E39 540i fuel pressure issue?

[zohaibrose]

Hello my e39 guys, thought id do a fuel presure test on my 540i/6 non tu just to check up on the fuel system, well since i dont have a schrader valve i teed into the fuel supply line by the driver firewall, i was getting 41 psi at idle and about 46 psi when i quick snapped the throttle. i thought it was suppose to be at 50psi at idle. does this indicate a weak pump, filter or its 9 psi lower since the systems been teed into, i took a video of it here https://www.youtube.com/watch?v=26mv6-wxSWs

also gettin codes p1145 and p1470 not sure if thats related to it, ltfts are -2.3 percent for some reason which is kind of confusing since the lower fuel pressure would indicate a lean condition

[philly98540]

AFAIK all the non TU M62's route the fuel pressure regulator vacuum line to the manifold. So the fuel pressure should be 51 minus about 10 or 41psi +/-. The regulator is set to 51 psi, but the vacuum line reduces the pressure at idle. Yours looks good. You can take off the vac line to the FPR from the back side of the engine to verify 51.

The M62 TU routes the FPR vac line is differently. It goes to the air intake hose in front of the throttle body, so it does not see manifold vacuum. Fuel pressure should be 51 psi on these cars.

[edjack]

P1145 Solenoid Valve Running Losses Control Circuit Electrical

P1470 Leakage Diagnostic Pump Control Circuit Electrical

Sadly, you don't ID the model year. The '98 has a leak detection system, housed in the LR wheel well. There may be faults there.

A negative fuel trim indicates a rich condition, as if there are one or more leaky injectors, or the leak detection system is feeding fumes when not commanded.