Lantra (Elantra) 1.6 occasionally won't start from cold

I have a 99 Lantra 1.6 which very occassionally won't start from cold;
just goes on cranking eventually flooding the engine with petrol. The
only solution is to leave it for about half an hour or even until the
next day and try again. I would say its only 1 in a hundred times but
can be very inconvenient if its an important journey ! I met someone
else recently who has the exact same problem on his Lantra 1.6 so it
must be some common ailment.
I also notice that often when starting, the engine does not catch
until the point where I release the key from the starting position and
it then starts from its own momentum; like its not getting enough
electricity to fire with the engine turning over under the starter
motor. Compare this with my sister's Rover metro which fires up at the
slightest touch of the starter.
I have run an extra earth cable from the battery straight to the
cylinder head which seemed to help but I have still had the problem
since then.
Once started it runs fine and has not been a problem when starting
from hot.
Is there any particular relay or connections that I should clean to
help get more juice to the coil or any other reason for this problem?

 

May be you have to wait 2 seconds to let the fuel pump go into pressure; you
can notice this more when the tank is almost empty.

 

Possible coolant temperature sensor problem?

(Just a guess-- don't replace without verification)

 

Its not waiting for the fuel pump to prime Zotto; in fact I had the
problem again today and as it was flooded with petrol, I left it 5
minutes and then started without waiting for the pump; it ran.
Probably not the temperature sensor as when it does start, it runs
fine; if it were the temperature sensor, I would expect it to run
rough for a while?
I'm sure the spark is just not powerful enough when cranking but don't
know how to get a more powerful spark. Maybe the new ignition leads
are rubbish as I didn't have the problem with the old leads ( I
changed them because the insulation had gone on one lead due to oil
rotting it); anyway to check these?

 

Have you the right spark plugs? If there is a leakage in leads you could see
in total dark some little sparks somewhere around them.

 

I think I found the problem. The new HT leads have double the
resistance of the old ones e.g. the new longest HT lead is 7K ohms
whereas the old one was 3.2K ohms. I also noticed that the spark plugs
are the resistive type. Take all this resistance plus the voltage drop
on the systen due to cranking the engine and hey, no spark at all ! I
changed the leads for copper cored (self made) and now the car starts
while cranking instead of just firing as I turn of the key !
Brilliant. Resistive HT leads are such a pain; always cause trouble. I
think the manufacturer goes all out to reduce emf emissions which
works very well if I can't even start my car !
Here is how I made the copper cored HT leads. The problem is of
course the fittings for the coil pack and spark plugs which cannot be
bought. To get around this, use the fittings from the resistive HT
leads. Chop the cable off right next to each fitting. Screw in a self-
tapping screw (I used a 1 inch one) half way; then saw off the head of
the screw; file or grind the end to a point and screw on the copper
cored HT lead ( you can buy this from car accessory shop). When both
ends have been assembled, I mixed up some araldite and applied around
the join to seal it and strengthen it. I'm not sure araldite is the
best stuff to use as it can crack up in cold weather. Maybe some
silicon sealer would have been better.
I have noticed no interference on the car radio; although the leads
are now copper cored, the plug caps and the plugs themselves are
resistive so this helps with supression.