"...also the engine runs very rich - is this common?..."

It's not uncommon for it to smell a little bit rich when you first start it cold, but it should lean out pretty well within a minute or two. Never should it run REAL rich.

Being that your's IS running very rich, I would thing you could ignore some of the common problems that LIMIT fuel delivery, like bad fuel pump(s), pump relay, radio interference relay, fuel filter, etc.

Look for the things that can cause an over-rich situation, like bad fuel pressure regulator, engine coolant temperature sensor out of range, cold start injector stuck open, obstructed return fuel line, bad air mass meter (on the Bosch LH systems), bad manifold pressure sensor (on Regina systems), ...those are a few of the biggies.

Also, reading out the fault codes may be a clue, but take them with a grain of salt. For instance, you might read a code that says the O2 sensor is out of range, but it might not be the sensor that is the problem, but rather that there is just more fuel being poured through the engine than what the sensor can correct for.

Good luck.