Mk3 Astra very difficult to start after 5 days parked

Hi,

I still have my mk3 1.4L 1992 Astra (CPI) with 236K miles and
counting. Lately, if it remains parked for more than 5 or 6 days, it's
almost impossible to start. Fuel pump can be heard priming and engine
cranks fine, but no life. I usually have to jump-lead the battery and
crank intermittently for 20mins, occasionally depressing the
accelerator pedal to the floor. Then it 'comes to life’ in a matter of
seconds and immediately idles smoothly with no sputtering or
vibration, as if nothing was ever wrong. This behaviour began around a
year ago and seems to be getting a little worse. Prior to this, it
could be parked for several weeks (two months once) and still start
first time. Mechanic cannot fine anything wrong. Travel for work means
that I'm not always around to start it once a day, which would avoid
the inconvenience but only mask the problem.

- Replaced faulty O2 and MAP sensors two years ago - back to 49mpg
fuel economy
- Had to replace starter motor because of this starting problem over a
year ago
- Plugs relatively new
- Recently cleaned the automatic choke (might it be gunky inside?)
- There are no error codes
- I'm thinking that since it idles and drives perfectly once started,
the electrics cannot be at fault (cleaned rotor arm etc. just in
case).
- I have eliminated weather as a factor - it could be warm and dry or
cold and wet - same behaviour - after 4 days parked in constant sub-
zero temperatures last winter, it started fine when it was -4 deg C.

I'd be grateful for any ideas please.

Thanks,
John.

 

For reference, I eventually isolated this problem: - I ran the engine
in the dark and observed plasma glow from two areas on the HT lead
connecting the coil to the distributor cap. I removed the lead and
stored it indoors for a week, re-connected it, and the car started
fine. The problem was resolved by replacing the lead, so my assumption
of electrics not being at fault was obviously incorrect. All I can
conclude is that the HT lead insulation was gradually absorbing
moisture from the air over several days and that the engine would
eventually start as the moisture slowly evaporated from the affected
areas due to arcing under the coil's HT during repeated cranking. The
car would start perfectly within two or three days because moisture in
air could not sufficiently penetrate the insulation over this period
to cause problems.