`s the Bosch injection pump only used on 405/306 with an inter cooler .
Its difficult to be sure from the images but I think there should be a small leak off pipe which pushes on ?? and has fallen off??
The large unit at the top is a diaphragm with a vacuum pipe that goes to the inter cooler.When the throttle is floored the diaphragm opens a valve to supply more fuel.So there must be something for excess fuel??
Remove the inter cooler and have a close look and follow all the injector leak off pipes and any other ones the same size,I think you will find there are various pipes all over the place on these models.?? You may find a pipe just dangling?? Its a long time since I`ve worked on one of these.

[Xaccers]

That`s the Bosch injection pump only used on 405/306 with an inter cooler .
Its difficult to be sure from the images but I think there should be a small leak off pipe which pushes on ?? and has fallen off??
The large unit at the top is a diaphragm with a vacuum pipe that goes to the inter cooler.When the throttle is floored the diaphragm opens a valve to supply more fuel.So there must be something for excess fuel??
Remove the inter cooler and have a close look and follow all the injector leak off pipes and any other ones the same size,I think you will find there are various pipes all over the place on these models.?? You may find a pipe just dangling?? Its a long time since I`ve worked on one of these.

Nope, its just a rubber cap with a short spout on it.

[Guy Ellingham]

Thanks for your help guys.
Yes, it is just a rubber cap with a spout. I'm pretty sure there are no disconnected leak-off hoses that attach to it. In the middle of the bolt-like thing it attaches to, is a small hole that leaks the diesel (just visible in the photo).
What you are saying about the top of the injector pump unit housing a vacuum diaphragm that operates a mechanism (needle?) to provide more fuel for the turbo boost makes good sense. XAC, you mentioned a cutaway diagram of the pump - can you post this somehow so we can have a look at it please. I've searched the internet for details of this Bosch unit but haven't found anything yet.
I'm thinking the diaphragm assembly is going to have to come apart to get to the bottom of the problem. I've been reluctant to do leap in before understanding what's under there in case I damage a difficult to obtain part or liberate some small bits that sproing into the bowels of the engine bay.

[Xaccers]

I'll find the page that had a great image and post a link as soon as I can. Its on a 306 tuning website.

[Guy Ellingham]

Hi, I found an excellent document on the Bosch VE injector pumps used in the 405s, and probably quite a few other models as well. See Bosch_VE_Pumps.pdf in my Onedrive space - https://onedrive.live.com/redir?resid=B ... AD27%21107. It explains the construction and workings of these pumps really well including the add-ons for various engine types such as the "Manifold Pressure Compensator" unit added for engines like mine with turbos! It would probably be a handy resource for all forum members if someone could grab it and post it here in the appropriate place.

Pages 38-40 are the relevant ones for a description of the part of the injector pump unit we have been discussing with respect to my leak. After some comparison of the diagram with the unit in my car, I think the diesel is dripping out from what is labelled "15. Vent Bore". I guess this exists so that when the diaphragm is depressed by pressure from the turbocharger, air under the diaphragm can escape the lower enclosure then be drawn back in as the diaphragm returns to its neutral position. I can't see why diesel would normally be under the diaphragm so I'm guessing there is some kind of internal leak possibly up the "guide pin", "sliding pin", "control cone" route. I'm only guessing though. Unfortunately the schematic doesn't show the seals or O-rings that are probably in there, and probably failed. Hmmm.

[Xaccers]

Here's the page I found with the image
http://www.pug306.net/index.php?pageid=boschtuning" onclick="window.open(this.href);return false;

It mentions damaging the guide pin seal, which I guess is just a tight fit seal so could wear from age and let diesel through perhaps?

That's an excellent document you've found

[Guy Ellingham]

Thanks for the link to 306 article. It's very interesting and adds quite a bit more to understanding the mechanism especially the cone mods. The "Manifold Pressure Compensator" add-on for turbos I mentioned earlier is of course more commonly known as the "LDA". I think it stands for something unpronounceable in German but anyway, a Google search for "Bosch LDA shaft seal" produces a lot of interesting results. I haven't found anything specific to my unit yet so I still don't know quite what's in store with the repair. Will let you know as I find out more. Cheers, Guy