symptoms of a worn injection pump?

[wjbski]

I looked at a '91 Jetta 1.6NA today. The car is in overall decent shape, it would be a decent daily driver, nothing else. It has a few typical MKII issues, nothing too suprising. During the test drive, the owner tells me he pulls a constant 42 MPG in combined driving.  This seems a little low to me.

The Bentley says something to the effect that anything below 44MPG is a sign of a worn injection pump. This car didn't spit out black smoke upon acceleration. It also seemed to idle a little high. The owner told me that when he runs the AC, he will pull the cold start lever to increase the idle speed to compensate for the AC compressor running. He tells me that the car doesn't belch out black smoke when he does this, which makes me think the car is running very lean.

The car has a relatively new T-belt. There aren't any reciepts showing a pump rebuild, so I'd guess it the original pump. The ODO is showing 284K on it.

Any thoghts about this car?  I've been reading through the different threads about pump mods, so it seems that if this car is running lean, it shouldn't hurt anything.

Thanks for any help.

[RabbitJockey]

diesel don't run lean or rich, more fuel and they accelerate less fuel and they decelerate, the only time it's bad for motor is when it gets too much fuel, you can call it rich if you want but it's not really, well it is but you know haha, jsut because the motor gets hot. i'd say 42 mpg is pretty normal, i think at 286k though it could probably use a rebuild, but also it could have a fairly worn engine (not too worn if it is doeing 42mpg)  i think over al it sounds like a good car, and i wouldn't be too concerned