2002 S60 high fuel pressure

[wrgallant]

Another oddity - the return line does not seem to connect to anything. Just dumps over the tank.
Is that where excess pressure is supposed to be returned?

[wrgallant]

Another strange thing is that the non-pressure line to the pump doesn't seem to connect to anything.
Just dumps above the tank.

[wrgallant]

There's a relief valve right inside the pump in your model year, it releases the excess of pressure developed by the pump.

"Car seems to run fine" - but very rich. It will throw a code, if not already.

Any idea why my pump is not releasing excess pressure? I’ve tried 3 different pumps all with the same result.

[vtl]

Any idea why my pump is not releasing excess pressure? I’ve tried 3 different pumps all with the same result.

Do you have an OBD-II scan tool? Check the fuel trims, both short term (STFT) and long term (LTFT). Report back. If the ECU thinks its too much fuel, it will move the fuel trims to compensate.

[wrgallant]

Short term is 14.1%
Long term is -16.4%

[vtl]

Short term is 14.1%
Long term is -16.4%

Interesting. LTFT is far on a negative side, this is expected with your fuel pressure. STFT is far on a positive side, this is unexpected. Was it taken on a cold car?

[wrgallant]

yes - cold at idle

[vtl]

Ok, can be ignore then. So, yes: either the fuel pressure is really high or the MAF is lying and the ECU has to compensate. Can you read air flow at idle?

[wrgallant]

Would that be mass air flow rate?

[vtl]

Would that be mass air flow rate?

Right. Also what's your idling speed? 800 or 650?