Ignition Timing Oddities (Was A100 fuel problems)

[Gary Brown]

My 1988 A100 (2.0 RT engine) has been off the road now
for almost 2 months as I struggle to suss out the
running problems. I've not given up yet though.

Background: Was running ok until it cut out once miles
from home. Now very difficult to start (battery
flattening type difficult). If I can start it, then it
will run ok for about 10-15 mins then cut out. I tried
driving it but can't get out the road without it
stalling!
I always get a spark. I have swapped the warm-up
valve, ISV & fuel distributor for known good ones but
no change. Cold start valve ok, idle switch ok, no
vacuum leaks found. Plenty of fuel getting to the fuel
distributor.

Not sure what to try next, but today I decided to play
with the ignition timing and see what it was set to.
Previous owner said it had been modified to use
regular unleaded. So I was surprised to see some sort
of tamper proof cover over the distributor clamp bolt
and it didn't look like the cover had been disturbed
previously.
Anyway, car wouldn't start, so I adjusted the
distributor to different positions and tried to start
the car each time. Eventually I got the car started,
and when warm I measured the timing by using a strobe
directed at the aperture on the bell housing . Haynes
manual doesn't make it clear whether the reading
should be taken in the middle of the aperture or the
lower edge, but the figures below are for the lower
edge.
Well the reading was about 24° BTDC, so I adjusted the
distributor to it's original position and this was 14°
BTDC. Switched off and tried to restart. No go. Put
back to 24° and it did start (although not
immediately). I then adjusted the distributor to 8°.
Switched off and tired to restart. No go. Put back to
24° and it started!
It was getting dark and wet so left it there.
I find this all rather strange as the standard should
be 18° and  I believe 8° is the correct setting for
the regular unleaded I was using.So why does it start
best on 24°? Maybe it's all a red herring and my
'fault' is just being partly compensated for by
advancing the timing?

Gary



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