Timing Alterations

[ian2000t]

I want to start playing with my timing a bit (reasons below) - currently has Monark Nozzles @ 163 bar, and is running 0.98mm.

What is the easiest way of regularly changing the timing? I wish it was as easy as a petrol distributor - slacken one nut and spin dizzy while engine running with a strobe light connected.

It also seems the last time I set the timing with the gauge it was VERY sensitive - to the point that tightening the sprocket up could move it slightly and give a completely different number.


Reason's for "playing"

At low revs (1000-2000ish) and light throttle it really clatters (possibly too advanced), although above that, and under heavier throttle it goes quieter. I read something suggesting a low compression diesel could clatter more due to less-complete burn. Maybe time for a comp check?

Also, at motorway speeds (2500-3000rpm) it there is a lot of knocking - it's done it ever since I've had the engine (even with the old nozzles pre-calibration) so I'd assumed it was vacuum pump as it sounds almost like one one knock per revolution. However, recently trip has highlighted that with autobox in lockup, taking foot off the throttle (revs don't change) it goes away completely - making me think it is definitely injector/pump/fuel related - not vacuum pump, which would function the same regardless of throttle.

I wanted to play around with the timing to see if either of these clatters gets less/louder.

Another strange thing, is normally mine feels quite sluggish to come on boost, but randomly sometimes it will feel really quick and will boost much easier and sooner. It's a completely different car to drive on those days - but when it happens it's only like it for a day or 2 then back to it's usual self. I CANNOT understand this at all - I thought it was different "blends" of fuel, but in the winter I was running straight diesel lots, and the same happened a couple of times during one single tank of "just diesel".

I have read that too much advance will cause slower spool because of less heat, so I also want to see if retarding it slightly makes it feel like one of it's "good days".

I also only get 27mpg round town, and 31mpg on a recent 500 mile trip (although fully loaded at 80mph). These are UK gallons/MPGs! These don't alter between diesel/wvo etc. I want to see if this changes.

[745 TurboGreasel]

How old is the pump, and does it leak at all?

To easily affect a change, draw a witness mark on the pump and bracket. loosen the 3 bolts, and turn the pump do displace that about 1mm, tighten up, and go for a drive.

Could your cold start advance have been stuck when you set the timing? does it work?
Does the altitude compensator stay consistently plugged in?
Boost have you measured it?what is the difference between good and bad?
tried any super slippy diesel clean products?

[ian2000t]

Pump is old and does have leaks (top spindle and between the main pump and the head). Cam leaky seals affect timing?

Cold start works fine, didn't when I bought the car but I replaced it with a new waxstat.

Don't think my UK pump has the altitude compensator.

Boost gauge still reads the same - 16 Psi (MBC) it just seems to build boost sooner and with less throttle.

[745 TurboGreasel]

You might well be sucking air under load at the filter, or drive shaft seal.

alt comp = 2nd blue wire, goes to side of pump

If the cold start was not disconnected when you set the timing, it's wrong.

Also inspect for any loose/leaking boost tubes.

Measuring transfer pressure (controls dynamic advance) is a good idea on an old pump, but you need a modified out bolt, or modify a VW out bolt spacer for a 100PSI~ish gauge

[ian2000t]

Cold start definitely disconnected when I set timing last time.

No other wires around the pump. Pretty sure uk pumps don't have alt compensation.

Turbo does make a whine under boost (on top of the normal whistle) but all boost hoses replaced, inlet manifold resealed, and no sooty marks around turbo hot side. Whine doesn't seem any different on "good days".

What effect would sucking air have on timing?

Wouldn't know where to start measuring transfer pressure. Maybe it's time to start resealing my spare pump.

[745 TurboGreasel]

It wont advance as much under load, but you'll feel power loss from reduced fuel more.

maybe a long clear return line you can route above the hood to look for bubbles as you drive?

http://www.vwdieselparts.com/forum/viewtopic.php?t=5936