Club 80-90 Forums

Hello! First post here..! Hope not a stupid question..
I have an '89 Caravelle with JX engine. Today I was checking the LDA valve and it seems to not work properly..
It's not the one with the membrane.. It's all metal with some kind of "piston " inside. If I connect a bike pump instead of the pipe from the turbo the rod moves but it immediatly loses pressure and goes back to resting position.
I can ear pressure to be relieved at the interface between the valve and the bracket to which is connected with 3 screws..
I tried to manually put the actuator in the "boost" position and it seems to rev more.
Since the LDA is all metal and without membrane any advice for further checking? How should it work??
Any advice appeciated!!!






 

It operates on vacuum not positive pressure, what happens when you apply a vacuum

Didn't try since I read it works on positive pressure coming from the turbo..
And since there's a spring inside with vacuum it can't move "back" any further!

alebassa wrote: ↑26 Aug 2024, 18:31 Didn't try since I read it works on positive pressure coming from the turbo..
And since there's a spring inside with vacuum it can't move "back" any further!

I may have got it the wrong way around now I think about it


The LDA only gives additional fuel to match the boost so manually operating it will give more power , try taking it for a drive with a helper and operate the LDA though they will move I the engine is revved , is it a rebuildable one ?

A little confusion here?

The LDA in your picture looks just like mine, I think, probably a replacement rather than having the patina (grime) of the original.

It works off a positive air pressure, but not from the turbo. The connection is to a little spigot on the inlet manifold.

viewtopic.php?p=8014631#p8014631

The pipe should connect this to the rear connection on your LDA, in your pic pointing down at 4oclock. Your LDA does have (or should) a diaphragm, secured in the folded joint 1/3 of the way down the canister. Positive air pressure from the inlet manifold (which will increase as the turbo spins up) will act on the diaphragm,moving the rod and increasing the fuelling.

Testing the LDA. Blow on the pipe? And burst a blood vessel. Easy way is to pull out the rod (mimicking positive air pressure) and put a finger over the pipe. Rod retracts = holed diaphragm. Rod stays still = deep joy.

RogerT wrote:Easy way is to pull out the rod (mimicking positive air pressure) and put a finger over the pipe. Rod retracts = holed diaphragm. Rod stays still = deep joy.

That’s my understanding of the easiest way to test them. If required, new diaphragms can be bought and fitted - you need to cut the can open along the folded seam and then bolt the two halves shut again with the new diaphragm in between. Alternatively, new LDA’s can be sourced from www.dieselkontor.de - they’re the owners of the only machine that makes these items so all other stockists must buy from them. Be aware that they make three different versions of the JX LDA which have different strength return springs, and suit different types of vans.

I would not get a new LDA for the sake of a rubber diaphragm. As above.
Bosch pn 1 460 503 304 fits. Make sure the washers under spring are correct -
no tension on diaphram when you put it together or it will split in no
time. I have the instructions - in German if you need. Easy to
translate with google etc

covered alot on this great forum

Thanks all for your replies!
I've ordered the new rubber and will go on with the rebuild of the valve!!

I have ordered a new membrane..
However it seems to be a little different from the original, since with the original the piston can go completely inside without effort, while with the new one I have to push it inside.
Is this normal?? Or did I buy the wrong membrane??



top one is the original, bottom the new one


new membrane in...


I have to push and deform it to make it go in..