DA40 flight instructor with student reports a low fuel pressure indication at 9;000 FT and elected to return to the departure airport for a precautionary landing.

Narrative

I was flying the DA40-180cs Diamond Star with my instrument student on an instructional flight. We had previously gotten a weather briefing and filed an IFR flight plan. While we were en-route at 9;000 FT MSL; we noticed a Low Fuel Pressure Annunciator come on. I immediately went through the checklist and went through the troubleshooting. At this point I decided to divert back to our departure airport. I asked for a right hand turn vector to 270 degrees in order to return back to the airport. The Approach Controller had me descend to the following altitudes of 7;000; 3;000; and 1;500 FT in order to avoid wake turbulence from departing aircraft. When I was I was able to see the airfield I asked for a visual approach. The Controller asked how many gallons and souls were on board and stated that there would be fire trucks waiting on the taxiway as a precaution for me. I told the Controller that there were 35 gallons on board; two souls; and thank you for the assistance. I was able to safely land the airplane back to the return airport. One of the fire trucks followed me to the parking spot back at the FBO. I thanked the Controller for the assistance; shut down the airplane; and downed the aircraft for a maintenance inspection.