I am in process of doing injector swap. So while in there pulled runners, thermostat cleaned up etc.

Car before hand was lean even with tuning in more BPW. 1 plug was lean others were normal to lean and 2 were rich.

FP always worked, just replaced fuel pump, relay, new gas tank, flushed lines but did not change injectors or FPR diaphragm

So prior to rebuild the fuel pressure while running with vac on would crank to 40-43psi then sit around 36-38psi. once I turned off it would bleed down to 30psi fairly quickly then below 20 in less then 20 minutes.

At prime with just key on only (cant remember if tested) I think it would do 42 then immediately drop to hi 30 then bleed down like above.


Now after cleaning everything and tight, I have no reinstalled the runners I wanted to check for leaks. The pump primes and hist 43+psi but immediatly drops to 30psi it stays there between 30-28psi. holding the return line or supply doesn't seem to do anything, pressure remains the same, but again this is just with the 2 sec prime, car is not back to together, so the pump is not pumping. I can drive the pump it is a new walpro 255 I suspect it will easily hit 43+psi


1: while at 30psi I observe no leaks at all anywhere. I did notice when I reassembled the fuel return line flare nut the rubber oring fell out and was trashed. I still tighten things down and I see no leaks. What is part to replace these orings and I can not imagine that this is the leak since I would see some fuel if it dropped 10+psi across it? is it safe to rune return with no oring?

2: anyone see FPR diaphram failure like this. where it is not broke since no gas is coming out the vac port but the spring is worn/old/stuck and can only hold 20-30psi with no vac? I think when I checked running at 17-20" of vac it is a different story and the vac masked the FPR weakness and sat at 38psi but this could explain my lean idle condition?

if I had a leak across the lines or at the fuel rails connections (which seem loose at reassembly but I tightend all down and reinstalled super snug. I would see weeping or pissing gas would I not?

I see nothing bone dry everywhere and pump primes no problem. Rest of the fuel system, injectors even radiator where all gummed up, gas was solid and orange, injectors were rusted at tips and the FPR is the only original thing, so I am hoping that is it and not some leak or bad new fuel pump or something else.