Thread: Fuel pressure drop problem

Hey guys, i am having some trouble figuring out exactly why my fuel pressure is dropping after a couple seconds after the fuel pump is done energizing. I have a walbro 255, aeromotive AFPR, JGY fuel rail and 370cc injectors. I Know that after you energize the fuel pump or shut the vehicle off, the fuel pressure should be dropping very slowly, not almost immediately like mine currently is. The car is running lean at idle(850+/- 75) at 18:1 or leaner. Cruising the afr will variate between 14-16afr depending on throttle position. At WOT the car leans out and stays around 14.5/15:1. I did hook up consult 2 to the vehicle and was able to add 10-15% more fuel and my idle smoothed out(still around 850) and my WOT AFR was right around 12.5:1 which was perfect.

The almost immediate fuel pressure drop would lead me to think i have a leaking injector but the wideband AND consult 2 beg to differ, both showing lean conditions. Let me know what you guys think, and if you need any more information about my car i will answer any questions!

I think most people's fuel systems do this...there's been a thread on this before iirc. Mine does it and it runs fine.

what ecu? 3 bar or 4 bar tune? and yes most fuel systems prime and drop about 10psi from personal experience.

its a JWT ecu, i have a GSPEC afpr.

sounds like the tune is just off because i have seen a few peoples cars do this and the air fuels have been fine

my main question is, Should the fuel pressure drop down to 0 as soon as the fuel pump turns off? From my experience working on Nissans the pressure will drop down over a period of 30 minutes or a little less. But if the pressure does drop down very fast after the pump is turned off, that means the regulator is bleeding fuel past itself

last time this came up i think it was said the check ball in the pump is whats to blame....could be wrong tho
think it was Teal97 that was having this issue also

I do have a walbro 255 installed in the car