Idle fuel pressure

[MCP]

I have been chasing around misfires and lean/rich fuel trims on my car for the past year and have only recently got to attaching a fuel pressure gauge on the fuel supply line to the rail. The pressure reads around 63psi at idle with vacuum hose connected to the FPR and around 70psi with it disconnected. I have a 4 bar FPR, and was wondering if this points to an obvious problem and what that problem would be. I also have a walbro 450. Any help and imput is appreciated. Thanks.

[MetalMan]

4bar = 58psi, so that should be your fuel pressure with the vacuum line disconnected from FPR.
Assuming your idle vacuum is 20 in.Hg (9.8 psi), then with the vacuum line connected you should see ~48psi.

My conclusion is you're seeing too high of fuel pressure. I'm no expert, but this tells me either your fuel pump is out-flowing the FPR, or your return line cannot flow enough (due to blockage, kink, or otherwise).

[slow ride]

Do you have your 450 wired to a relay and then battery? People tend to overrun the stock FPR when running a direct wired 450.

[CJ_]

Yep same setup here, Walbro 450 4 bar fpr, 63psi on my inline fuel pressure gauge at idle.

The pump simply flows too much for the stock fpr/return system at idle

[vavJETTAw36]

Had a similar issue recently. Found that my return lines had a kink in the tank. Fixed the kink and it only dropped it 4 psi from 67psi. My final fix was to buy an adjustable FPR to lower the pressure to OEM spec: 58/51 psi


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[MCP]

The fuel pump is wired just like stock, and could this higher pressure cause misfires? And does the fuel pressure have to be within the 58/51 psi oem spec? Thanks

[CJ_]

What are your fuel trims? What codes do you have? Who did the tuning? Mine runs fine at 63psi at idle and my fuel trims are within spec but I'm tuned for it.

[MCP]

fuel trims are 0.6% and 0.4% idle, and 6.5% and 1.1% partials throttle, no codes at the moment, I am on a base file from daz

[vavJETTAw36]

fuel trims are 0.6% and 0.4% idle, and 6.5% and 1.1% partials throttle, no codes at the moment, I am on a base file from daz

Getting your fuel pressure is not going to enrichen those trims. However, the misfires are suspect. I would look at ignition.

[MCP]

Ill give it another look, on another note, does anybody know if the n75 from the 1.8t (audi,passat ect) is interchangeable with the 2.7t?