Club 80-90 Forums

Hey experts, I've trawled through most of this and other sites for clues as to how the LDA device works on a JX engine. I first took notice of it when I saw a fuel leak from around the pivot, and have fixed this with a new seal from the Brickwerks posse. I'm a bit mystified as to how the whole LDA bit works though. From what I understand, a pipe from the intake manifold transmits air pressure to the diaphragm end of the LDA. This pressure increases, I guess, as the turbo spins up. The diaphragm then moves the rod, turning the pivot and thus increases the fuelling when the turbo gets going. Is this roughly right?
Trouble with my LDA, it don't move at all, no matter how high I rev the engine. If I take the pipe off the LDA, I can feel air being forced out of it as I rev the engine, and if I connect a spare bit of pipe to the LDA and blow into it (bloody hard!), I can get the LDA rod to move about half of it's travel. It doesn't move with the pipe back on to the intake manifold though.
So am I looking at a tired LDA here, and does it make much difference to the performance anyway??

Any advice much appreciated, and I've hopefully attached a picture of the offending bit.

Cheers, Puzzled of Hants.

it only moves when the engine is powering the van along! the lda puts more fuel into the engine.try disconnecting the pressure pipe and drive the van [plug the end of the pipe] to feel the difference in performance.
good luck.

^ What he said

It only moves while the turbo is actually producing pressure (which it doesn't while stationary) ..the more pressure, the more movement.
While you're experimenting with the pipe ...take it off ...pull the LDA rod all the way out ...block the pipe inlet with your finger and let go the rod ...if it moves all the way back, the membrane is shot and you need a new one.

Hey, thanks for the advice and explanations. I tried disconnecting and plugging the pipe, and I'm pretty sure the performance degraded a bit.
I also tried the bit about pulling the rod all the way out and letting go. I'd blocked the inlet bit, but the rod moved straight back. It was clearly under some quite heavy return spring pressure. I'm guessing the spring in in the can with the diaphragm, as none is visible anywhere on the rod and linkage.

Cheers, Geoff