Petrol engines 1.9 Timing
Technique applies to DJ or DH
DG Vs DJ (comparative advance curves)
HarryMann: 1.9 DH Ignition timing (DG with Digijet fuel-injection)
Before getting all this checked/reset - you should really quickly physically inspect that the vac/adv. and cent. unit 'seem' to be working OK, e.g. no obvious leaks in hoses, blockages at pressure tappings, and no gummed up dizzy. Because unless someone has been swinging that dizzy around lately, that's not what's wrong - it'll be the vac or cent. unit, so don't go swinging it around unless you know for sure it needs swinging! It might stop the popping back but lead to over-advance under load at speed if the dizzy's a mess.
NB. Always ensure the distributor and its adjacent housing have clear and accurate marks of their physical position, before loosening or swinging the dizzy. This can be accomplished using a sharp centre punch to put a couple of spot marks directly next to each other, allowing an accurate return of the original static positioning and to see physically at a glance how much any changes have moved it.
Here goes: timing a DH
Static timing 5 degrees ATDC +/- 1 degree (also at 900 rpm with vac hoses disconnected and ISU plugs disconnected from unit and plugged into each other) That's After TDC, which may seem strange but is a consequence of the Vacuum Advance/Retard unit's operation, so...
You really must not trust a static setting, it needs strobe timing, so that can actually see the true advance working and check it at 3 conditions at least:-
Normal Idle 850 rpm +/- 50, test idle 900 rpm Idle Stab. Control unit (on L/H engine flitch panel, near coil and Hall control unit) MUST have its plugs disconnected and joined together first.. Pull both hoses off vac/adv unit on dizzy
Firing order 1 - 4 - 3 - 2 Number one is the front right cylinder. When viewed from the rear
Set engine to 900 rpm, note down the advance angle... (against TDC mark). The following figures are relative to that figure, that is, in addition to the figure noted (which should be about 5 ATDC), so being After TDC you need to ADD that to the figures you see. (Subtract if its BTDC, true advance)
Cent. adv starts at: 1050~1150 rpm @ 2400 rpm should be 16~20 deg. @ 3800 rpm should be 21~25 deg. and not increase thereafter.
So if you find its 5 deg ATDC at 900 rpm, you'll be looking for about 13 deg. and 18 deg. at 2400 and 3800 rpm respectively. And the the strobe mark doesn't start moving until above about 1100 rpm
If you find the static setting is out much, reset this first, provided you have followed the pre-test instructions properly
Vacuum advance/retard You can't test this accurately without a manifold vacuum gauge, and again you need to be thorough and not confused about the process - have a clear understanding of what your are doing and why. But you can at least quickly pop the pipes back on the vacuum unit one at a time to see that the timing does move i.e. the vac unit appears to work and hasn't got a broken diaphragm, or isn't 'stuck'.
Here are the figures if you need to get a garage mechanic to check/set it for you..
Same as before, except with vac unit's pipes conencted back up; ISU unit's two plugs connected together; idle at ~900 rpm and note down the basic timing setting first (so you can Add or Subtract it, depending on if its ATDC or BTDC respectively) then...
Vac Advance starts 190~230 mbar(14~17 cm Hg) Ends @ 360 mbar (27 cm Hg) with 12~16 degress advance
Vac Retard starts 100~220 mbar (7.5~16.5 cm Hg) Ends @ 260~360 mbar (19.5~27 cm Hg) with 9~11 degrees retard
