I've certainly heard of other cars having similiar problems
after being run cold for only a very short time.  The ECU seems
to get confused about appropriate mixture during the next
start.

I suspect your "flooding" diagnosis is correct.  The old
technique from the carby days works on most newer cars: when it
does this, hold the gas pedal flat to the floor until it starts
(it shouldn't take long).  If you've already tried that and it
didn't work, we'll need to think again.

John

Jim,

This seems to be a fairly common problems with Sentras of that
vintage.

We have a 99 Sentra and, no matter what the outside temperature,
(we've had it happen in the winter as well as summer), it's had
problems turning over after it's sat for more than a couple of weeks
without being run.

This is what I've discovered,

1.  My local technician said that this most likely is caused by one or
more leaky fuel injectors.  This isn't a problem if the car is started
regularly, but if the car is left to sit, the injector(s), slowly leak
fuel into the cylinder heads and, basically, floods the top of the
piston head with fuel.  

Liquid fuel doesn't burn.  Thus the starting problems.

2.  When this happens, there's the "easy" way to get the car running,
and the "hard" way.

The easy way is to completely floor the gas pedal and do NOT let up
while cranking the starter.  You may have to run the starter as long
as 15 or 20 seconds (or longer) before the car will crank over, but
basically, what you're doing is burning/forcing the excess fuel out of
the cylinders.  The car *will* eventually crank over.  

The "hard" way is to remove the spark plugs and let the car sit while
the pistons vent the excess fuel out of the plug holes. This can take
as much as an hour to make any difference.

Of course, the *best* way to correct this problem is to fix the leaky
injector(s) and the problem will go away.  However according to my
technician, if the injector is only leaking enough to affect the car
only after several weeks, it's probably not worth the cost to repair
it.  He did caution though that if I don't drive the car often, it's
better to have it repaired because there's always the possibility that
the fuel could leak down the cylinder walls and if the rings are worn
enough,, there's the possibility that some fuel could get into the
lubrication system.  

And of course, that's never a good thing.  :-)

Anyways, I've found that as long as I start the car at least once
every two weeks, I've never had a repeat of the hard start problem.

Dang, that reminds me, I *have* to get around to putting a for sale
sign up on that car. *sigh*

As always, YMMV..etc etc.

cheers

This condition is due it Nissans infinite wisdom and forward thinking... NOT

For some unknown reason , Nissan Decided to only use 2 rings on each piston
instead of 3 like most engines do.

99% of most engines use 3 rings, a compression ring, a scraper ring and an
oil ring.

Nissan only used 2 rings on the GA series engines used from 95-99 , therein
lies the problem.

With only 2 rings per piston/cylinder it becomes quite easy to flood the
engine due to "lack of proper compression"
at start up, hence the flooding.

this is a VERY common complaint. learn the flooded engine start up method
and all will be ok