P0172 and P0175 any ideas?

I have a 96 t-bird with a 3.6l v-6. getting obd codes 0172 and 0175. System too rich (bank 1) and system too rich (bank 2). Theres a rythmic thumping in the fuel tank. It cycles about every 5 seconds. Checked the fuel pressure with the engine idling and it reads 65 psi. This jumps up to 70 psi every time you here the thump in the fuel tank. Relieve the fuel pressure and cycle the fuel pump by turning the ignition key, but not starting the engine and the pressure reads 38 psi. Also holds the 38 psi for at least 5 minutes. While engine is idling remove the vacuum line from the pressure regulator and theres no change in pressure. I"m thinking faulty fuel pressure regulator. Just can't figure out where the thumping fits into all this. Is there some kind of max. pressure overide? Any thoughts or experiences would be greatly appreciated

I agree with the fuel pressure regulator idea, If your system has a return line is it restrictted? that would explain the high pressure and maybe the thumping noise. Is there alot of pressure when you remove the gas cap
If you leave the cap off does it change anything?

Good luck and keep us postted

Jeff

Thanks for the reply jeff. When you take the gas cap off there is no pressure and no changes in the thumping. Took the return fuel line off at the fuel rail. Blew compressed air through the line toward the pressure regulator (which is removed at this point) and it is clean. Then blew air toward the fuel tank and the air goes through to the tank but it did take quite a bit of pressure. Not sure if this is because of the length of the line and the fact that it has half a tank of fuel. The rig has 73,000 mi. on it so i'm going to replace the pressure regulator anyway and see what that does. Oh yeah i also put a vacuum gage to the regulator and nothing much seemed to happen I'll keep you posted as to the outcome.

snugmat

Snugmat-- sounds like the fuel pressure regulator is the culprit. With engine running at an idle, doing a fuel pressure check when you remove and apply vacuum to the regulator should result in a pressure difference in specs with the book. Attach a line from the regulator to a empty bucket for a temporary return line to make sure the factory return line is ok and not restricted which would make pressures too high

OK heres the deal. Replaced the pressure regulator with no change. So i tore into the lines and the tank. Found that the plastic fuel return line was being pinched by the hose clamp that holds the fuel filter into its housing. Evidently whoever changed the fuel filter did'nt take the metal housing off the frame. You can do this by detatching the fuel lines , removing the hose clamp and sliding the filter out of it's nest. However when you put the new filter in you better be very careful sliding the hose clamp back through to secure the filter because it is real easy to get the return line inside the clamp. Best way is to pull the whole housing off the frame. Codes are gone and no more thumping in the fuel tank. Oh and the pressure is back where it belongs. Hope this helps someone in the future.