|Timing the TDI|
This applies to 2.5 TDI models, 88, 102 and 151 hp models 1996 - 2003.
This is not a how to, this is not a blow by blow account, just a page of notes on some pitfalls that you are likely to encounter.
Chances are your garage will do this work for you, after reading this you should have a pretty good idea of what is involved and what to quiz your garage about to gain confidence in them, and, more to the point for you, the owner/driver to feel like you know whats involved so it feels like your getting your monies worth when you get your bill!
The engine is TDI, Turbo Direct Injection. This IS NOT for 2.4D
To achieve lower exhaust emissions, good economy and good power output these engines are completely computer controlled.
The electronic governor is an output of the ECU (Engine Control Unit, basically a computer) and it's output is determined from several inputs into the ECU including throttle position, air flow into the engine, engine temp, ambient air temp, boost pressure and temp etc...
Obviously, this precise computer control requires an above average level of service when it comes to cam belt change or pump replacement.
The service interval for the cam belt (timing belt) is 80 000 miles. Although it is prudent to change them early as if they do fail chances are it will destroy the top end of the engine and you risk piston damage.
When replacing the timing belt it is recommended that you change both timing belts (the injection pump has it's own drive belt, separate to the main cam belt) all the tensioners, the idler pulleys, the water pump and the crank shaft pulley bolt as well as the rocker cover gasket.
That lot above will set you back around £200 from a VW main dealer.
The timing belt.
As per just about every other VW Diesel, the cam pulley is wedge mated, it is infinitely adjustable.
Okay, there are a few ways of setting this up.
On the pump pulley, should be a mark that corresponds with a mark on the pump body, or bracket, thats number one, make sure it is.
Fit your belt, tensioner and idlers.
Nip up the cam sprocket.
**Never, ever turn the engine with the belt connected with the wedge/plate removed from the pump, you will break very expensive... er... things)**
You should be somewhere near now, and it will probably run but...
The injection pump needs to be set into such a position so that one of the actuators in the injection pump has enough leeway to adjust the timing backwards and forwards to achieve economy, smooth running, low emissions and power. This means a "basic setting" has to be carried out.
The old school way.
If you have messed around with VW Diesels before chances are that you will be familiar with a DTI (Dial Test Indicator)
You fit the DTI to the back of the injection pump through the timing port via a threaded adaptor that fits between the injector pipes in the pump head.
If the measurement in more than .55mm the timing is too far advanced.
If the measurement is less than .55mm the timing is retarded.
To adjust the timing you do the following.
Once you are happy that the basic position is set, make sure all pulleys are tight, and the pump lock set to unlocked.
Now this works, to a degree, this figure [.55mm] was set on a new engine, but using this method I have found that the pump has had to be set as far as .7mm lift @TDC to achieve what I am meant to when diagnostic equipment is used.
A few ways of checking with diagnostic equipment.
VagCom timing checker.
If you have VagCom, there is a plug in (supplied with latest versions of the software)
Just reading off what VagCom says.
You will now get a list of numbers, in the second box should be 55, or there abouts, thats your pump timing.
If it's not, over 55 is advanced, below 55 is retarded.
Now, I need to check these parameters but, from what I have read..
If the actual timing is between .5° and 2° and the duty cycle on or below 10%, everything is cool.
I will update this method when I can find out a bit more about it.
Adjusting the timing.
It's properly hard to get it bang on, it takes a fine hand and a bit of practise, again, make adjustments by tiny movements on the cam pulley for the injection pump.
You can either undo the bolt and move the pulley in relation to the cam to get it near or use the idler pulley and the tensioner pulley for smaller adjustments.
Link to VagCom from Ross Tech
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