Air in the fuel

[Mattg]

I've got a 94 golf and I can see air bubbles in the fuel line coming out of the fuel filter.  I was told it was the pre heater and it wasn't a good thing.

What's the problem and how to I fix it?

[burn_your_money]

It could be alot of things. The most common is a loose fitting, then a restriction in the line somewhere (possible the fuel filter) and then the o-ring on the pre-heater on the fuel filter.

I'd start with a new FF if you don't know how old it is and then the o-ring and then the lines