Club 80-90 Forums

1.6 JX TD Engine. Lacking power. Just changed diesel pump because old one leaking fuel. My old LDA was pretty well siezed aswell.

When the engine is revved, the LDA is not moving, there does not seem to be much / any pressure in the vaccum line feed to the LDA unit. The turbo is brand new. What could the problem be? Waste gate? If i uncouple the LDA to the pump and wedge open the linkage on the pump, i have plenty of power so i believe the turbo is functioning correctly.

Anyone any ideas??

You don`t get a lot of boost off the turbo until you`re under load, ie moving. If you ar`nt sure of what the turbo is doing then get a boost gauge rigged up temporarily into the cab area where you can see it when driving, you can tee off the pipe from the inlet manifold to the LDA.

Get the `van warmed up and then you need an open road where you can give the engine full throttle under load in third gear through the rev range, you`ll see the turbo start to boost from around 1800 rpm, and will peak out pretty quickly but will hold boost through to the red line, the amount of full boost depends on what the turbo place has set your wastgate to. Mine was rebuilt and was only doing 7 psi, VW manual states limits between 8 and 12 psi, so I`ve adjusted the blow-off system with a bleeder valve, now gets the full 12psi boost, with this extra boost and the fuel pump cranked up to make use of it, along with some other simple mods, it`s like a different `van, a lot quicker, goes up hills without dying, etc
Actually accelerated up the mountain last week at the Isle of Man do

If the LDA is knacked (it`s only a diaphragm in a can), then you won`t get the extra fueling when the turbo boosts, so it`ll feel flat and won`t accelerate. New LDA now obsolete from VW, but still available from German suppliers like Gunzl. (around £130)

Hi Westy,

The LDA is good. If I rev the engine hard, nothing happens to the LDA, my friends van moves when revved.

If i disconnect the LDA and open the cam, the van performs superb, in fact i wouldn't want for any more power.

What produces the vaccum feed? Is there something i can adjust??

It`s not vacuum, its pressure boost. That`s what the turbo is for. The thin pipe connectind the inlet manifold stub to the LDa is where the boost comes from, try pulling that pipe off and blowing through it, also test for air pressure from the inlet stub when you rev the motor, it could just be a blockage. If you have pressure from the pipe to the LDA and it still doesn`t work then the LDA is duff, it`s only a diaphragm in a tin-can, when the turbo produces boost the diaphragm moves under that pressure, pushing the actuation rod out and thus increasing the fuelling. Wedging the fueling arm open will do the same thing but will permanently be over-fueling the engine, which will increase the black smoke until the turbo boosts enough air to burn that extra fuel.

When you say the LDA is good, how have you tested it? If you can connect a foot pump or similar to the LDA inlet stub and pump air into it you should see if move if the diaphragm is OK. DON`T use an airline, it`s too much pressure unless you can regulate it to under 12 psi.

Hi Westy,

Been out putting up a trampoline for the kids, back on the van now, going to test the pipes.

I will check the LDA, but this is the second unit i've tried. I will check the pipe & stub for blockage.

Westy Club Joker wrote:You don`t get a lot of boost off the turbo until you`re under load, ie moving. If you ar`nt sure of what the turbo is doing then get a boost gauge rigged up temporarily into the cab area where you can see it when driving, you can tee off the pipe from the inlet manifold to the LDA.

Excellent advice

I have the same problem, but due to boost gauge T'eed into Manifold/LDA line, I know mine's boosting fine
However, my pump has an integral LDA, and have had to free it all up once, as the 'pin' had seized in the bore (very close tolerance). It isn't seized now so suspect the diaphragm or soemthing even deeper (Oo, 'er, top off pump -again- not for the feint hearted!)

As WCJ says, get a gauge, even a hashed up one on the line and see what boost you're getting, if much less than about 7psi on full throttle above 2,000, then wastegate is likely, you can do a quick and dirty check of turbine wheel play + wastegate action by removing the exhaust pipe (on the T2 Garret anyway, its easy, drop the activation rod off and look at the valve seat condition).

Check the adjuster isn't holding it open as well, people do fiddle and might have adjusted it for delayed opening - but the wrong way!

If short of boost then might also be the BOV on pulley end of inlet manifold, picture in Wiki.

Here are some Wiki links, but mainly the rarer Garrett T2

Setting up the wastegate

BOV - Last picture in this article

Just checked my pipes, revved engine and over 2000rpm got plenty of boost through the pipe. Tried to test the LDA, attached a footpump to the rubberpipe and nothing moved. No way will it move if i blow into it. How much should it take to make it operate??

Above about 5 psi should see it moving. They are known to be a problem with the JX pumps, the later AAZ type pumps and the Golf GTD use a totally different set-up.

If it does turn out to be knacked, then you can use the LDA and pump top off a Golf GTD type pump which has the more usual alloy bodied thing that you usually see in the AAZ pictures. You`re into fairly specialist knowledge to get it all sorted though unless you`re pretty handy, and you`ll have to cut the engine lid insualation for clearance, then rivit a flat plate to cover the hole.

New LDA available from German suppliers, or try for a second-hand JX pump or LDA if someone will split it

At a guess, it should start moving with just a couple of psi on it, depending on the spring loading and star wheel setting (if it has one)..

There are a few diff types of LDA, some have much more adjustment than others.

1) Are you sure the pin is free to move? Clean & lube with diesel fuel. Surfaces should be almost instrument quality!

2) Are you sure it is rotated to a position that gives a reasonably decent fuel-increase Vs boost rate? [you do know they can be rotated to 'tune' the slope of the pin's action?

3) Do the screws and locking nuts look like someones been messing with it, mostly, injection pump setting screws are paint-locked and shouldn't be mullered of course

4) If doesn't move (I can't see if my one does or doesn't) then, suspect the diaphragm, surely, or a leak in the lid, but it would have to more than pin-hole I'd have thought

If I find my 'LDA no-worky' problem, I'll post again and et you know... TBH, I'm a bit confused about mine, as I should know these well by now

LDA on the JX is a small tin-can affair lying on it`s side on a bracket above the fuel injection pump, with a diaphragm and rod. It`s nothing like the AAZ type alloy housing with the top cover and pin inside.

As with most /all rubber(?) diaphragm type actuators, they either work or they are knacked. It`s possible to covert to the more technically advanced LDA type from the tin-can type, but then again, anything is possible with time and money and know-how

LDA on the JX is a small tin-can affair lying on it`s side on a bracket above the fuel injection pump, with a diaphragm and rod.

Oh, one of dem fings, a bit of an afterthought by messrs VW

Then need to get one photographed up for the Wiki, as seems they are quite a common failure item from what you and others say